We've had a 928 fire, and here's what we learned...
05-12-2020, 01:01 PM
#196
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It has been said that Porsche deliberately chose an insulation for the wiring harnesses that would recycle easily when time came to do that. It seems the really good insulation was too hard to remove form the wires when recycling? I find that hard to believe, and I tend to think perhaps it was a planned obsolescence design.
But, for whatever reason they chose the insulation they did, it is very clear to all of us that the insulation on our wires is cracking and falling off now. Engine wiring harnesses, ABS wiring harnesses, and injector wiring harnesses seem most at risk due to the heat, oil, and ozone (alternators create ozone) found in a engine compartment. Other harnesses around the car are failing too - but IMO not at the same rate as the under-hood ones.
SO: I wrote this thread to tell you what I learned. I do not care if you buy our product or come up with your own solution like some here who have installed cut-off switches. Whatever works for you. But please do something to protect your Porsche from a sudden electrical fire. Especially if your garage is attached to your house!
But, for whatever reason they chose the insulation they did, it is very clear to all of us that the insulation on our wires is cracking and falling off now. Engine wiring harnesses, ABS wiring harnesses, and injector wiring harnesses seem most at risk due to the heat, oil, and ozone (alternators create ozone) found in a engine compartment. Other harnesses around the car are failing too - but IMO not at the same rate as the under-hood ones.
SO: I wrote this thread to tell you what I learned. I do not care if you buy our product or come up with your own solution like some here who have installed cut-off switches. Whatever works for you. But please do something to protect your Porsche from a sudden electrical fire. Especially if your garage is attached to your house!
05-12-2020, 01:03 PM
#197
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yup, mine was cracked.
I used that Self-amalgamating tape and added a few wraps to it. Also painted that damn screw top red as a reminder that this is a hot circuit. I found that out early in ownership when i decided to make sure that the screw was tight......of course the edge of the screw driver touched the fender..sparked..glowed and then IT became very tight to remove
. It was a split second but felt like an eternity as it began to weld itself to the car.
I used that Self-amalgamating tape and added a few wraps to it. Also painted that damn screw top red as a reminder that this is a hot circuit. I found that out early in ownership when i decided to make sure that the screw was tight......of course the edge of the screw driver touched the fender..sparked..glowed and then IT became very tight to remove
. It was a split second but felt like an eternity as it began to weld itself to the car.You cannot beat bombing along at night, wife and two kids in the car, outside lane overtaking all and sundy on a busy 3 lane motorway and then weld the battery to the compartment lid- no engine, no lights, no indicators, no windows and rapidly bleeding the speed I had- somehow managed to barge my way across 3 lanes, pull over to the hard shoulder and then pee myself! Silly sod forgot to fasten the battery mount! Better still, it was a brand new battery and that was well and truly buggered. Took it back to the shop I got it from, showed them the warranty and told them there was something wrong with the battery. They gave me a replacement. Did not tell them any lies- honesty pays!
05-12-2020, 03:23 PM
#198
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My thumbnail number was from the 600 CCA common for this family of batteries, more for easy illustration of the amount of total energy dissipated as heat. That number ASSumes that it's supplying above 10V to a starter motor, so your 1KA number for a functionally few-volts load may still be a little conservative. You do have the resistance in the KS2 FOE harness pieces to consider in the analysis. Regardless, with that kind of fault current available, plastic insulation won't offer much protection regardless of whether it's environmentally sensitive or some extreme-temps-capable unobtanium compound. Care and quality of workmanship are critical, as are material and connector choices when doing any work on electrics. Ideally, every circuit would be fused at the source, but "the source" is split between battery in the rear and alternator front left. Fuses and circuit breakers are sized and placed to protect wiring in the car. Period. 100% foolproof doesn't happen with all the wiring and circuits in our cars either. Take a look at Alan's pics of battery box accessory wiring for clues. Anyway, the system is always a compromise. Failure modes include no operation and/or damaged wiring.
05-12-2020, 04:23 PM
#199
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However post-'95 there are many, many documented issues with German car wiring harnesses. 986 and 996 harnesses are notorious attracters of rodents if stored for any length of time. I think the most infamous is the E-class Mercedes W210 (1996–2002) where the engine wiring harness disintegrated in absolutely no more than 10 years regardless of rodents or storage.
I find that hard to believe, and I tend to think perhaps it was a planned obsolescence design.
But, for whatever reason they chose the insulation they did, it is very clear to all of us that the insulation on our wires is cracking and falling off now. Engine wiring harnesses, ABS wiring harnesses, and injector wiring harnesses seem most at risk due to the heat, oil, and ozone (alternators create ozone) found in a engine compartment. Other harnesses around the car are failing too - but IMO not at the same rate as the under-hood ones.
From what I've seen, *so far*, with the exception of the front-main harness (starter to jump post), "wire harness issues" are the result of handling or mechanical damage not degradation. Obviously the more they degrade the less handling they can survive without becoming a problem. The harnesses are between 25 and 42 years old now. I think that a ~30-year lifetime is about as good as one could reasonably expect.
Nevertheless, regardless, and obviously, there will be a need for replacement harnesses for any 928 who's owner wants to keep it on the road. Again from what I've seen, the wheel-well ABS/PW/RDK harnesses(*) are "next" along with the injection harness. Any harness in the vicinity of current or past mechanical damage becomes a candidate for replacement if not, at least, very close examination.
(*) '94s and '95s have no wheel well harnesses. It is a single harness for the whole car. Not going to be fun to replace when it's time.
05-12-2020, 04:51 PM
#200
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My thumbnail number was from the 600 CCA common for this family of batteries, more for easy illustration of the amount of total energy dissipated as heat. That number ASSumes that it's supplying above 10V to a starter motor, so your 1KA number for a functionally few-volts load may still be a little conservative. You do have the resistance in the KS2 FOE harness pieces to consider in the analysis. Regardless, with that kind of fault current available, plastic insulation won't offer much protection regardless of whether it's environmentally sensitive or some extreme-temps-capable unobtanium compound. Care and quality of workmanship are critical, as are material and connector choices when doing any work on electrics. Ideally, every circuit would be fused at the source, but "the source" is split between battery in the rear and alternator front left. Fuses and circuit breakers are sized and placed to protect wiring in the car. Period. 100% foolproof doesn't happen with all the wiring and circuits in our cars either. Take a look at Alan's pics of battery box accessory wiring for clues. Anyway, the system is always a compromise. Failure modes include no operation and/or damaged wiring.
The numbers serve to illustrate the point that prevention is better than protection. Most rank and file owners probably have little clue about the energy potential of their battery. Remember CCA is what the battery can turn out at minus whatever degrees they are rated at- In a garage during summer that number shoots up but whatever the value it is huge and potentially devastating. I actually modelled the system to determine the ampage potential at that location- it was huge given the trunk size feeding the starter- a very potent heater!
Try to stop the problem from happening by ensuring the cabling and connections are in decent condition and the probability of such failure drops dramatically. Carl was singularly unlucky with this incident and the real learning value for our professionals [and owners?] in general is to disconnect the battery of vehicles whilst stored in their care and left unattended albeit it is a PITA.
On the other hand the starting amps is somewhere in the region of 300 amps so primary protection would have to be at least 10% greater than this number- 330 amps? Earth leakage at 329 amps can do an awful lot of damage considering a small welding machine can function nicely on 50 amps. Assuming 50 amps is enough to have burnt a hole in the steel chassis as per this example perhaps what practical use is a fast acting fuse rated at 330 amps? In reality it is little more than peace of mind thus why I concluded that Porsche engineers did not fuse such.
On a separate point I noted with interest your observation that some of the users acted upon from the Central electric panel are not fused. I found that rather alarming/astonishing. I have never carried out an audit of the fuse panel- simply figured that one way or another all end users are fused. Must take a look into that one of these days if i can figure out the diagrams. Perhaps you might be kind enough to cite a couple of examples so I know where to start looking.
05-12-2020, 07:07 PM
#201
Photos can never give a meaningful evaluation of the viability of the engine loom unless of course the cables are thread bare but the discolouration is a good start- that and practical experience. A bit of localised damage can always be patched up with tape or whatever. Flex the cable back and forth a few times and if you see cracking of the insulation then it is toast. I use the term "welding machine" because that in effect is what one has if the feeders are falsely grounded- if you want to see the effect I think I posted a video link earlier in the thread. Dr Bob mentions 600 amps, I calculated over a 1000 amps potential depending on what section was considered but whatever number one chooses to work with that is a lot of kilowatts on the loose.
The engine loom is not too difficult to remove- you have to undo connections at the starter motor, the alternator, the hot post and the ABS for the power cables. There are about 10 cables that emanate from the 14 pin connector and several support positions along the front of the motor. The loom runs through the front casing under the cam wheel housing and drops down to the alternator. As one progresses along the loom cables for the various accessories leave the assembly. The heat shrink by now is like bakellite and is as much a hazard as it is a protection. Initially I undid everything in the front of the engine and cut the heat shrink off to get an idea of what condition the cables were in. I then decided the job lot was coming out and disconnected everything inboard of the engine. Take plenty of photos to help you recall the routing. In my case I found the power cables were in bad shape under the orange protective sheath close to the alternator and the starter motor. The feeder from the battery to the starter motor seemed Ok. In my case what started the hunt was when I had problems with the oil pressure indication on the panel- those cables were almost non existant! The more I examined the worse it got.
I decided to rebuild the harness myself but it is not a small undertaking and one also has to recognise the potential of the consequences of a crimped joint failing. If I was going to fit a MCB device it would be on the feed to the central electrics panel just as Dr Bob suggests and a 60 amp rating sounds like a good number. On the S4 and later models the power is delivered via two 10mm2 cables from the hot post to the CE. On my GTS those cables seemed to be in good condition so they are still original. The fire in the car this thread is about started in one of those two cables or so it would seem looking at the hole burnt in the steel frame. I put additional layers of heat shrink over those cables before they disappeared into the main body of that loom.
The engine loom is not too difficult to remove- you have to undo connections at the starter motor, the alternator, the hot post and the ABS for the power cables. There are about 10 cables that emanate from the 14 pin connector and several support positions along the front of the motor. The loom runs through the front casing under the cam wheel housing and drops down to the alternator. As one progresses along the loom cables for the various accessories leave the assembly. The heat shrink by now is like bakellite and is as much a hazard as it is a protection. Initially I undid everything in the front of the engine and cut the heat shrink off to get an idea of what condition the cables were in. I then decided the job lot was coming out and disconnected everything inboard of the engine. Take plenty of photos to help you recall the routing. In my case I found the power cables were in bad shape under the orange protective sheath close to the alternator and the starter motor. The feeder from the battery to the starter motor seemed Ok. In my case what started the hunt was when I had problems with the oil pressure indication on the panel- those cables were almost non existant! The more I examined the worse it got.
I decided to rebuild the harness myself but it is not a small undertaking and one also has to recognise the potential of the consequences of a crimped joint failing. If I was going to fit a MCB device it would be on the feed to the central electrics panel just as Dr Bob suggests and a 60 amp rating sounds like a good number. On the S4 and later models the power is delivered via two 10mm2 cables from the hot post to the CE. On my GTS those cables seemed to be in good condition so they are still original. The fire in the car this thread is about started in one of those two cables or so it would seem looking at the hole burnt in the steel frame. I put additional layers of heat shrink over those cables before they disappeared into the main body of that loom.
05-12-2020, 07:55 PM
#202
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Hi Fred, I really appreciate your informed response.. I cant claim to be an expert with my 928 electrical system as fortunately ive never had to be but, since both of them have gotten older, I am being forced to take alot more interest. In your opinion, am i doing the right thing here, replacing the FOE harness as made by Sean and then putting in a fuse by battery. I can get a similar aftermarket system locally that is very similar to the Audi set up and it just about fits in. It can do a 200 amp mega fuse for the main line from the battery and it has 3 additional terminals for the smaller wires which can go as high as 10 or 15 amps. Please forgive my ignorance with all this, im wary of wiring and also im not sure where everything goes, so a couple of questions that may have been answered already. What are the additional wires for that run from the battery and where do they go, secondly, the car that caught fire at Carl's, you said had a problem with the harness that went forward from the jump post. The replacement 'Sean' harness doesn't replace those does it ? if this is the case, is there a separate harness that goes from the jump post to the CE or can I simply use plenty of the Vulcanising tape to deal with this problem ??? AM I overreacting to a problem that i might not have ? I would rather my beautiful S4 didn't go up in smoke. So many questions sorry. Cheers. AL
Inspection is your friend. The engine harness is particularly vulnerable due to the heat and timeline but there are other components to the system end to end like the two 10mm2 cables leading to the central electrics that are looking somewhat suspect in your engine bay. As a minimum they clearly need something doing to them and now even if it is just a localised repair. Once those cables enter the main sleeving you may well find they are in much better condition- so you can open the sleeving for a couple of run inches and take a peek to see how they are getting on in there. If the cable colours are not discernible then it is probably time to replace them.
Of the cables in the 14 pin connector only two are "critical"- terminal 1 blue is the alternator exciter wire- terminal 14 is yellow 4mm2 and is the cable to fire up the starter motor solenoid. Getting the critical cables secure is the prime mission but having all the harness sorted is the real way to go plus whatever else is needed to be done. Inspecting the cables at the alternator and the starter motor is relatively easy once the car is in the air.
Self vulcanising tape is useful but I do not rate it or specifically the material I have. Heat shrink is a useful addition and the best external protection is the orange coated fibre glass sleeving in and around the alternator/starter motor area. Even cheap and nasty insulation tape is better than nothing if the insulation is shot- albeit it will not last long in the heat.
As I noted earlier, I have nothing specifically against circuit protection but I feel it has very limited value and arguably no value at all depending on how one looks at the issue. If I were to protect anything it would be the feed to the central electrics but I have little in the way of motivation to do anything- just my point of view.
So get in there and post some pics in a separate thread..
I take the point of view that my 28 year old GTS has done quite well generally speaking but the harness was well shot when I got round to inspecting it about 3 years ago- scary may be a better description.
05-12-2020, 08:36 PM
#203
Hi Fred, Thanks. Ill get some photos and start a thread. I was trying to avoid re inventing the wheel though, however, it may be a good idea. Im just a little nervous now that ive seen all these scary stories ! Its good that the harness can be done in stages though, I haven't had any electrical malfunctions so far and I certainly don't want them to start now.
By the way, you car looks AWESOME !
By the way, you car looks AWESOME !
05-12-2020, 09:29 PM
#204
Chronic Tool Dropper
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Bob,
The numbers serve to illustrate the point that prevention is better than protection. Most rank and file owners probably have little clue about the energy potential of their battery. Remember CCA is what the battery can turn out at minus whatever degrees they are rated at- In a garage during summer that number shoots up but whatever the value it is huge and potentially devastating. I actually modelled the system to determine the ampage potential at that location- it was huge given the trunk size feeding the starter- a very potent heater!
Try to stop the problem from happening by ensuring the cabling and connections are in decent condition and the probability of such failure drops dramatically. Carl was singularly unlucky with this incident and the real learning value for our professionals [and owners?] in general is to disconnect the battery of vehicles whilst stored in their care and left unattended albeit it is a PITA.
On the other hand the starting amps is somewhere in the region of 300 amps so primary protection would have to be at least 10% greater than this number- 330 amps? Earth leakage at 329 amps can do an awful lot of damage considering a small welding machine can function nicely on 50 amps. Assuming 50 amps is enough to have burnt a hole in the steel chassis as per this example perhaps what practical use is a fast acting fuse rated at 330 amps? In reality it is little more than peace of mind thus why I concluded that Porsche engineers did not fuse such.
On a separate point I noted with interest your observation that some of the users acted upon from the Central electric panel are not fused. I found that rather alarming/astonishing. I have never carried out an audit of the fuse panel- simply figured that one way or another all end users are fused. Must take a look into that one of these days if i can figure out the diagrams. Perhaps you might be kind enough to cite a couple of examples so I know where to start looking.
The numbers serve to illustrate the point that prevention is better than protection. Most rank and file owners probably have little clue about the energy potential of their battery. Remember CCA is what the battery can turn out at minus whatever degrees they are rated at- In a garage during summer that number shoots up but whatever the value it is huge and potentially devastating. I actually modelled the system to determine the ampage potential at that location- it was huge given the trunk size feeding the starter- a very potent heater!
Try to stop the problem from happening by ensuring the cabling and connections are in decent condition and the probability of such failure drops dramatically. Carl was singularly unlucky with this incident and the real learning value for our professionals [and owners?] in general is to disconnect the battery of vehicles whilst stored in their care and left unattended albeit it is a PITA.
On the other hand the starting amps is somewhere in the region of 300 amps so primary protection would have to be at least 10% greater than this number- 330 amps? Earth leakage at 329 amps can do an awful lot of damage considering a small welding machine can function nicely on 50 amps. Assuming 50 amps is enough to have burnt a hole in the steel chassis as per this example perhaps what practical use is a fast acting fuse rated at 330 amps? In reality it is little more than peace of mind thus why I concluded that Porsche engineers did not fuse such.
On a separate point I noted with interest your observation that some of the users acted upon from the Central electric panel are not fused. I found that rather alarming/astonishing. I have never carried out an audit of the fuse panel- simply figured that one way or another all end users are fused. Must take a look into that one of these days if i can figure out the diagrams. Perhaps you might be kind enough to cite a couple of examples so I know where to start looking.
Hi Fred --
The most egregious example is probably the fuel injectors, which get unfused battery positive post power for a dedicated feeder from the battery through a relay. Unfused 30-bus power from the feeder under question includes circuits to the hi-beam and headlight switches, with load circuits protected only after the relays. Circuit feeds the fan and flaps controller next to the passenger's seat. The philosophy of fusing loads is commendable, but it leaves several wiring sections between CE and a switch or controller unprotected.
Then, consider owner or audio-shop additions for "upgrades" that tap off the easily-accessible 30 bus, or one of the wires that connect to it. More than a few times i get to see insulation that's been perforated by a test light probe, damaged by a ScotchLock connector piggy-backed on a red conductor big or small, to power something through a new wire not installed correctly or protected. There's enough to make you look twice.
Adding a 350 amp fuse to the primary feed to the starter might protect that primary feeder. Does nothing for any of the smaller primary wiring from there forward. There's no convenient or even serviceable place to add protection for the rest. As discussed previously, the primary feed should be large enough to be protected by that 350 amp fuse, so a 2ga from starter battery terminal directly to CE 30 would be strong enough. Add a fuse/breaker where that feeder attaches to the bus, sufficient to protect the bus and wire connected to it until smaller load fuses are fitted to protect the wiring to the final elements. All before any circuit exits the CE panel.
Not trying to reinvent anything, say that what we have is bad, or that our cars are all going to burn to the ground (sorry...) on their NNth birthday. Just that the system deserves respect for the amount of energy that can be converted before any protection kicks in.
05-13-2020, 03:26 AM
#205
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Hi Fred, Thanks. Ill get some photos and start a thread. I was trying to avoid re inventing the wheel though, however, it may be a good idea. Im just a little nervous now that ive seen all these scary stories ! Its good that the harness can be done in stages though, I haven't had any electrical malfunctions so far and I certainly don't want them to start now.
By the way, you car looks AWESOME !
By the way, you car looks AWESOME !
Being a "little nervous" is good- it means you are thinking! Risk is with us in every aspect of life [and now death!]. Worrying about it is generally pointless. Risk management is about getting the risks down to acceptable levels- even new cars have been known to burst into flames!
The 928 has several "ELE's" [extinction level events] viz:
1. Wiring fires
2. Thrust bearing failure [automatics]
3. Fires due to shot fuel lines
4. Fires due to high pressure power steering line failure.
5. Cooling system corrosion of the heads and block
Items 1 through 4 are manageable and all have been addressed on my 928 to the best of my abilities. Item 5 to date has no solution- I am currently working on that one best I can.
Remember: "Chance favours the prepared mind"! [Kipling]
05-13-2020, 03:35 AM
#206
Rennlist Member
Hi Fred --
The most egregious example is probably the fuel injectors, which get unfused battery positive post power for a dedicated feeder from the battery through a relay. Unfused 30-bus power from the feeder under question includes circuits to the hi-beam and headlight switches, with load circuits protected only after the relays. Circuit feeds the fan and flaps controller next to the passenger's seat. The philosophy of fusing loads is commendable, but it leaves several wiring sections between CE and a switch or controller unprotected.
Then, consider owner or audio-shop additions for "upgrades" that tap off the easily-accessible 30 bus, or one of the wires that connect to it. More than a few times i get to see insulation that's been perforated by a test light probe, damaged by a ScotchLock connector piggy-backed on a red conductor big or small, to power something through a new wire not installed correctly or protected. There's enough to make you look twice.
Adding a 350 amp fuse to the primary feed to the starter might protect that primary feeder. Does nothing for any of the smaller primary wiring from there forward. There's no convenient or even serviceable place to add protection for the rest. As discussed previously, the primary feed should be large enough to be protected by that 350 amp fuse, so a 2ga from starter battery terminal directly to CE 30 would be strong enough. Add a fuse/breaker where that feeder attaches to the bus, sufficient to protect the bus and wire connected to it until smaller load fuses are fitted to protect the wiring to the final elements. All before any circuit exits the CE panel.
Not trying to reinvent anything, say that what we have is bad, or that our cars are all going to burn to the ground (sorry...) on their NNth birthday. Just that the system deserves respect for the amount of energy that can be converted before any protection kicks in.
The most egregious example is probably the fuel injectors, which get unfused battery positive post power for a dedicated feeder from the battery through a relay. Unfused 30-bus power from the feeder under question includes circuits to the hi-beam and headlight switches, with load circuits protected only after the relays. Circuit feeds the fan and flaps controller next to the passenger's seat. The philosophy of fusing loads is commendable, but it leaves several wiring sections between CE and a switch or controller unprotected.
Then, consider owner or audio-shop additions for "upgrades" that tap off the easily-accessible 30 bus, or one of the wires that connect to it. More than a few times i get to see insulation that's been perforated by a test light probe, damaged by a ScotchLock connector piggy-backed on a red conductor big or small, to power something through a new wire not installed correctly or protected. There's enough to make you look twice.
Adding a 350 amp fuse to the primary feed to the starter might protect that primary feeder. Does nothing for any of the smaller primary wiring from there forward. There's no convenient or even serviceable place to add protection for the rest. As discussed previously, the primary feed should be large enough to be protected by that 350 amp fuse, so a 2ga from starter battery terminal directly to CE 30 would be strong enough. Add a fuse/breaker where that feeder attaches to the bus, sufficient to protect the bus and wire connected to it until smaller load fuses are fitted to protect the wiring to the final elements. All before any circuit exits the CE panel.
Not trying to reinvent anything, say that what we have is bad, or that our cars are all going to burn to the ground (sorry...) on their NNth birthday. Just that the system deserves respect for the amount of energy that can be converted before any protection kicks in.
Will look into the injector wiring thing when I get chance. The only point of note on that - a few years ago I saw degradation in the wiring and did a bit of a remedial intervention on 4 of the pigtails/connectors using kit from the wiring harness of my late 90S4. To my pleasant surprise I found that once I got into the main loom everything looked in tip top condition. That being said some of my injectors connectors are in less than stellar condition and I have 8 new connectors ready to splice in during the next inspection and maintenance intervention back end of this year.
Not too surprising it seems we are well aligned with respect to our thinking about the system in general. What i have in mind is to put a couple of in-line weatherproof fuses into those two 10mm2 lines exiting the hot post-. If 60 amps is the notional load then a 30 amp fuse in each line might serve a purpose- any thoughts?
Rgds
Fred
05-13-2020, 01:48 PM
#207
Chronic Tool Dropper
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Hi Fred --
When I guessed at the60 50 Amp protection, I was looking only at the wire sizes and protection needed for that section of wiring between the jump post and the CE panel. I pulled the breaker from the bin and shared the picture below. The purchase was on a whim, as I was looking at marine tinned ground strap options at Waytek on guidance from Alan Moore. There were the breakers! Cheap enough to risk with the guess. I really need to do a full-load test with a clamp around the feeder in the front of engine harness to see what the draw there really is with everything running and all the lights on. Base is 3" x 1.75", with 1/4" diameter posts. It's a manual-reset breaker with a manual-open option, and is intrinsically safe (enclosed contacts and no explosion/ignition hazard). They are available in a range of Amp ratings, so don't feel like my guess was the only available truth.
That said, a 30A fuse in each one might be a Good Start. Or a 30A thermal breaker in each one?
When I guessed at the
That said, a 30A fuse in each one might be a Good Start. Or a 30A thermal breaker in each one?
05-13-2020, 02:00 PM
#208
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Bob,
There is a lot to be said for something that can be reset in the blink of an eye- very elegant. Had there been such a device in that location coming out of the hot post then Carl would probably have had nothing to post about. Another optimal location might be coming out of the alternator but with the heat down there one would need something rated for 100C continuous exposure - urrgh!
Bottom line if one was going to install protection that is where my focus would be in terms of bang for the buck.
There is a lot to be said for something that can be reset in the blink of an eye- very elegant. Had there been such a device in that location coming out of the hot post then Carl would probably have had nothing to post about. Another optimal location might be coming out of the alternator but with the heat down there one would need something rated for 100C continuous exposure - urrgh!
Bottom line if one was going to install protection that is where my focus would be in terms of bang for the buck.
05-13-2020, 02:40 PM
#209
Electron Wrangler
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The 2 cooling fan feeders from the battery to the CE panel are not source fused which is a mistake - they exist to remove loading (voltage drop) and noise from the CE panel - but this is poorly implemented. Likewise the battery direct ECU and ABS controller feeders are not source fused - these direct connections are intended to reduce noise. These can mostly be rectified with a small auxiliary fuse panel at the battery - but this leads to double fusing for the cooling fans without additional CE panel modifications. Ideally the cooling fans would be fed more directly from the alternator (with dedicated wiring & fuses)
The dual feeders from the Jump post to the CE panel are a little problematic in my mind, really it should be a single larger fused feeder. If one of these feeders fails or is loose (they are just screwed to the CE panel) all the current goes through the other one, the voltage will drop and the wire will overheat (and you likely won't really notice anything much). There are many compromises in the architecture of the primary wiring, but it is actually generally implemented very well by Porsche on the as delivered vehicle - but then over time material degradation, poor maintenance/handling and aftermarket modifications create additional risks. There is only so much you can easily do without getting into extensive modifications. If you are going to change the primary wiring at all you need to be very sure you can implement it well - or you are just adding new risks.
Alan
The dual feeders from the Jump post to the CE panel are a little problematic in my mind, really it should be a single larger fused feeder. If one of these feeders fails or is loose (they are just screwed to the CE panel) all the current goes through the other one, the voltage will drop and the wire will overheat (and you likely won't really notice anything much). There are many compromises in the architecture of the primary wiring, but it is actually generally implemented very well by Porsche on the as delivered vehicle - but then over time material degradation, poor maintenance/handling and aftermarket modifications create additional risks. There is only so much you can easily do without getting into extensive modifications. If you are going to change the primary wiring at all you need to be very sure you can implement it well - or you are just adding new risks.
Alan
05-13-2020, 03:06 PM
#210
Drifting
There's a passive fire suppression system called 'BlazeCut'USA.com.... It's a 'hose' filled with 'HALON' ( I think) that you mount in the area you want to protect. When the temp. in the area exceeds the rated temp of the 'Hose' , It Bursts & releases The fire suppression chemical.....Putting out the fire....It's a "One-Shot' system, No wiring needed...Just install it & Forget it.. Google "BlazeCutUSA,com' for more info.