When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Okay. Trying to track down some battery drain on my 1988 S4 (I leave it on a maintainer so I don't typically end up with a drained battery)
Anyhow....I set my el cheapo HF Multimeter to measure the draw from the battery. Passenger Door and Rear Hatch pin unplugged so as to not trigger interior lights/cause extra draw when testing.
I pulled the fuses for Fuse 6 and Fuse 20. I know the Power Seat may be an issue with memory or something. I am going to be pulling that seat to recover so I'll try to make sure things are cleaned up.
My draw is down to .50 - .55. I assume this is still a little high but not nearly as bad as 3x this amount. Any idea what is optimal?
Also, any advice in chasing down the HVAC draw? I have not pulled any relays to see if this further lowers the draw (or not)?
The correct way to test is with the doors closed and locked and the alarm armed- the current draw then should be around 30 mA if my memory serves correctly- that if everything is as it should be.
As to why your a/c is drawing 9 amps I have no idea- the clutch should take about 4 amps when it is energised but that should not be the case. Maybe you have relay issues.
with the following removed, the draw was .27 -
- 1. HVAC Controller (Fuse 6)
- 2. Driver Side Power Seat (Fuse 20)
- 3. Window Winder (Relay 6)
- 4. X Relay (Relay 4)
1. My biggest offender is the HVAC Controller - anyone have any experience with how much this SHOULD draw at rest?
2. I believe this could be memory related. I don't mind leaving the fuse undone as I don't really ever change this seat but as mentioned previously, I'll go through it when I remove it for recovering.
3 & 4 - Do you potentially explore a different relay or how does one start to try to resolve (especially the X Relay)?
The correct way to test is with the doors closed and locked and the alarm armed- the current draw then should be around 30 mA if my memory serves correctly- that if everything is as it should be.
As to why your a/c is drawing 9 amps I have no idea- the clutch should take about 4 amps when it is energised but that should not be the case. Maybe you have relay issues.
Thanks. I have no alarm on the car. Door pin for passenger and rear hatch are disabled so there's no difference right? I did the relay swap on the HVAC head unit... not sure if that would cause additional draw.
Do your interior lights work correctly in the door triggered mode? if not you must fix that first. The doors detected as opened (ignition off) turns off the interior light relay and has an effect on the alarm (are you sure you have NO alarm - or has it simply been disabled?)
Remove the X-Bus relay (NOT the relay in position X) with the HVAC fuse in - does your current draw go away on HVAC without the relay?
Do your interior lights work correctly in the door triggered mode?
Yes, they do. I simply disconnected the two wire junction at the hatch receiver and unscrewed the door pin switch so it would not ground (show as open)
Originally Posted by Alan
The doors detected as opened (ignition off) turns off the interior light relay and has an effect on the alarm (are you sure you have NO alarm - or has it simply been disabled?)
I am fairly sure I have no alarm but I'll investigate.
Originally Posted by Alan
Remove the X-Bus relay (NOT the relay in position X) with the HVAC fuse in - does your current draw go away on HVAC without the relay?
First - you are testing with ignition off, HVAC fuse installed and see current go away when you remove the X-Bus relay (for your year: Relay IV).
OK then this most likely means the X-Bus relay isn't turning off with the ignition off - this can be just a sticky relay (contacts 'welded' together). Try a new relay - the X-Relay for this year is a standard Bosch SPST relay, you can swap in the Horn relay to test.
The relay is controlled quite simply by the ignition switch X terminal, if the relay is good then the ignition switch is the next candidate to check.
First - you are testing with ignition off, HVAC fuse installed and see current go away when you remove the X-Bus relay (for your year: Relay IV).
OK then this most likely means the X-Bus relay isn't turning off with the ignition off - this can be just a sticky relay (contacts 'welded' together). Try a new relay - the X-Relay for this year is a standard Bosch SPST relay, you can swap in the Horn relay to test.
The relay is controlled quite simply by the ignition switch X terminal, if the relay is good then the ignition switch is the next candidate to check.
Try the alternate relay first.
Alan
Will do - even though I already put in a brand new relay from 928 intl. I'm thinking ignition switch THOUGH because of my other thread...
So pull the X-Relay - check the relay terminal in the now empty relay socket that would connect to relay pin 86 (you can use a male 1/4" Quick Connect Terminal for this). When the ignition switch is in position 0 (Off) this should not show any voltage to ground, with the ignition switch in positions 1 & 2 (Accessory & Ignition) it should show battery voltage and in position 3 (Start) it should show no voltage. Test to see what happens. You could do this with the start relay too - voltage expected only in position 3 (Start) - repeat to see it always works reliably.
So pull the X-Relay - check the relay terminal in the now empty relay socket that would connect to relay pin 86 (you can use a male 1/4" Quick Connect Terminal for this). When the ignition switch is in position 0 (Off) this should not show any voltage to ground, with the ignition switch in positions 1 & 2 (Accessory & Ignition) it should show battery voltage and in position 3 (Start) it should show no voltage. Test to see what happens. You could do this with the start relay too - voltage expected only in position 3 (Start) - repeat to see it always works reliably.
Alan
Okay. So XBus Relay and adjacent Relay are measuring 20F warmer than the other relays. I assume this was due to having a battery tender on and the erroneous "always on" nature of the X-Relay. Upon removal of the X-relay, I tested voltage on pin 86 at position 0 and it was battery voltage (12.6+). This voltage level was measured for positions 1 and 2, 3.
The starter relay behaved as expected. I am going to pull the Central Electric Panel and undo (not sure it is entirely relevant to this issue with the X-Bus) what I did when replacing my Central Electric Panel a couple of months ago.
Originally Posted by jej3
Same exact wiring but slightly different scheme in 1-5. All Bottom grey wires (b1-b5) below trace to the same destination as a1 through a5 on the original CE panel.
I am modifying the replacement by moving the yellow/black wire from b2 to b4. I'm taking the bus (heavy red) wire from a2 and moving it to the replacement board and connecting to b2. I will also pull the jumper wire from a1/a3 and moving it to b1/b3.
I do not believe sockets b1, b3, and b4 would have power otherwise as the 12v into the fuse is through those empty posts. The jumper from a1 to a3 is interesting and implies that either fuse 1 or 3 gets 12v in through the bottom and the jumper transfers 12v from one fuse to the other.
Stay tuned
Appreciate the ongoing advice. Would the ignition switch be the culprit if I am getting correct voltage on pin 86 at the starter relay (0 volts until ignition switch position 3)?
I just went back and re-read my CE thread and missed Alan's last comment there....
Originally Posted by Alan
The red wire on your car is an issue - it should not be there. Where does it go to? the input bus (30) (battery power) on the top of the CE panel? Someone did something weird here! This single connection may mean either your X bus is always live...?
Alan
I am in the process of reverting the wiring on the replacement CE to be as it arrived from 928Intl and NOT a replica of the original. This means removing (essentially unplugging and wrapping in electrical tape for a potential future feed for a to-be-fused future circuit) and removing the small jumper wire, which Alan offers is redundant -- AND I BELIEVE HIM
Originally Posted by Alan
The new CE panel (without the red wire) will certainly restore what is supposed to be the standard configuration. If your cigar lighter is always active the wire between fuse 1 & 3 is there for a particular reason - else it is completely redundant on your car. 928's should not be wired this way according to the WSM - but we already know of always powered cigar lighters.... this would be how to do it. Personally I think a switched cigar lighter is indeed better - e.g. you can plug in a radar detector and it comes on/off with the ignition, nothing left plugged in is at risk of draining the battery.
Alan
Hopefully this resolves the X-Bus always on and the larger drain. I'll still come back and report if it fixes plus what other AMP drains are still there.
1. AMP draw with CE Panel corrected is .09
2. X-Bus is no longer seeing 12volts at Position 0 or 3 on Ignition Switch
3. Central Locking is now working again!
Now, I do have the fuse for the driver seat removed as I believe I am going to have to troubleshoot with the seat out of the car.
Based on what I've read from others, is .09 amps a negligible amount of draw for a car which isn't likely to be parked for extended periods of time without battery tending. Would you agree?
If I do keep chasing this, I would start with these three....
What Bill said... You have a max of about 60 hours between chargings, however you plan to do that. And hope that the engine starts really fast and doesn't drag the battery down during cranking. That alone should be adequate incentive to find and solve the remaining drains.
02-23-2020, 04:27 PM
Tracing Amp Draw
