Heating System - 3.2 Carrera
08-15-2006, 02:08 AM
#1
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Heating System - 3.2 Carrera
I purchased an '88 3.2 recently and found that the heat cannot be turned off. I had the mechanic look at it, and he replaced some springs in the flaps that control the air from the engie, but the issue persists. The front air controls seem to be working, since I can direct the heat either up to the windshield (defrost) or down below by the footwell. Additionally, the 3-setting blower switch seems to do nothing (possible fuse issue?).
In any event, the manual says very little about these controls. Do I need to purchase the "Porsche 911 Carrera Service Manual 1984-1989" for $119 or is there someone who knows all about these systems?
I guess I should also mention that the fresh-air blower motor also does not seem to work, but the AC blower and system works fine, but as you can imagine, it gets pretty hot in the car during the summer.
In any event, the manual says very little about these controls. Do I need to purchase the "Porsche 911 Carrera Service Manual 1984-1989" for $119 or is there someone who knows all about these systems?
I guess I should also mention that the fresh-air blower motor also does not seem to work, but the AC blower and system works fine, but as you can imagine, it gets pretty hot in the car during the summer.
08-15-2006, 05:54 AM
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First of all, get the "Porsche 911 Carrera Service Manual 1984-1989", it is very good. You will not regret it.
The flapper boxes that control the air from the heat exchangers are prone to rust, so they can be stuck open. Also the wires from the control box between the seats can be stuck, or broken.
The reason why the blowers do not turn on is that you have to drive above a certain speed before they start. There is a switch inside the speedometer that controls this. The one on my car did open somewhere between 2500 and 3000 rpm. Why it happened at certain a rpm and not a speed I do not know, but that was before I fried that switch trying to circumvent it.
Does the electrical blower on the engine start when you twist the **** on the control box? The way to check that is to turn on the ignition, but not the engine, and twist the **** to the first postion. Then the engine compartment blower should start. You shold also be able to hear the flappers opening. They creak a little when the open and close.
/Peter
The flapper boxes that control the air from the heat exchangers are prone to rust, so they can be stuck open. Also the wires from the control box between the seats can be stuck, or broken.
The reason why the blowers do not turn on is that you have to drive above a certain speed before they start. There is a switch inside the speedometer that controls this. The one on my car did open somewhere between 2500 and 3000 rpm. Why it happened at certain a rpm and not a speed I do not know, but that was before I fried that switch trying to circumvent it.
Does the electrical blower on the engine start when you twist the **** on the control box? The way to check that is to turn on the ignition, but not the engine, and twist the **** to the first postion. Then the engine compartment blower should start. You shold also be able to hear the flappers opening. They creak a little when the open and close.
/Peter
08-16-2006, 11:18 AM
#3
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I did not know that you had to drive above a certain speed to turn on the blowers. That seems strange, if not counter-intuitive, since you probably need more heat when the car is stationary (less airflow from the engine due to idling). No, the blower doesn't start when i twist the ****. Not sure which blower you are referring to, since there are many, but neither the rear heater blower runs, nor the cold air blower. I opened the fuse box and re-seated the fuses, but that did nothing. I guess I'll have to wait until my book comes in so that I can understand what's happening here.
08-16-2006, 05:28 PM
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In your engine compartment, on top of the left intake runners there is an electrical blower that feeds air into the heat exchangers. That was the blower I was refering to. With the ignition on, it should start ones you twist the **** on the control box. I just checked on my car.
The engine compartment blower should start at standstill, but the footwell blowers starts above some speed. At least that was the case on my car. The manual says nothing about it though. Maybe Porsche didn't want people to die of carbon dioxide poisoning. The footwell blowers are located behind a panel in front of the door. There is one on each side.
After some searching through the wiring diagrams I found out how to jumper the control so that the blowers would start anyway. Not too difficult, just had to cut one wire in a connector in the engine compartment, solder it to another wire, and earth one wire.
Did you check the fuses in the engine compartment as well? There are a couple of them behind a plastic cover on the left side on the engine compartment wall. There are three fuses there, one for the heated rear window, one for the engine compartment blower and one for the footwell blowers.
/Peter
The engine compartment blower should start at standstill, but the footwell blowers starts above some speed. At least that was the case on my car. The manual says nothing about it though. Maybe Porsche didn't want people to die of carbon dioxide poisoning. The footwell blowers are located behind a panel in front of the door. There is one on each side.
After some searching through the wiring diagrams I found out how to jumper the control so that the blowers would start anyway. Not too difficult, just had to cut one wire in a connector in the engine compartment, solder it to another wire, and earth one wire.
Did you check the fuses in the engine compartment as well? There are a couple of them behind a plastic cover on the left side on the engine compartment wall. There are three fuses there, one for the heated rear window, one for the engine compartment blower and one for the footwell blowers.
/Peter
08-17-2006, 04:06 PM
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OK, here's what I've done so far:
1.) Located the rear blower in the engine compartment, remove it and found that it is completely shot - bearings have fallen out and wheen barely rotates. This motor will need to be replaced.
2.) Used contact cleaner on the rear fuse box, replaced 1 bad fuse and checked the remaining fuses with an ohmeter gague. They now all work.
3.) Checked power to the rear blower motor - 13V no problem when the switch is on, 0V when off.
4.) Opened up the front footwells and found both blown fuses. I will replace the fuses and then see if it works, but only after the rear motor has been replaced - since the rear has to work before the footwell ones work.
5.) Opened up, cleaned and tested all fuses in the front fuse box. They all work.
So, once I replace the rear blower, I will probably be OK. But actually, I'm still having the problem of heat coming through the vents in the car even when the flaps are off and the motor is off. So I got under the car to see the heater valves. Both valves are open and then close fine when the levers are pulled up and then back down. So how can all this heat still be coming in through the car? Both heater valves have the openings to allow the heat out of the car, but I'm guessing there is also a door that needs to be closed? Is that door hidden from view? I guess I'll get back under the car and adjust those cables to maximum off. Actually, there is quite a bit of heat even with no heater motors or blowers, so I might not even have to replace the blowers in the winter!
1.) Located the rear blower in the engine compartment, remove it and found that it is completely shot - bearings have fallen out and wheen barely rotates. This motor will need to be replaced.
2.) Used contact cleaner on the rear fuse box, replaced 1 bad fuse and checked the remaining fuses with an ohmeter gague. They now all work.
3.) Checked power to the rear blower motor - 13V no problem when the switch is on, 0V when off.
4.) Opened up the front footwells and found both blown fuses. I will replace the fuses and then see if it works, but only after the rear motor has been replaced - since the rear has to work before the footwell ones work.
5.) Opened up, cleaned and tested all fuses in the front fuse box. They all work.
So, once I replace the rear blower, I will probably be OK. But actually, I'm still having the problem of heat coming through the vents in the car even when the flaps are off and the motor is off. So I got under the car to see the heater valves. Both valves are open and then close fine when the levers are pulled up and then back down. So how can all this heat still be coming in through the car? Both heater valves have the openings to allow the heat out of the car, but I'm guessing there is also a door that needs to be closed? Is that door hidden from view? I guess I'll get back under the car and adjust those cables to maximum off. Actually, there is quite a bit of heat even with no heater motors or blowers, so I might not even have to replace the blowers in the winter!
08-17-2006, 04:34 PM
#6
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I don't think the switch in the middle (between the seats) do anything unless you have automatic controls for heat. The only fans are the footwells and the a/c blower located in the bonnet. The one one the motor stays at one speed (I think) to push air to the front and then pushed by your inside f/w fans. Do a search someone posted a very good picture of the controls and how they work not long ago. You have to pull down the flex duct to see the damper closer on the heater duct.
08-18-2006, 11:09 AM
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Bad information has been posted. The Automatic heat has the 10 speed heater control box mounted between the seats. The auto heat system has sensors, one in the cabin and one on a heater box. When the heater box air is hot enough it allows the system to operate. When the cabin temperature has reached its set point the cabin sensor turns off the system. Additionally there is a sensor mounted on the engine breather. If the car is stationary and the engine is running..and too hot, the sensor will turn the engine compartment fan on to move air thru the heat exchangers.
Ok, your problem...The 3 speed switch in the center console only controls the footwell blower speeds. If the red levers and flapper boxes are opening and closing then my first guess would be that the engine heat is being sucked into the cabin via the footwell blowers, but you state that none of the blowers operate?
The 3 speed footwell blower circuit is a bit odd. It requires that the rear blower be operational before it allows the footwells to operate. This logic circuit is located in the engine compartment controller. Positions one , two and sometimes zero on the center console direct power thru the switch contacts to the footwell blowers. Position 3 provides a ground path for the Aux relay. This relay directs power to the footwell blowers for high speed operation only. The reasoning behind this AUX relay is the high current draw of the motors. When operating at full speed they would over tax the micro switch contacts that are used on the slower fan speeds.
Another odd point is that some systems are set up so that even with the fan speeds set at zero the footwell blowers will spin at the same speed as position one. The reasoning for this change was to prevent the motors from overheating and blocking the air flow.
You can modify the engine compartment controller to allow the footwell blowers to operate without the rear blower. The info is in this thread..
http://forums.pelicanparts.com/showt...otwell+blowers
Ok, your problem...The 3 speed switch in the center console only controls the footwell blower speeds. If the red levers and flapper boxes are opening and closing then my first guess would be that the engine heat is being sucked into the cabin via the footwell blowers, but you state that none of the blowers operate?
The 3 speed footwell blower circuit is a bit odd. It requires that the rear blower be operational before it allows the footwells to operate. This logic circuit is located in the engine compartment controller. Positions one , two and sometimes zero on the center console direct power thru the switch contacts to the footwell blowers. Position 3 provides a ground path for the Aux relay. This relay directs power to the footwell blowers for high speed operation only. The reasoning behind this AUX relay is the high current draw of the motors. When operating at full speed they would over tax the micro switch contacts that are used on the slower fan speeds.
Another odd point is that some systems are set up so that even with the fan speeds set at zero the footwell blowers will spin at the same speed as position one. The reasoning for this change was to prevent the motors from overheating and blocking the air flow.
You can modify the engine compartment controller to allow the footwell blowers to operate without the rear blower. The info is in this thread..
http://forums.pelicanparts.com/showt...otwell+blowers
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08-18-2006, 01:35 PM
#8
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Since I'm already getting heat without any blowers working, I will just replace the engine blower - since it completely shot - and that should work for the winter. Porsche should have just gotten a bigger blower in back instead of implementing these footwell blowers in my opinion. I also have to start looking into the fresh-air blower, since that will also not come on. If the fresh-air blower is in the trunk, then where is the AC blower?
Last edited by Mike Murphy; 12-07-2006 at 04:09 PM.
08-18-2006, 04:49 PM
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The A/C blower is in the smugglers box, in the trunk between the firewall and fuel tank.
The rear heater blower on the early cars sucked and thats the reason they went with the additional footwell blowers. I backdated my exhaust and heating system when I switched to SSI heat exchangers. In doing so I removed the rear blower and installed the footwells in my 78SC. The system works better then it ever did.
I've been thinking about your problem. The flapper boxes have a damper inside them that blocks air flow into the car. When the damper is in the closed position the slotted vents are open and dump the hot air under the car. When the dampers are in open position the slots are closed and heated air is directed into the car. I'm betting that the internal dampers are not shutting all the way..or are rusted out. You need to get under the car and remove the flexible hose and have a peek inside the flapper box. Be advised that if they are badly rusted you need to be careful with them they might fall apart. Some WD-40 might loosen them up and put you back in business. You might also need to adjust the cables. Good Luck.
Oh, have you priced a new rear blower yet??
Rear Blower 965-624-151-00 $296
Left Footwell 911-624-043-02 $136
Right Footwell 911-624-044-02 $136
The rear heater blower on the early cars sucked and thats the reason they went with the additional footwell blowers. I backdated my exhaust and heating system when I switched to SSI heat exchangers. In doing so I removed the rear blower and installed the footwells in my 78SC. The system works better then it ever did.
I've been thinking about your problem. The flapper boxes have a damper inside them that blocks air flow into the car. When the damper is in the closed position the slotted vents are open and dump the hot air under the car. When the dampers are in open position the slots are closed and heated air is directed into the car. I'm betting that the internal dampers are not shutting all the way..or are rusted out. You need to get under the car and remove the flexible hose and have a peek inside the flapper box. Be advised that if they are badly rusted you need to be careful with them they might fall apart. Some WD-40 might loosen them up and put you back in business. You might also need to adjust the cables. Good Luck.
Oh, have you priced a new rear blower yet??
Rear Blower 965-624-151-00 $296
Left Footwell 911-624-043-02 $136
Right Footwell 911-624-044-02 $136
08-18-2006, 06:25 PM
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Yes, I know that new rear heater blower is expensive. I know there is a replacement for cheap, but I'll look for a used one on Ebay first (it's very easy to replace). You're right about the heater valves - they are rusted. But I think I need to adjust the cables and they should work well enough. I could also block off the heat airflow for the summer time. I just don't want to spend $150/valve and a new heater blower motor for $300 right this minute.
08-18-2006, 07:11 PM
#11
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My '87 has no automatic heat sensors (except for the engine overheat circuit mentioned above, but that directs the blower to run in reverse). Pulling up the red levers on the floor between the seats starts the engine compartment blower going, and once that one's on the auxiliary blowers will come on activated by the 3-position switch between the seats. My heater blower motor would not shut off even when the key was out and the culprit was the expensive rectangular relay in the engine compartment under a black cover near the coil. I was able to make sure by whacking it with my knuckle and the blower would shut off. My blower was also shot and after reading many posts here and in Pelican about ingenious cheap replacements that resulted in the auxiliary kickwell blowers no longer working apparently due to the resistance in the circuits no longer being just right, I decided to bite the bullet and get the OEM replacement. Hopefuly it will last another 18 years. Some folks have trouble with the red levers not shutting down the blower when lowered to the "off" position. It's not too hard to poke around in there and bend the contacts slightly to make sure the blower circuit is cleanly broken. If your rear blower is bad, and the front central fresh air blower has not been replaced, be prepared to replace that one. Mine started to creak about the time my rear blower needed replacing. Pulling apart the blower duct assembly and replacing that front motor can be daunting, but entirely possible with the Bentley manual and taking your time. So far, so good with my kickwell blowers. Lastly, if you ever do need to replace that blower relay, it's not available except through Porsche, and an excellent discounting dealer parts department is at Hennessey Porsche in Atlanta.
Still glad you chose the Red Pill?
I am.
Good Luck,
Dennis
Still glad you chose the Red Pill?
I am.
Good Luck,
Dennis
08-19-2006, 12:30 PM
#12
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Good advice, Dennis. I agree that replacing with OEM is the way to go, since it the blowers should last "another 18 years." By the way, what does everything think of Pelican? Are they reputable and carry OEM parts?
12-07-2006, 03:14 PM
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Update: I finally found someone selling a used rear engine compartment blower (an 8 on a scale of 1-10 for $65. I will install it next week, but my question is about the fuses by the footwell blowers. There are two non-porsche-style fuses, one on each side in-line with those footwell blowers. Should I even attempt to put new fuses in there and try out those footwell blowers? I just don't want to fry anything. If yes, where can I find those 10-amp fuses? These are not the same fuses as what's in the trunk or engine compartment, nor do they come with the spare fuse kit from VertexAuto or Pelican. Much thanks - and I can't wait for heat that doesn't require me to drive 80 mph!
12-07-2006, 10:19 PM
#15
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murphy, those 10 amp fuses are the new spade type used on all cars now. You can get them anywhere there is a parts store. I would go ahead and replace them to get the car back to a baseline just like it came from the factory. Someone stated the footwell blowers weren't needed, but on a trip recently I found my fuses had blown and the car wouldn't heat properly. Once I replaced the fuses, I could set my automatic heater control on 5 (out of possible 10) and it almost blew me out of the car.