heater problem
11-26-2003, 09:26 PM
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heater problem
I have a 1990 C2. When the A/C is turned on, the fan works fine until the temperature **** is turned higher than about 27 degrees. Above 27 degrees the fan will not work at all. It is possible to feel warm air if you put your hand up to the vents when the temperature is turned up. Any suggestions?
11-26-2003, 11:00 PM
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This is common. Check the fuse for the rear (or auxiliary) blower, you'll probably find it blown. The interior fan will cut out when heat is requested (higher temperature **** setting) if the rear blower is inoperable. You can replace the fuse, but if it blows again, you'll probably need a new rear blower (also common).
Good luck, and let us know what you find.
Good luck, and let us know what you find.
11-30-2003, 02:38 AM
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Hmmmm....Kinda' sorry to hear the fuse is good--that's the typical fix. Things will likely get more abstract from here.
The rear blower relay is the same relay that's used for the oil cooler & A/C condenser fans. These relays are in the fuse box in the trunk. Try swapping one of them with your rear blower relay (in the engine compartment fuse box).
Another thing you can check. With the ignition on, the rear blower should start running when the temperature is set to 27C or greater. If the rear (auxiliary) blower is not starting when you put the temperature at a high reading (say, red dot), you have a problem with the fan seizing, its power supply, or its CCU start signal. Since a seized fan would likely blow the fuse, your problem is probably with the power or start signal.
With the relay removed, you should find 12V at terminals #2 and 3 of the relay plug. This is "always hot" 12V. The rear blower is started in slow speed when the CCU completes the control circuit at #6, which repositions one of the two internal relays (one for fast, one for slow), connecting the 12V terminal #2 to terminal #7. More information on how this relay works can be found here, under "More Gory Details."
http://p-car.com/diy/fan/
Good luck, and let us know what you find.
The rear blower relay is the same relay that's used for the oil cooler & A/C condenser fans. These relays are in the fuse box in the trunk. Try swapping one of them with your rear blower relay (in the engine compartment fuse box).
Another thing you can check. With the ignition on, the rear blower should start running when the temperature is set to 27C or greater. If the rear (auxiliary) blower is not starting when you put the temperature at a high reading (say, red dot), you have a problem with the fan seizing, its power supply, or its CCU start signal. Since a seized fan would likely blow the fuse, your problem is probably with the power or start signal.
With the relay removed, you should find 12V at terminals #2 and 3 of the relay plug. This is "always hot" 12V. The rear blower is started in slow speed when the CCU completes the control circuit at #6, which repositions one of the two internal relays (one for fast, one for slow), connecting the 12V terminal #2 to terminal #7. More information on how this relay works can be found here, under "More Gory Details."
http://p-car.com/diy/fan/
Good luck, and let us know what you find.
11-30-2003, 02:45 AM
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Oh yeah. One more thought. Your slow speed resistor for the rear blower could be failed. With the relay removed, you should get ~350 ohms between terminals #5 & #7. If you get some super high value, you've found your problem.
12-01-2003, 04:38 PM
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So last night I took the relay out and have attached the pictures here if all went according to plan.
http://forums.rennlist.com/upload/relaysocket1.jpg
http://forums.rennlist.com/upload/relaycontact1.jpg
I was hesitant to switch out the relay since I don't have a spare. I'm not sure, but does it look to anyone else like there's some damage done? Is there any other source drawing current from that relay? If you could see the other side of the contact not visible in the contact picture, the copper is almost all burned off and there is mostly the white surface visible.
The other thing is, I don't know how long it will last, but after fooling with the relay and a few gentle "taps" on the table before reinstalling the relay, the rear blower is working again for now. There is heat and appropriate temperature at all levels. Would you think there is any reason to keep searching for another problem? I'm just not clear on why that relay would blow like that as an isolated problem. Any ideas?
Thanks.....
http://forums.rennlist.com/upload/relaysocket1.jpg
http://forums.rennlist.com/upload/relaycontact1.jpg
I was hesitant to switch out the relay since I don't have a spare. I'm not sure, but does it look to anyone else like there's some damage done? Is there any other source drawing current from that relay? If you could see the other side of the contact not visible in the contact picture, the copper is almost all burned off and there is mostly the white surface visible.
The other thing is, I don't know how long it will last, but after fooling with the relay and a few gentle "taps" on the table before reinstalling the relay, the rear blower is working again for now. There is heat and appropriate temperature at all levels. Would you think there is any reason to keep searching for another problem? I'm just not clear on why that relay would blow like that as an isolated problem. Any ideas?
Thanks.....
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12-01-2003, 05:05 PM
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Wow, that doesn't look pretty. 
I would check the amperage of the fuse installed for the rear blower. It's possible a previous owner had problems with it blowing in the past, due to the motor binding, and made a band-aid fix by upping the fuse rating. Which in turn could cause the relay to overheat.
Or, perhaps someone shorted the output while trying to test the rear blower, though that seems unlikely.
Can you tell if the burning is on the control pins/terminals or the power pins/terminals? Control = #1, #6, #8 on the plug, #85, 85c & 86 on relay. Power = #2, #3, #5 & #7 on the plug, #30c, 30 87 & 87c on the relay. I can read #8 in your picture (which isn't burned), but I can't read any of the other plug numbers.
There are no other components powered by the relay.
If you're not using your A/C, you can throw the A/C condenser relay in for the time being, until your new relay arrives.
Well, the good news is, you now know the source of your problem. At worst, I think you'll need to replace the rear blower, if it blows fuses (of the proper rating
).
Please keep us posted on how things turn out.
I would check the amperage of the fuse installed for the rear blower. It's possible a previous owner had problems with it blowing in the past, due to the motor binding, and made a band-aid fix by upping the fuse rating. Which in turn could cause the relay to overheat.
Or, perhaps someone shorted the output while trying to test the rear blower, though that seems unlikely.
Can you tell if the burning is on the control pins/terminals or the power pins/terminals? Control = #1, #6, #8 on the plug, #85, 85c & 86 on relay. Power = #2, #3, #5 & #7 on the plug, #30c, 30 87 & 87c on the relay. I can read #8 in your picture (which isn't burned), but I can't read any of the other plug numbers.
There are no other components powered by the relay.
If you're not using your A/C, you can throw the A/C condenser relay in for the time being, until your new relay arrives.
Well, the good news is, you now know the source of your problem. At worst, I think you'll need to replace the rear blower, if it blows fuses (of the proper rating
). Please keep us posted on how things turn out.
12-02-2003, 08:59 PM
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The fuse is a standard 30 amp fuse so it doesn't appear that there was any tampering done there. As an aside, what did you mean about motor binding causing problems?
It looks like power terminal #5 took one for the team. It's the most burned out in appearance although it's hard to compare the amount of damage done on the dark metal of the relay. But on the relay, there is a gold plated(?) disc next to pin #87 that looks to have a substantial amount of wear. The other similar discs adjacent to pins 30c and 87c don't look bad. The one contact is bad on the inside of the relay as you can tell.
Do you know if the relay is an S relay or K-shaped relay? I've heard there are differences in how long they last.
I think I see where you were going with the question about which pins or terminals are burned the most. Is there a tamping diode in the relay? But even if so, I looked and there is only one way to plug it in so I don' t think someone shorted a wire that way.
I saw on Pelican parts that their relays are about $40. Does that sound about right?
It looks like power terminal #5 took one for the team. It's the most burned out in appearance although it's hard to compare the amount of damage done on the dark metal of the relay. But on the relay, there is a gold plated(?) disc next to pin #87 that looks to have a substantial amount of wear. The other similar discs adjacent to pins 30c and 87c don't look bad. The one contact is bad on the inside of the relay as you can tell.
Do you know if the relay is an S relay or K-shaped relay? I've heard there are differences in how long they last.
I think I see where you were going with the question about which pins or terminals are burned the most. Is there a tamping diode in the relay? But even if so, I looked and there is only one way to plug it in so I don' t think someone shorted a wire that way.
I saw on Pelican parts that their relays are about $40. Does that sound about right?
12-03-2003, 06:01 PM
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>The fuse is a standard 30 amp fuse so it doesn't appear that there was any tampering done there. As an aside, what did you mean about motor binding causing problems?
The fan can wear out and seize. Which in turn causes the fuse to blow. Replacing the rear blower because of it blowing fuses is, unfortunately, fairly common.
>It looks like power terminal #5 took one for the team. It's the most burned out in appearance although it's hard to compare the amount of damage done on the dark metal of the relay.
#5 is the power supply for fast-speed operation (relay-out). #7 is for slow-speed (relay-out), where slow-speed is created by a 0.450 ohm ballast resistor between the 12V power and the motor. It makes sense that #5 is where the damage is, considering that it's where the current will be highest (no in-series resistor to lower current).
>But on the relay, there is a gold plated(?) disc next to pin #87 that looks to have a substantial amount of wear.
Yep, #87 matches up with #5.
>The other similar discs adjacent to pins 30c and 87c don't look bad.
30c is the relay goes-in power for slow-speed. 87c is the relay goes-out power for slow-speed.
>The one contact is bad on the inside of the relay as you can tell. Do you know if the relay is an S relay or K-shaped relay? I've heard there are differences in how long they last.
Nope, sorry, don't know.
>I think I see where you were going with the question about which pins or terminals are burned the most.
I was looking to verify that the over-current condition was occurring in the most likely location, which it is.
>Is there a tamping diode in the relay?
Don't know, I haven't dissected one yet. I only know which pin does what, and that there are two internal relays.
>But even if so, I looked and there is only one way to plug it in so I don' t think someone shorted a wire that way.
>I saw on Pelican parts that their relays are about $40. Does that sound about right?
Roy Eames reported here a year or two ago that the relay is “generic” (Volkswagon, Audi?), and can be purchased from Pelican Parts for $15.80. When I bought one, I got it from Sunset Porsche (dealer cost +15%) = $28.00.
Recapping the relay pin/plug functions:
#1 on plug/85 on relay = control "signal" for fast-speed.
#2 on plug/30c on relay = goes-in 12V power for slow-speed.
#3 on plug/30 on relay = goes-in 12V power for fast-speed.
#4 = not used.
#5 on plug/87 on relay = goes-out 12V power for fast-speed.
#6 on plug/85c on relay = control "signal" for slow-speed.
#7 on plug/87c on relay = goes-out 12V power for slow-speed.
#8 on plug/86 on relay = control power.
Hope this helps. I think you have the problem under control.
The fan can wear out and seize. Which in turn causes the fuse to blow. Replacing the rear blower because of it blowing fuses is, unfortunately, fairly common.
>It looks like power terminal #5 took one for the team. It's the most burned out in appearance although it's hard to compare the amount of damage done on the dark metal of the relay.
#5 is the power supply for fast-speed operation (relay-out). #7 is for slow-speed (relay-out), where slow-speed is created by a 0.450 ohm ballast resistor between the 12V power and the motor. It makes sense that #5 is where the damage is, considering that it's where the current will be highest (no in-series resistor to lower current).
>But on the relay, there is a gold plated(?) disc next to pin #87 that looks to have a substantial amount of wear.
Yep, #87 matches up with #5.
>The other similar discs adjacent to pins 30c and 87c don't look bad.
30c is the relay goes-in power for slow-speed. 87c is the relay goes-out power for slow-speed.
>The one contact is bad on the inside of the relay as you can tell. Do you know if the relay is an S relay or K-shaped relay? I've heard there are differences in how long they last.
Nope, sorry, don't know.
>I think I see where you were going with the question about which pins or terminals are burned the most.
I was looking to verify that the over-current condition was occurring in the most likely location, which it is.
>Is there a tamping diode in the relay?
Don't know, I haven't dissected one yet. I only know which pin does what, and that there are two internal relays.
>But even if so, I looked and there is only one way to plug it in so I don' t think someone shorted a wire that way.
>I saw on Pelican parts that their relays are about $40. Does that sound about right?
Roy Eames reported here a year or two ago that the relay is “generic” (Volkswagon, Audi?), and can be purchased from Pelican Parts for $15.80. When I bought one, I got it from Sunset Porsche (dealer cost +15%) = $28.00.
Recapping the relay pin/plug functions:
#1 on plug/85 on relay = control "signal" for fast-speed.
#2 on plug/30c on relay = goes-in 12V power for slow-speed.
#3 on plug/30 on relay = goes-in 12V power for fast-speed.
#4 = not used.
#5 on plug/87 on relay = goes-out 12V power for fast-speed.
#6 on plug/85c on relay = control "signal" for slow-speed.
#7 on plug/87c on relay = goes-out 12V power for slow-speed.
#8 on plug/86 on relay = control power.
Hope this helps. I think you have the problem under control.
Last edited by Randall G.; 12-04-2003 at 10:06 AM.
