A/C Center Vent / Controller Problems
06-27-2001, 12:15 AM
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A/C Center Vent / Controller Problems
Hoping somebody can help with an a/c controller question. Here's the story so far:
1980 Euro S with automatic climate control
A/C controller would output low voltage (3.5v) on "auto" and "bi level", but would output 12v on "defrost".
Today I pulled the controller, fully expecting to see a burned out relay... but found that the relay was in pristine condition. What I discovered instead was that several contacts on the selector (eco/auto/bi-level/defrost) lever were bent up and hence not making good contact with the traces below them. I cleaned the traces with some acetone, bent the contacts out (gently!), and put the assembly back together. Installed it, turned on the A/C, and Voila! However, I noticed a few problems:
1. Controller has output voltage when switched to "eco". I measured it at 5v. As "eco" allegedly means "vent/heat only", shouldn't there be zero measurable output voltage? Also noted, the a/c clutch is trying to engage but slipping (as one would expect with this voltage being applied), resulting in the compressor turning but very slowly. I'm guessing this can't be good for the clutch, hence I am not using the "eco" setting presently.
2. Center vent closes as soon as you turn on the a/c. When set to "eco", the vent opens fully... but as soon as you switch to auto, bi-level, or defrost, the vent closes. According to the owner's manual, it should close on Defrost, and should otherwise close only if coolant temp falls below 130 degrees or something like that... but in this case, it stays closed all the time... (took it out for a little drive, warmed up the engine to the middle third of the temp gauge, still no center vent. Is there a temp sensor that could be bad here? Any ideas as to what this could be?
3. This is related to the first question. Measured the output voltage of the controller at the freeze switch with the controller set to 'auto'. Pegged 15v on my meter. I'm guessing voltage is around 17 volts or so... is this a problem? Obviously, it's working to activate the compressor clutch, but could the high voltage be an indicator of something else dodgy in the controller?
Thanks for any advice/replies, and feel free to email me with any specifics!!
-Brian Bowman
'80 Euro S 5sp
Member, 928 Owners Club
1980 Euro S with automatic climate control
A/C controller would output low voltage (3.5v) on "auto" and "bi level", but would output 12v on "defrost".
Today I pulled the controller, fully expecting to see a burned out relay... but found that the relay was in pristine condition. What I discovered instead was that several contacts on the selector (eco/auto/bi-level/defrost) lever were bent up and hence not making good contact with the traces below them. I cleaned the traces with some acetone, bent the contacts out (gently!), and put the assembly back together. Installed it, turned on the A/C, and Voila! However, I noticed a few problems:
1. Controller has output voltage when switched to "eco". I measured it at 5v. As "eco" allegedly means "vent/heat only", shouldn't there be zero measurable output voltage? Also noted, the a/c clutch is trying to engage but slipping (as one would expect with this voltage being applied), resulting in the compressor turning but very slowly. I'm guessing this can't be good for the clutch, hence I am not using the "eco" setting presently.
2. Center vent closes as soon as you turn on the a/c. When set to "eco", the vent opens fully... but as soon as you switch to auto, bi-level, or defrost, the vent closes. According to the owner's manual, it should close on Defrost, and should otherwise close only if coolant temp falls below 130 degrees or something like that... but in this case, it stays closed all the time... (took it out for a little drive, warmed up the engine to the middle third of the temp gauge, still no center vent. Is there a temp sensor that could be bad here? Any ideas as to what this could be?
3. This is related to the first question. Measured the output voltage of the controller at the freeze switch with the controller set to 'auto'. Pegged 15v on my meter. I'm guessing voltage is around 17 volts or so... is this a problem? Obviously, it's working to activate the compressor clutch, but could the high voltage be an indicator of something else dodgy in the controller?
Thanks for any advice/replies, and feel free to email me with any specifics!!
-Brian Bowman
'80 Euro S 5sp
Member, 928 Owners Club
