jnsluft

After losing all temperature control, I checked the codes on the climate control display and it read 8.5. I found the Tech Article from Living Dissed, and used it to disassemble the dash. I removed the temperature control servo, cleanded the motor and relubed it. After replacing the servo, it still doesn't move. Checing codes again, it now reads 8.3 and 8.7. After going through the work to remove it, I don't want to do it again. Should I be checking anything else? I do have cold A/C, defroster control, and adjustable fan speed. Everything works except for being able to control the temperature.

If I replace the servo with a new one, will the codes disappear on their own, or will they have to be cleared.

Thanks,
Shawn

dorsal900

Please tell me what codes 8.5, 8.3 and 8.7 translate to, or provide a link to the list of codes from the CC head. I would like to help you, please make it easier to do so.

jnsluft

The codes are:
8.3 Temp regulator flap motor potentiometer, sporatic open
8.5 Temp regulator flap, static block
8.7 Temp regulator flap, sporatic block

I'm thinking I'll just replace the servo. But will the codes clear themselves when the new unit is installed, or will I need to buy a VAG-COM scan tool?

Shawn

dorsal900

OK, thanks for the decoding - I use a VAG-COM, which gives different numbers for the same codes.

It sounds like the temp regulator flap solenoid has improved from a "static block" to a "sporatic block". A couple of questions on how you cleaned the solenoid:
1. Did you also clean out the potententiometer when you had the motor opened up, i.e. sprayed some contact cleaner inside and wiped it around vigorously? These also get gummed up and are the source of erroneous readings by the HVAC control unit.
2. After cleaning, did you try the motor out of the car, exercising it in both directions with a 7V source? Did it run smoothly, no binding?

I cleaned the temp regulator flap solenoid in my car this way, and it did fix the problem. Also note, that I did not remove the center console to get to the solenoid, only the glove box and the right-side panel of the center console; I wrote this up for the B5 FAQ section, which is now impossible to find.

I have a feeling that a new solenoid will self adapt, as the solenoids seem to run when the car is first started - but I could be wrong...........

jnsluft

I only cleaned the motor. I didn't do anything else in the unit. I'll go back in and look it over some more. It can't hurt.

dorsal900

OK, it's a pain to keep doing this, and someone here wrote that they improved the solenoids on replacement parts, but perhaps not for the older models like we have - and this is only a rumor until I see it myself. Sure, a new $100+ part will fix the probem, but what fun is that?

When I took apart the solenoid, I carefully measured the resistance on the potentiometer as it swept through its range of motion. This produced non-linear results, i.e. higher resistance midway through the range than on either side of this point, meaning that it was dirty/corroded and would be providing bad information to the HVAC control unit. I imagine that the temp control flap spends a lot of time in the center of its range of motion, a location that produces 72-degree air. After a good cleaning, it was much better, no high-resistance spots along the movement.

I am in the electronics business and tried to find a replacement potentiometer (should cost <$1), but couldn't find anything that would fit in the tight configuration with the shaft coming in from below the circuit board; after I got it working properly, I forgot about it. It's now been working for a year, so I'm leaving it alone.

jnsluft

I'm only considering the new replacement part because of the amount of work it would take to remove it again.

I've been pretty fortunate cost wise with my other repairs, so $130 for a new servo doesn't upset me.

Shawn

dorsal900

I certainly understand, and if I wasn't in electronics (thereby understanding what a potentiometer should cost), I would probably have done the same thing!!!

jnsluft

I tried cleaning the pot two more times today. No luck. Still shows 8.3 and 8.5. I guess it's time for a new servo. Thanks for everyone's help.

Shawn

dorsal900

Oh well, things do break beyond repair.