Dr Mitch

I've done some reading on Rennlist and Tore's site.
At one point the drivers side (LHD) vent would only blow hot air. The servo mixing flap wouldn't move, took it apart and cleaned, nothing, so I just set it in summer so the flap was closed. Well it started working properly again! But, occasionally I get hot air only through the drivers side vent with AC on and set to coldest position (other vents blow cold air).
I have checked and the flaps still work properly.
Guessing one of the other driver side servos is malfunctioning. Any suggestions on where to start?
(I had the leaky hot air tube that I mended already).
Seems to occur when I turn on and off the a/c.
Middle and passenger vents still get cool air (not very cold AC which I think is another issue...).

A8KED

Like you I had mixing servos that would not move. I opened them up and cleaned the contact points with alcohol and reassembled them. My cleaning worked and the servos started moving again. But when I reassembled one of them I reinstalled the movement arm in the wrong position and the servo would only move part way. Maybe you have a similar issue?

tbennett017

Also the circuit board on the servo will burn in one spot, but if you reassemble it in a different orientation, the motor will work until it hits the same burnt spot again, where it fails at the same location. This way they have a tendency to go back to the same place and fail over and over.

Rocket Rob

There are 5 servos in the HVAC system. The left and right side mixing servos get the most use and tend to wear out first. I would use Tore's troubleshooting guide to determine if its time to replace yours.

Spyerx

Servos are:
Left heat mix
Right heat mix
Recirculate
Floor vent
Defrost vent

Just replace the servo. Before installing it plug it in and let it cycle to the correct spot make sure all settings on ccu are cold, defrost off, sliders to the left. The door is closed on the heat mix servo at cold which is the collapsed setting on the rod. It extends to open.

urquattro20Vt

After dealing with flaky servos for a couple years I had them fixed - see my thread here:
https://rennlist.com/forums/964-foru...-repaired.html

He replaces the PCB board and motor with new parts. Talking to an EE friend of mine who I had look at mine - he said getting a batch of new PCB boards made would be easy - I'm guessing that's what Micheal did.

Strongly recommend.

Spyerx

Link to shop or store? If it's guy I'm thinking of prices went up and you can get new ones for nearly same price.

Rocket Rob

Link = http://www.partisan-autoteile.de/epa...le_fuer_964993

Spyerx

Ok different store thanks for link. With crappy euro value it's cheaper. New servos are in the 350 range shipped from sunset.

Dr Mitch

Thanks!
When I change temp **** from hot to cold, both servos move and close the vent, but still getting hot air - especially when at highway speeds, a/c doesn't change it at all now - the faster I go, the hotter it gets! Wondering if one of the flaps is getting stuck open?
Will take it to the shop - depending on what they find, may send all of the servis off to Partisan for repairs.

Spyerx

Check the flapper boxes in rear of car. They need to move when the airbox vents are closed the rear hit air vents into the rear wells. When you open the heat up in front the flapper boxes in rear open and direct air to the front.

If these things don't move freely (there is no motor it's based on airflow) they could lock forcing air to the front.

So, check and make sure servos are fully closing the air box on left and right and then check the flappers in the rear of the car.