Erratic Climate Control Potentiometer
 

The Climate Control Potentiometer on our 87 560SEL shows resistance from one extreme of 2.1 KOhms, rising immediately on a very small turn to 6 KOhms and, turning a little further, dropping to ~ 4 KOhms and staying there till the other extreme where it drops completely to 11 Ohms.

The vacuum system and other sensors check OK. The solder joints in the circuit board seem solid. We tried both contact cleaner and WD-40 on the potentiometer (which seems quite sealed) with no change at all.

The problem I'm trying to fix is fluctuation every few minutes from extreme cold to extreme hot with high fan coming on at both extremes. This occurs no matter where the control is set.

We have checked and cleaned the inside air sensor and sampler motor and tubing and it performs as the shop manual says it should, holding a small piece of paper up against the vent till the ignition key is turned off, when the paper immediately drops.

Are we on the right track?

Does anyone know where I can buy the correct potentiometer without having to buy the whole unit, as I did last time?

Go to Radio Shack and get sone 'Tuner Cleaner' or 'switch and contact cleaner'. Shoot some into the innards of the pot and move the dial around. The problem is that dust causes problems inside the inner workings. It's like the noisy volume control on your stereo. (The older ones not the newer ones with the volume up/down buttons).