W123 Climate Control Problem - full hot or full cold, no middle ground

[kyle242gt]

Hi all -

I have an 84 300D, 215K on it.

The problem: any setting above MIN on the ACC temp dial has hot air coming out.

I have run through the troubleshooting on the CD to the best of my ability. All switches, vacuum units, fan, aux pump, temp sensors, checked out. Monovalve has a new kit in it.

I disassembled the temp dial, cleaned the traces, reassembled - no change.

I'm considering adding a potentiometer to the ambient temp sensor, thinking maybe, just maybe, the ACC control unit thinks the car is colder than it really is.

I've posted about this on the BW forums in the past, but haven't gotten any help.

Crazy thought - is it practical to retrofit a non-ACC control unit? I find myself thinking if I could just rig a cable to the temp dial and put a normal manual water valve in, I'd be all set.

Thanks for any advice!

[lakerat]

My cars is doing the same thing I have resoldered the push button control unit , replaced mono valve with kit , tested mono valve it turns off when it is suppose to per climate control manual, but all it does is full hot or cold. I have replaced the foam hose for the in car sensor, could it be the climate control unit? Thanks for any help

[kyle242gt]

I have never gotten anywhere with this, ever. In addition to the problems in the OP, the fan will set its own speed, even if the low speed override button is pressed.

Pretty much everyone accepts that W123 climate controls are junk.

I only drive it ten minutes at a stretch, so I just live with it.

If you come up with something, please do post!!

Have you tried replacing the pushbutton unit?

[kyle242gt]

I have not. Haven't been to the JY to track one down, though I have inquired in "parting out" threads to no avail.

Anyone have a known-good unit?

[mlozzi200478]

ive had issues also,no matter what button i push air comes out of all vents heater,defrost,side vents,except the 2 middle vents of course they need to be set to e/c on a/c. but,have you checked the temp sensor on the ceiling above the rear view mirror,or checked to make sure the return fan behind the passengers vent is working correctly it monitors the air temp of the automatic climate control.good luck