Air on electrical problem S212

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Metalmickey321

New Member
Joined
Oct 23, 2021
Messages
19
Location
Chesterfield
Car
E220
Hi

on Saturday we had a trip to the coast in 2012 E220 estate. The aircon was working a treat; as always. When we returned to the car immediately from start up, the air on was blowing at high temp to the windscreen. it was set at low on both sides and blowing to face level vents. I could adjust the fan speed but flow direction or temp.

I plugged in my code reader tonight and got 2 active codes in the aircon.
I got codes: 00800 & 9ED187
D00800 says LIN bus 1 has a malfunction.
9ED187 says Humidity/temperature sensor has a malfunction. The message is missing.

I have access to a parts car and have swapped the heater control module; which made no difference. Next I swapped the humidity/temp sensor behind the rear view mirror and both sensors in the front footwell kick plates.

After swapping all these, the aircon works as it should for between 5 & 10 seconds then goes back to blowing hot air at the windscreen again. It won’t adjust temp, or direction. but if I switch off and leave it for a few mins I can repeat the cycle of aircon working for about 5 to 10 seconds and back to hot air only at the windscreen.


The aircon pressure is running at give or take 190 psi and the refrigerant is good as I had it fully gassed last summer and it does work briefly.

Any suggestions as to what else could be wrong? It would seem electrical / sensor related but I’m stumped at what to try next.

Please help!
 
What does the outside temperature reading in the instrument cluster say? I’ve seen faulty outside air temperature sensor cause unusual climate control behavior before
 
What does the outside temperature reading in the instrument cluster say? I’ve seen faulty outside air temperature sensor cause unusual climate control behavior before
On Saturday when the problem first happened it was reading 23.5C. Yesterday morning it was reading 17.5C. I didn’t check today. I’ll keep an eye on it tomorrow and update. I’ll also see what temps my reader is saying for different sensors.
 

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