Hi Guy's, This is my first post, So I hope that I do it right, Here goes. I am an Auto-Electrician and I am working on a Mercedes C250 Turbo diesel 1998 model 202,128, It came in for the aircon not working, It needed Gassing so that has been done by the garage that sent it in to us, The aircon compressor would not pull in, so after qiute a bit of testing we decided to change the control panel, The Aircon now works and gets the temperature down to about 4 degrees celsius, so it appears that it is working ok. Now the only problem is that the compressor will only pull in when the engine temperature rises to about 80 degrees celsius, and if you drive the car from cold it struggles to get up to 80 degrees, if it is then left ticking over for a while, it gets up to 80 + and then you can drive it and the temperature stay's up and the aircon works fine, My Questions are:- should the aircon on this model only work when the engine warms up or should it work as soon as the engine is started, (I have ordered a new thermostat, to see if I can get the engine to warm up quicker).

The A/C system is designed to operate ANY time that you request so!

There are many temperature imputs to the control unit, one of those imputs must be causing that problem. That system can be scanned for problems with correct diagnostic tool.

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Hi. MB Doc. Thanks for your reply, That is what we expected, (for the air con to work at any time). But this one has got us beat, after fitting a new thermostat, the engine now warms up whilst driving which it struggled to do before, and the aircon works as soon as it gets to about 75 degrees, I was checking it using a Bosch kts 650 which would not give live data, and a snapon scanner which gives live data but the temperatures seem to be wrong. ( tested on 2 different Mercs) . no fault codes listed in either air con or engine management. We also wondered if it was designed not to work from cold start as the glow plugs could still be on, and if the aircon was turned on at the same time it could possibly cause the car to struggle to pull away from juncyions etc. (we have had a few customers with various cars complain that if the aircon is tuned on the car struggles to pull away). ??