I have a '91 190e 2.3L with a heating problem. After spending the last 2 days testing the various AC components, I determined that all the components worked and the reason the AC quit is that the amount of R-134 (it's been converted) was very low. Recharged the system (sort of, still a little low) and let the car run for awhile. Sitting in my garage at idle, the car heated up to 110C and keep climbing. Turned off the AC and took for a drive and got it back down to 85C. Turned the AC back on during the drive and the temp went to about 90C to 92C. 110C worries me. All aux. systems work. New water pump. Enough water in the tank.

My immediate thought is the thermostat which I will check tomorrow. Any thing else I should look into?

Andrew

 

andrew, your thermostat will start to open at 85-89 °C and fully open at 102 °C.

the viscous fan coupling will operate at 92 - 100 °C.

it makes sense that you are still on the tolerable operating temperature.

however, if you really feel it's quite high, just try to feel for some "cold spots" from different areas in your radiator.

do this after you shut off the engine at operating temp.

 

i also have owned a few 190e 2.3 in my day with the ac on they always ran a little on the warm side remember your car isnt overheating till it hits 120. 110 is a normal operating temp.

 

besides the thermostat (a cooler thermostat may be?) try this...

with engine not running and cold, use a garden hose spray water on the radiator from the inside (between the fan blades). This will clean a bit some accumulated dirt and bugs debris.

 

Thanks for all the replies. I haven't got to working on the AC again. While I was adding the rest of the R134 yesturday, the compressor started engaging, disengaging, engaging, disengaging, engaging, disengaging and so on until it disengaged completely and the idle shot way up (2500 rpm). Currently working on getting the idle back down. There seems to be a lot of post on this problem so there is lots of things to try. I am hoping that the compressor and the high idle are somehow linked (doubtful but hopeful). I'll let you know.

Andrew