Need Normal Temp Gauge Reading- 99 E300 TD

Normal engine temp is 85, plus or minus 5, higher under load and lower if outside is very cold. The aux fans kick in between 100 and 110, depending on year/model and engine, or when A/C is running.

RE: AC and Aux fans

Not sure about this model, but in many older MB's, eg 116, the aux fan does not automatically come on with the AC. The temp at the receiver/dryer has to be above a certain temp, which is pretty hot, so it only comes on if it's a very hot day.

On my W201 and W126, the A/C pressure turns on the aux fan. Unless the refrigrant is very low, the aux fan is on within a minute after compressor runs. I have another W202 but I am not sure how it runs.

All late models have many computers > Wan-n>

Thank you both for the information. I feel much better now that I know that my temp reading is the norm.

This discussion gave me an idea. I have a 116 that was converted to R134 some years ago. With the conversion, you lose some cooling capacity, maybe 20=25%. So, I'm thinking if I bypass the temp switch on the receiver/dryer, the aux fan will always go on with the AC. That should help lower the outgoing refrigerant and provide some additional cooling capacity on days when it's not quite hot enough for the fan to go on via the temp switch.

AT any rate, I don't see any downside.

Well there is a downside... it is so noisy! Check the charge... it is usually the charge that affect the cooling capacity. On R134a... it should be around 30 PSI when running.