Thanks to one and all here for a great forum...
I just bought my 96 E-320 (73K Miles). Car came from Canada origianlly. First thing I did was take it in to the non Mercedes dealer Mercedes car people here in Birmingham Al. to go over it and fluid changes (I live in an apartment complex so dont really have a place to do it myself). During the service the belt needed replacement and we found slack in the water pump shaft...although there were no coolant/seal leaks, I elected to replace the pump. In process of all of this the question of temp and cooling fans came up. The temp (gauge in Centigrade) would run around 80 C on the road... in traffic would go up to around 105-110 C with the air conditioner on. Replaced the 85C thermostat with a 75 C thermostat (further south than Canada) at the recommendation of the shop. Question is since this is a Canadian car, should the cooling fan circuit be reset to come on at a lower temp?? Cooling fans come on around 110 C. I was concerned that maybe there was something wrong with the fans and/or circuit controlling the fans (they dont run all the time with the air conditioner on). The shop could not find schematics covering the 4 wire temp sensor that screws into the thermostat gallery on the top of the water pump. Also the fan appears to be variable speed using pulsating DC to control the speed. Additionally the screw in sensor unit appears to be a pair of thermistors rather than switches (I measured the resistance with an ohmmeter)
Since we cant find any literature on this (I would guess since the E is Canadian and different in some ways from the ones imported into the US) Id really appreciate thoughts on the whole cooling fan thing-- where should they switch on and/or off and is this settable?? If so should they be set to switch on at a lower temp(further south and much warmer summers). Is my supposition that the screw in sensor is in fact thermistors??
Thanks to all here for a great place for technical info !

Carr McCormack
Birmingham Al

The fan clutch should lock the engine driven fan by around 100C. The electric aux fans located in front of the radiator should cycle on and off with the air conditioner when the pressure gets too high. They only go on high speed when the engine reaches a temp of 110C or so according to US specs. I also believe the stock temp of thermostat is around 87C in the US. Your temp sounds about normal.

The auxillary fans are famous for failing on this.

I have replaced a clogged radiator or two.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

Donnie,
I noticed your 300D. Did you just acquired it? I think you were talking about getting it...How do you like it?

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J.H.
'86 300E