QuestionQUESTION: What temperature does the auxiliary fan come on to cool the engine? I no longer hear the fan come on after driving in stop go situations and it used to come on when I parked the car or before I parked it. The temperature gage is showing 100 degrees and no fan is coming on. Mechanic has changed fuses and switches to no avail.
ANSWER: Hello Tezzy,
I would check the fan blades to see if they rotate easily. ( do this when the engine is cold). If the blades turn easily, then you know the shaft bearing are OK.
In warm weather, the fan should operate full time when the AC is on. And should cycle to keep the temperature below 100C.
I would suspect that the temperature thermo-switch may be defective. It is located near the water inlet on top of the engine. If it is not closing when the water temp goes above the set point then the fan will not come on .
Additionally there is circuit in the AC that should engage the aux fan any time the AC is on High.
The EC (economy mode) circuit may be keeping the AC from engaging to allow the engine to get better fuel mileage.
Hope this helps.
Rob
---------- FOLLOW-UP ----------
QUESTION: Hi Rob,
The temperature is now able to drop down when the car is acclerating and the mechanic says the issue is fixed with the auxiliary fan. However, I still do not hear what he identified as an "after-run fan" that would come on when I park the car. Mechanic says he wasn't aware of the '88 Mercedes using this part back then. However, I could swear that I used to hear it and no longer do. Is there a such part for this model and year? And is that a whole seperate issue? Is it a critical item?
Thanks,
Tez
AnswerTezzy,
The electric fans use a separate circuit to determine when they operate. It is not automatic that the fan would operate after shutting of the car, unless the radiator temperature is excessive.
Coolant temperature tends to rise after the engine is stopped because all the engine block heat is being absorbed by the coolant. It the block thermal switch senses a possible boil over, the fans will continue to operate after switch shutdown to bring the coolant back into the safe range.
So, if your vehicle operating temperature is not out of the save range, the fan may not engage.
When operating the AC, however I would think that the electric fan(s)should operate full time to keep the coolant in range because of the added load of having to remove heat from the interior of the car.
Hope this helps.
Rob
