MBGOULART

I am trying to diagnose a non-functional A/C system and continuously running auxilliary cooling fans on my 190E-2.6. I believe that these problems are related. If so, the most likely faulty component is the coolant temperature switch (identified as S25/5 on my model). This switch starts the aux fans when coolant temp reaches 105C and cuts-out the a/c compressor when coolant temp reaches 115C.

I believe the this switch may be "stuck" closed. I researched and reviewed the aux fan circuit and identified and tested the pre-resistor relay and aux fan relay, and their circuit interfaces. All appear to be operating fine.

NOW THE BIG QUESTION. I can't locate the temp switch. According to my OEM manual, it is supposed to be located at the top, front of the engine. There is a photo of the location in my manual, but it shows the location on the 2.3-16, not the 2.6 (same switch for both). I assumed the switch was located on the water pump, but I can't see anything that looks like a switch. ANYBODY KNOW WHERE THIS DAMN THING IS????

YNVDIZW124

Since i have a 300e ima help you out! It's the green one by the cold start valve with the 3 connections!

crissycut

Yes, I think that's the case because when you connect the 2 wires on the temp switch, fans will turn ON so it might be grounded.

SRDiver

and check your fuses - a bad fuse from the heating curcuit will also turn on the fans.

SRDiver

and on the 2.6 the sensors are found along the block between where the intake manifolds attach

MBGOULART

Thanks to everyone, especially YNVDIZW124. Your initial response helped me locate the sensor. I found that the sensor is bad. Both the Aux fans and A/C compressor switches are shorted to ground, which keeps the fans running and disables the A/C compressor.

Now my next question; the sensor has wrench flats, but they are almost impossible to reach with the fuel lines in the way. Anyone have suggestions on how to get this unit out with commom mechanics tools?