coolant temp. sensor
 

I have a 93 300se, model 140. If the coolant sensor is faulty, does this effect the blower motor going on and the compressor going on and off? my blower motor has been working on and off for some time now. today my auxillary fans were on full force, and the temp. outside was 25 degrees. I tapped the Temp. housing and my blower motor and compresser came to life. I then played with the black plastic connector to the sensor and the compressor would come on and off. Does this sensor effect these components. How can I check to see if the sensor is good or not, before I order a new one?

I have seen the instruction once before
 

I believe if your coolant sensor is the round type (one with 4 pins) you need to check the resistance across each or the two opposite pins (for example if you draw a diamond shape with each pin represents each corner, then you'd want to test the two opposite pins and not the adjacent ones). The resistance should vary depending on the engine (coolant) temperature. So you first check when engine is cold, then check when you start the engine and coolant starts warming up etc.. each time write down your measurements (for both sets of pins). If you see the resistance values don’t change, then the sensor is bad. from what you described above, you either have a bad sensor or bad wiring/connector that plugs to the sensor. I'd change the sensor anyway since it's only about $15 or so. Good Luck and let us know what you come up with.