Testing an Engine Temp Sender?
 

I'm not getting any temp reading in the dash on my 1975 450SL. All other gauges work and all fuses look good. Car starts cold fine, idles down off of cold idle, etc. But no reading on the gauge.

Is there anyway to test the sending unit (rear in right head) w/o blindly changing it?

Any tests I can do @ the back of the gauge to see if something in btw is the cause?

Other suggestions about what might be the cause?

Thanks!!

Coolant temp sensor should have single GREEN wire..NTC sensor

OHM readings should be 110 at 60C...67 at 80C...& 38 at 100C

Sending Unit or Gauge??
 

Hey all,

'75 450SL w/ a dead temp gauge:

Is there any way to test whether the gauge is faulty or if it's the sending unit?

Thanks!

Ohm the sensor unit

OHM 110 = 60C
67 = 80C
38 = 100C

I have a 38 ohm /1% tol. resistor in my tool box that I sub in place of the sender unit.. this will tell if the gauge or sender is the fault without having to warm the coolant/run the engine to the different temps......Radio Shack item