Hi Each
I have a problem with the glow plug circuit on my 2008 ML280CDI. When I turn on the ignition, regardless of the ambient temperature (it has been -10c here this week) the glow plug light comes on for less that a second before going out. I have checked with a circuit tester on a glow plug and the feed to the plug is of the same duration. I have changed all the plugs and the controller with new units, I have even replaced the oil temperature sensor which is in the glow plug circuit, all to no avail. I still get the same outcome.
Is this a problem or is this normal? If I wait a few seconds after the light before turning the key the car starts normally.
TIA

 

What temperature does your car think it is? Sounds like it thinks things are at least room temperature. A good scanner should be able to accurately answer the question, then you can work towards finding the offending part (temp sensor is my guess).

 

As stated in my original post I have replaced the temperature sensor with a new one and it has made no difference. I have scanned the car with an OBD reader and there are no error codes.

 

Is the oil temp sensor the only temp sensor in the circuit? or is the ambient sensor involved? or coolant sensor?

I think these sensors also provide the dashboard data, so if your dash temps are reading normally for coolant and ambient, i think that mean those sensors are reading correctly. I could be wrong though. maybe an ECU issue of some kind?

or a ground issue? I've seen someone have a ground issue related to the glow plug circuit, loose ground solved all the problems.