W164 heat coil

[SBurnett]

Car: ML320 cdi 2006

First thing in the morning I put the key in the ignition and the heat coil comes on. After it goes out I switch the engine on and the light goes out for just a second but then comes on and stays on for a few minutes before going out again. I've looked in the car handbook but nothing on what it could be.
Anyone know?

 

[jaymanek]

you have one or more glow plug burnt out.

 

[alexander patie]

as jay says, sadly quite common on the 642 engine.