W210 E320 CDI heater light

[W124ali]

I have a 2000 E320 CDI. The heater light comes on when I turn the ignition on. It switches off for a second and then remains on. This is the heater coil light on diesels.
What could be the issue? What to check first?

Thanks

 

[bob6600]

Either glow plugs, the relay, or both.

Can be checked with a diagnostic check or a multimeter

The old relays have a fuse link that could also have blown