Hi,

I drive a 1999 C220CDI with 120000miles on the clock.

I have started to have the glow plug light come on imediately after
starting and it stays on for about a minute before switching off.

It makes no difference if I hold the ignition before starting to allow
them to warm up, they come on every time.

Any ideas what might be causing this as it has never happend before.

Thanks