Hi Guys, another glow plug question, but with some unique qualities...

Just recently I've noticed that my pre-glow indicator light on my 85' 300D N-T has been acting strange. When I turn the ignition sw. to run position on a cold day, the PreGlow light will not come on till about 6-7 seconds after I turned the key. Then it would go out 1 or 2 seconds after that. On warm days the light would not come on visibly at all. In either case, the car starts normally, but immediately idles slightly rougher that it did before this problem (at least for the first few seconds).

What I am wondering, is this some type of indication that a Glow plug may be damaged/gone-bad or is this problem just a slow relay or a bad connection? Does a separate relay power the illuminator and if so, where is it?

I pulled the GP relay out and opened it up, cleaned contacts and all connections to it and around it. The relay does click and energise the GPs whether or not the light comes on. Also, if I immediately turn the key to stop when running, and then back to run, the light works normally and will do this for about the next 5min or so, then works as stated above.

I've just returned from an 800mi trip with my MB, so I'm thinking that maybe the extended 75-80mph driving broke a plug or rattled something loose??? Otherwise the car handled the extended stress fantastically and even runs better now than before (less smoke too).

Thanks

ATLD

Any ideas???