190D eating glow plug relays

[jaoneill]

I could really use some help on this one; electrical problems are really not my forte.

Pre-glow timer (glow plug relay) on my '84 190D daily driver crapped out back in early November. Replaced it with one of the new and improved "upgrade" relays. It lasted less than a month, died last Friday. Borrowed the relay from my '85 190D, installed it Friday afternoon, all worked as it should. Have started the car maybe 15-20 times since and it now appears that this relay is cooked. Came out of a 2 hr lunch meeting today and had no glow light (or glow plug action; almost didn't start).

Can't imagine what is causing these things to fail, but fail they have. On Friday when I installed the latest relay in the '84 I also tried the two previously inop relays in the '85, with no results, so I am relatively certain that they are dead.

I have another relay on the way from Phil, but at $164 apiece I almost hate to install another one in the '84 if there is something else that may be causing these premature failures. Prior to this I have had no glow problems at all.

Saw a post by rrgrassi indicating that QC may be an issue with these relays but the last one the '84 cooked was not new and had been working just fine in the '85.

Any advise sincerely appreciated,
Jim

[barry123400]

Easy stuff first. Check all the resistances of your glow plugs as one may be almost a dead short. That should have taken the strip fuse out though so is probably not a good candidate. Next I would find the relays ground leg. If this has some resistance it may be shunting more current through another circuit in the relay to attempt to complete a ground than it was designed to take. It may pay dividends to open up one of the now defunct ones and see what if anything has overheated and burnt out.. Thats where I would start first. It might give you a clue as to what is happening.

[jaoneill]

Thanks Barry,

Will open up one of the inops and see what there is to see. Will also check the plugs but, as you have indicated, they are probably ok, with one glow cycle it didn't spin a full turn this morning before it started (at ambient 11f).

Jim

[jaoneill]

Duh,

Hey Barry, your first easy thing was an excellent shot, I didn't get much further than getting an inop relay off the shelf. Strip fuse under the cover is blown. As you advised, next step glow plugs (and a new strip fuse).

Thanks a million, Jim

[Samuel M. Ross]

Originally Posted by jaoneill

Duh,
Hey Barry, your first easy thing was an excellent shot, I didn't get much further than getting an inop relay off the shelf. Strip fuse under the cover is blown. As you advised, next step glow plugs (and a new strip fuse).
Thanks a million, Jim

Jim,
Your plight is exactly why IF/WHEN I face a relay/timer replacement, I'm going to retrofit my 240D with a manually powered GP system that merely has a pushbutton somewhere on/under the dash. As I see it this would also serve as a theft deterrent!

Be certain to let us know what you find... shorted GP, whatever!
Regards,

[Parrot of Doom]

Where can I buy the strip fuses from? I have an OM606 glow plug relay with a couple of these burnt out. I could replace them and sell it.