Help with Glow Mystery
 

1987 300 T
Out of the blue the glow plug indicater light doesn't light and the car won't start.

Has always started very quickly on the 1st turn of the starter.

It was maybe 25 F last night.

Thanks in advance.

Bernie

Guess
 

Glow plug relay?
Fuse 80 amp?
Coolant temp sensor?

Thanks

Bernie

Hi Bernie, I think you're on the right track . Remove the 80 amp fuse and check it for cracks . Check that you have battery voltage at the connection coming to the relay.Pull the connectors (to gp's and to dash) and clean them up . The ground should be removed and cleaned up as well. Once all the connections are good then start testing the system as per the manual.Good luck.

Thanks Kyle
 

I am operating without a manual.
Mine were just uneducated guesses.
I cannot even recall where the 80 amp fuse is located.
Maybe my declining mempry will kick in.

Any idea why this would happen suddenly?

Flawless operation and dependability until now.

Thansk again.

Bernie

The 80 amp fuse is on the preglow relay, it's a strip of aluminum about an inch long. The relay is on the driver's side fenderwall towards the front. The fuse is held in place by two screws and it might look OK but remove it and check for cracks or corrosion around the screws. If you've had no trouble before that and the other connectors are good there is also the OVP relay behind the battery on the 124. It has a 10 amp blade type fuse on the top of it under a little flip up cover. Also check the fuses in the fuse box , remove them and clean them up if they have any corrosion at all.I have a 124 manual if you need to dig any deeper , good luck.

Kyle II
 

The OVP is about 2 months old.
The glow fuse is 3 years old.
I am hoping a fuse.

Thanks again.

Bernie

Hi Bernie, welcome to the wonderful world of MB electrical gremlins. One thing that may be obvious but I haven't mentioned yet is the battery. Check the posts on top to make sure they're clean (between the post and terminal) as well as the battery ground attachment. I cured a bunch of glitches by removing the ground cable bolt and cleaning under the cable terminal where it attaches to the body. I sprayed the connection with fluid-film to stop any further corrosion. This suggestion may seem a little archaic but try turning on the key and then tap on the relay, sometimes the contacts in the preglow relay just need a good smack ;) .

Very likely the fuse, the 300D did this to me last year. Also locked up the starter, but I don't think the two are related particulary!

Peter

Fuse
 

Fues is melted, now how do you get a screwdriver in there to change it?

Can't find the only 90 degree one that I own.

Thanks.

Bernie

I no longer remember how I got the fuse in and out. Can you unclip the relay from the fender maybe? I don't remember any difficulty.

My fuse was melted too, for whatever reason. Works fine now.

Peter