Hello all,

How to I test the glow plug relay to determine if it is bad? I don't know where it is located. Is it easy to change?

What is the part number for the glow plug relay?

Thank you very much.

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1998 E300 Turbodiesel 184K

The relay is on the driver's side directly behind the windshield fluid bottle. It is a rectangular black unit (approx. 4"x2"x2") with multipin plug from the glow plug harness and a hot red lead screwed to a post. The MB Part # should be 022-545-75-32 .
I replaced the original one on mine back in Feb. just for good measure and it cost $142.00.......kept the 10 year old one for a back up.

What makes you think that yours is bad? Are you getting a CEL and code/message ? Trouble starting? Unplug the glow plug harness first from the Relay and check each glow plug with an ohm meter before you replace the relay. There are plenty of
threads on that subject.
Cheers

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K

Go to dieselgiant.com and follow the GP testing procedures therein for the W123.

Same principals apply for your engine. Very easy.

Is your CEL lit up or is the GP light staying on?

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Thsnks for the reply, I just finished getting all of the glow plugs out and I am getting ready to replace all of them.

I was reading some posts and one of them mentioned that a bad relay will burn out glow plugs. I really don't think I have a bad relay, but I want to test it. Maybe I should change it for peace of mind???

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1998 E300 Turbodiesel 184K

Consider that the rest is all down hill. Those glow plugs can make you lose a few hairs, and the fact that you have them all out should ease your worries. Good luck !!

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96 E300d

You have definitly got the most difficult task under control...removing the glow plugs. If you take in consideration that the Glow Plug Relay is probably 10 years old and how many times it has cycled......I would change it out....it does not owe anyone anything........ Use your anticpated "Bush Bucks" to buy a new relay and you'll be good for another 10 years

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K