78 300SD glow relay location? - PeachParts Mercedes-Benz Forum

imagesinthewind · #1 01-09-2009, 05:01 PM

It's cold out and I need to replace my glow relay on the 78. Taking it off the 79. So I would love it if someone would save me the time of standing in the cold looking for the location of the replay.
Just want to move quick.
I hate winter. . .

Thanks!
Ginny

uvula · #2 01-09-2009, 08:09 PM

The GP relay in my '83 is behind the driver side headlight just in front of the wheel well. Pretty sure it's the same in a '78 but I don't remember 100%. I'd check there first.

Lycoming-8 · #3 01-09-2009, 09:26 PM

Gosh, we thought that you had fallen off the edge up there.

The 116 chassis is somewhat different from the W126, so the relay may even have a slightly different configuration as well as location. At least if it did not change, the general appearance of the one in the 300D should give you guidance.

How is the Florida car running?

LAbioCars.com · #4 01-09-2009, 09:49 PM

its a silver box attached to the steering under the dash
i believe

rs899 · #5 01-10-2009, 07:30 AM

Ginny-

How ya been?

You are getting some conflicting info ...but nobody here so far has a 78 300SD. I don't either, but on my '80 300SD (also W116) the relay is in the engine compartment between the driver's side headlight and inner wheel well. Since the glow plugs on all SDs were pencil type (right?) I don't think they had any reason to move the relay from under the dash like they did on the 300D and 240D. Anyway- look there first- its easier.

Rick

Oracle12345 · #6 01-10-2009, 08:25 AM

under the dash

imagesinthewind · #7 01-10-2009, 04:34 PM

Quote:

Originally Posted by Lycoming-8

Gosh, we thought that you had fallen off the edge up there.

How is the Florida car running?

Hey!
I've just been up to my ears in busy.
The bar manager we had quit so I went there full time.
Full time in the bar biz is 24/7. I finally got the place
back to square and hired a couple more people so now
I only work 12/7.

The Florida car is Tom's daily driver. Smokes 4 packs
a day so it won't pass inspection but well. . .lets just
say we found a way around that. He just better not
get pulled over.

My car needs either new glows (though the current ones
are only a year old) so I'm figuring the relay.

And I'm afraid that the tranny is going to need work.
It hasn't been driven in 4 months so it might be that
the tranny needs to just be used, but I think a flush,
filter and fill may be in order and some crossed fingers.
It hesitates from a stop and sometimes does this studder
or pulsing thing. I cold checked the ATF and it's in the
good range, which means it's low. I'll try to start it
and check it at temp and see what the real deal is.

Sorry I fell off the MB planet. I have been driving
the Yukon (don't hurt me) since my car has been
so hard to start and just no time to get her fixed.
I DID get the motor mount fixed so the jackhammer
sound is gone.

But life is easier and less stressfull now so I'll hangout
more.

imagesinthewind · #8 01-10-2009, 04:37 PM

Quote:

Originally Posted by rs899

Ginny-

How ya been?

You are getting some conflicting info ...but nobody here so far has a 78 300SD. I don't either, but on my '80 300SD (also W116) the relay is in the engine compartment between the driver's side headlight and inner wheel well. Since the glow plugs on all SDs were pencil type (right?) I don't think they had any reason to move the relay from under the dash like they did on the 300D and 240D. Anyway- look there first- its easier.

Rick

Hi Rick!!!!!

Thanks for the location, I think that's where it is.

I'm glad to know I was at least a little missed. I missed you all
a lot and wonder often how you all are and how the cars are
running.

Wish it was warmer, I hate being cold.

Gonna go check that relay and hopefully switche 'em out.
I am yearning to drive MY car instead of the Yukon.

Thanks again,

300dmichael · #9 01-10-2009, 08:55 PM

rs899 is correct. I have a 1978 300 sd and if you follow the wires from the glows back, they lead right to the relay on the left fender well,just to the aft of the headlight..

Jim W. · #10 01-11-2009, 06:27 AM

1978 300SD
To add to the location on the LF fender wall; there is a black box and the glow plug relay is inside this box.

Jim W.

rs899 · #11 01-11-2009, 06:38 AM

Pay attention to the condition of the strip fuse under the cover of the relay. If it looks at all suspect, replace it. Check on the one you are swapping in.

Diesel911 · #12 01-11-2009, 12:42 PM

Quote:

Originally Posted by 300dmichael

rs899 is correct. I have a 1978 300 sd and if you follow the wires from the glows back, they lead right to the relay on the left fender well,just to the aft of the headlight..

This is a excellent and extremely logical suggestion!!!

imagesinthewind · #13 01-11-2009, 04:11 PM

I did find it but it isn't the relay. Or the 79 relay doesn't work with my car.
The 79 had two more wires into the relay than my 78 does.
When I switched them out, there was no glow light in the dash.
Put the old one back on and the light came back.

Here are the symptoms, maybe I'm wrong. . .

*Hard Hard starting even on the warm days.

*Glow light but at one time the ignition needed turned several times before the light would come on at all. Now it comes on all the time but the plugs don't seem to glow.

*Car starts right up when it's plugged in. Even last night at 20 degrees, just one glow.

*Plugs were replaced in Jan 2007. Hard starts began in May 2007.

Oh, and tranny is fine now. I think the sitting for 4 months was the problem. I let it warm up well today and drove it in the 'hood for 5-7 miles. It smoothed out and seems normal. Checked ATF and added about 4-5 ounces. Seems all good. WHEW!