DIY 1980 preglow relay upgrade - PeachParts Mercedes-Benz Forum

Kyle Blackmore · #1 11-02-2003, 07:58 PM

I'm sure I'm not the only one out there who has run into this problem. 1980 was the year MB upgraded from the filament style glow plugs to the pencil type.The new system also used an engine mounted sensor for the relay (as in the old ), then in 8/'80 they upgraded the relay again to include the temp sensor inside the relay. The old style also had the temp gauge sending unit routed through the relay, the new relay doesn't . The only cutting of the original harness' is to splice the temp gauge wires together (circuit B).I wanted to upgrade my system to eliminate the very expensive ($500Cdn) original relay and this Bosch unit also will afterglow the plugs for up to 3 minutes after the car is running, depending on the temperature under the hood.

Kyle Blackmore · #2 11-02-2003, 07:59 PM

another pic

Kyle Blackmore · #3 11-02-2003, 08:17 PM

another pic

Kyle Blackmore · #4 11-02-2003, 08:20 PM

another picture...

Kyle Blackmore · #5 11-02-2003, 08:21 PM

and another pic...

Kyle Blackmore · #6 11-02-2003, 08:23 PM

another picture

P.E.Haiges · #7 11-03-2003, 04:47 AM

Kyle,

You dates are a little off. The pencil GP were used on the USA 300SD in 1978 when it first appeared. It also had the temperature sensor to determine how long the GP dash light stays on.

I know, I have a '78 300SD.

P E H

Stevo · #8 11-03-2003, 12:54 PM

I also thought "80" was the first year for the fast GPs, still think it is for 240D anyway.

I got this kit for my daughters "78" 240D. When she came home for the week end I installed it except for the relay, which I hate to admit, but I never did figure out those directions

and she had to get back to the city. I used the old relay and she glows it for 10 seconds or so. It made a HUGE difference in cold starting

Kyle Blackmore · #9 11-03-2003, 10:02 PM

PEH- my mistake, of course the S-class got them before the 123. I assume your car has the same type of relay as the 123 , this upgrade would work for those models as well.

Kyle Blackmore · #10 11-03-2003, 10:07 PM

Stevo- does your daughter's 240D have the large diameter glow plugs or the newer style? When I bought my kit I briefly saw a kit to swap the filament style to pencil type gp's. I assumed it had a relay similar to the one I installed.

Stevo · #11 11-03-2003, 11:06 PM

Kyle....Ya the "78" & "79" had the larger GPs. The only differance is the size, well they do cost about $20.00 +ea.... I would think the relay would be the same. Keep us posted, maybe I will get inspired to hook up the daughters relay when she comes home next.

Steve

P.E.Haiges · #12 11-04-2003, 06:09 AM

Kyle and Stevo,

I have '78, '79 and '80 300SDs and they all take the same GP. I noticed there were different and more expensive GP for earlier 300SDs listed in the Fastlane online catalog but I ordered the lower cost Bosch GP. They are interchangable on all my 3 cars. I think they are the smaller ones, seems like a 12 or 13 mm wrench was used to change them.

The GP relay is the same as shown in the pictures above on all my 300SDs. The 2 300SDs I use start fine so I'm not about to replace anything.

P E H

Stevo · #13 11-04-2003, 10:33 AM

PEH.. Humm

"more expensive GP for earlier 300SDs"

Those larger (18mm) GPs must be the ones I got. I thought they were about twice the price of the (12mm) smaller ones. The differance they made in starting was will worth it, then some. Now you got me to wondering if there is a differance between the reguler (fast) GPs and the "after glow" GPs, as in an up greaded version to take the extra load of the "after glow" feture. I am thinking there is and that is all they are producing now?

Steve

P.E.Haiges · #14 11-05-2003, 05:10 AM

Stevo,

My 300SDs don't have an after glow setup. I think that came much later than 1980.

I never saw parallel (pencil type) GP larger than the ones I have but that does not mean they don't exist. The older series (loop style) were larger, probably 18mm. My 190D thru 240D had the series type GP.

Stevo · #15 11-05-2003, 01:46 PM

PEH

Guess I wasnt very clear. I was wondering if the new "after glow" system plugs were differant than the older plugs. Both being the pencel, new style as opposed to the loopers. I think I answered my question with a visit to Fastlane parts. I gather that all pencel style (12mm or 18mm) plugs are the same. With the after glow systwm they wont last as long however. Sorry to drag this out but I was never really clear about this after glow. Anyway I hope to never see another loop plug or resistor wire

Steve