There is only sort of a general idea of if your GP controller will work or not. If you have a 1976 model probably not because of the results reported on this forum.

With a 1979 most seem go have reported it working but not all. Can't tell you why except that there is rare occasions when Mercedes has used another companies relay instead of bosch.

You might take a look at what amperage the fuse on the wall has.

This is just a general observation not particular to you. I have noticed in the last 3 years a trend of member who won't go to the repair links to read up on their issue and expecting a one sentence answer. Also they are not interested in owning a Factory Service Manual or even going to one of the internet sites where the Factory Service Manual is free. (However, in this case the updated Glow Plugs are not in the Factory Service Manual.)

Note that the complete Glow Plug Update kit used to come with a different Glow Plug Regulator for those instance when the original did not function correctly. However, so much time has passed I don't know if that Glow Plug Rely is even sold separately.

Repair Links

Fast navigation http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

Anyway the good news is you have a long time before winter to deal with it.

__________________
84 300D, 82 Volvo 244Gl Diesel

You could also put a Starter Solenoid or a Ford Glow Plug Solenoid/Relay between your stock Glow Plug relay.
I don't know if your relay stock GP relay would function normally but all of the amperage to the Glow Plugs would go through the Starter Solenoid which is made to take a much higher amperage then any Mercedes Glow Plug Relay.

What is shown in the pic is one that I bout on my Volvo Diesel which had an aluminum box type Glow Plug Relay similar to the ones on the older Mercedes. I simply count how many seconds I wish to apply the Glow Plugs and then start.

Note that my system has no fuse in it. They sell 80 amp blade type fuses and holders for people you put high amp amplifiers/speakers in their Cars.

Attached Thumbnails

 

__________________
84 300D, 82 Volvo 244Gl Diesel

I would recommend using a newer glow plug relay from a 1980 on model for your conversion.
The thread below has some info on wiring the 4 prong plug on the newer relays.

Fast Glow for my 76 240 D

__________________

76 240 D. Bought in 1998 for $25.
85 300D. Got it for free with a bad engine. ( Sold )
60 Unimog 404. What was left of it, was given to me. Now powerd by 617A.
88 560 SEL. Bought without engine and trans. Now powerd by 617A.
67 250 SE. Cuope. For resto or sale.
64 220SE. For resto.

Quick follow up for everyone's benefit. I have the dash pepper pot indicator in my 76 240D Euro model. I installed the Bergsma "fast glow system" i.e. Monark pencil plugs with wires. I deleted the earthing wire at the end and used a hand brush to clean out any carbon in the glow plug holes.

I can safely state that everything worked well. No replacement relay or fuse and no issues whatsoever. Starts are faster (duh!) and crisper. All in all, a really fantastic upgrade, one I'm really happy with!

__________________
Why I will never do business with "DieselKraut" again

http://www.peachparts.com/shopforum/mercedes-benz-used-parts-sale-wanted/378935-why-i-will-never-do-business-dieselkraut-again.html

I ha e same car! They are awesome aren’t they ? I did the same thing when I got mine. It’s much better.

The next step is to rob a glow Plug Relay and harness off a newer 80s 616 or 617. . Use your original controller wire that plugs into the first glow plug as the switch for the relay and run the harness harness to your plugs and get rid of the series wires.

Now you have parallel and most important after glow which is really nice. I just did this to my 1975 300d runs smoother after it starts.

I just