I have a hunch that replacing my GP relay this winter is the reason I now have no power to my AC compressor. Yak told me in another thread that the starter can disengage a relay that powers the compressor, to prevent excessive battery drain during starting.

I had assumed this meant the ice cube relays on the DS fender. But I was thinking about it last night, and I always hear the GP relay click at start.

I also read about how pin 50 on the GP relay is the violet starter signal wire and after a recent starter replacement have laid hands on the violet wire where it connects to the starter.

Can anyone confirm whether a faulty or miswired GP relay could prevent the AC compressor from getting power? I have no power as far back as the fuse.

This is a rebuilt relay for the old loop style plugs I bought from a company in NC over the winter.

Also, any ideas about how to diagnose whether this is the problem would be very much appreciated by this sweaty Texan!

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

I am not sure I follow the other parts of your description but the Viiolet Wire ends up being connected to the Same Terminal on the Starter Solenoid that the + Wire from the Ignition Switch goes to. If you have a Neutral Safety Switch the Switch is bteween the Ignition and the Starter Solenoid.

On the Turbo W123s a White Wire (don't know if it has a strip) comes up from the Small Solenoid Terminal to a Wire Junction/Terminal Block and the Violet Wire is screwed in top of it.

What happens when you pull the Plug on the Glow Plug Relay?

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84 300D, 82 Volvo 244Gl Diesel

I guess I am asking how the starter controls voltage to the compressor - how does it prevent the compressor from engaging during the starter cycle?

I know the terminal block you are talking about - my wagon melted it!
I am not sure if my 240D has that or not....There is a violet wire on the small solenoid terminal though.

If I pull the GP plug, I wouldn't get glow and will have trouble starting -or do you mean after I have the car running?

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

I guess I am asking how the starter controls voltage to the compressor - how does it prevent the compressor from engaging during the starter cycle?

I know the terminal block you are talking about - my wagon melted it!
I am not sure if my 240D has that or not....There is a violet wire on the small solenoid terminal though.

If I pull the GP plug, I wouldn't get glow and will have trouble starting -or do you mean after I have the car running?

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

I have been told on the Forum only the Turbo models have that particular Terminal Block.
The Violet Wire goes directly to the small Terminal on the Starter on the 240D.

My best guess is that the Ignition Switch decides what does not get power during Starting.
Other than that I don't know.

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84 300D, 82 Volvo 244Gl Diesel

How does that violet wire work? It is connected to the small terminal of the starter, so when the starter engages, I guess to grounds out the other accessories that are normally on in the 'run' key position? Why does it connect to the GP relay though?

I guess I need to do some wire tracing...hate that job....argh.

Sorry for the double post

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

The + voltage from the Ingnition Switch goes to the Soldenoid Terminal to activate the Starter Solenoid; at that time the + voltage goes to the Violet wire and turns the Glow Plug Relay on during Cranking.
When you release the Key the Starter Stops and so does the Voltage to the Glow Plug Relay going through the Voilet Wire.

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84 300D, 82 Volvo 244Gl Diesel