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1977 450SL
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50 Posts
Discussion Starter #1
Purchased my 77 450SL a few months back and need advice on how to correctly wire the Thermo Time Switch and Cold Start Vave.

here is a quick picture of the current wiring loom.

I am in need of a diagram to hook up the appropriate sequence.

The current temp sender wire and warm up regulator wires are self explanatory as they are currently hooked up, problem is that leaves 1 wire to hook up to the Thermo Time Switch and Cold Start Injector Valve. I have the correct Thermo Time Switch plug (brown with 3 wires) and the correct Cold Start Injector Valve connector (blue with 2 wires), but cannot figure out how to wire those 2 items correctly with just one remaining wire. Any help you can give me would be greatly appreciated.
 

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Registered
1977 450SL
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50 Posts
Discussion Starter #3
You should find an appropriate wiring diagram in here...

Model 107
Thanks, I've been through that and many more places.

Is there anyone that could look at their similar year and tell me where/how the five wires are connected to the factory 4 wire harness?

Thanks
 

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'89 300TE, '79 450SL, '01 ML320
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1,051 Posts
The connector at the thermo-time switch has two terminals with three wires, two pink/blue wires on one and a brown on the other.
One of the pink/blue wires is going to the main harness (the one you had hooked to the cold start valve originally).
The other pink/blue and the brown go to the cold start valve.




Fish
 

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1977 450SL
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Discussion Starter #5
The connector at the thermo-time switch has two terminals with three wires, two pink/blue wires on one and a brown on the other.
One of the pink/blue wires is going to the main harness (the one you had hooked to the cold start valve originally).
The other pink/blue and the brown go to the cold start valve.




Fish
Thank you very much, the only thing I could tell from the wiring diagram I seen was that the solid brown was the ground, and the previous owner had all these wires clipped and rerouted for some odd reason. Appreciate the reply.
 

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'89 300TE, '79 450SL, '01 ML320
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Yes, the cold start valve picks up it's ground when the thermo time switch 'grounds out'.
It could be that the thermo time switch is bad and the PO didn't have a clue how the system works?
Also the thermo time switch must be installed without any thread sealant, for obvious reasons :)



Fish
 

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107
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420 Posts
The current temp sender wire and warm up regulator wires are self explanatory as they are currently hooked up, problem is that leaves 1 wire to hook up to the Thermo Time Switch and Cold Start Injector Valve. I have the correct Thermo Time Switch plug (brown with 3 wires) and the correct Cold Start Injector Valve connector (blue with 2 wires), but cannot figure out how to wire those 2 items correctly with just one remaining wire. Any help you can give me would be greatly appreciated.
Iam not clear what exactly you mean by “ but cannot figure out how to wire those 2 items correctly with just one remaining wire.

Here are the wiring to the thermo-time switch (12) and cold-start-valve (13)

Wire color code:
Rs/bl = pink/blue
Br/bl = brown/blue

Hope it helps!

 
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