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Discussion Starter #1
I have been trying to solve my high idle problem on a 1985 380 sl I just purchased. I ordered a new overload protection relay because I read this solved the problem on other people cars with the same problem as mine. Put it in no help, but the strangest thing now is that the car won’t shut down unless I pulled the Relay.
 

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Discussion Starter #3
The car will not shut down either with the old relay with a new fuse in it or with the brand new relay . I just ordered one more relay just Incase it was bad from stock. I need to look at a wiring diagram and see what the relationship is between the overload protection relay and the engine control module and ignition system.
 

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You won't find an electronic engine module. You have an idle control unit/relay, and idle control valve. The relay gets input from temp. sensor. I can't remember which one. Do you have ABS?
 

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Input comes from an oil and coolant temperature sensor. Coolant lives on the rear of the block near the passenger side firewall (rhd) . If you're in a country that drives leftly it's on the driver's side.

Oil temp sensor lives near the oil filter cannister. Remove that to access.

I think this issue might be caused by a faulty ignition switch (where you put your key in). I would check the wiring on him.
 

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Input comes from an oil and coolant temperature sensor. Coolant lives on the rear of the block near the passenger side firewall (rhd) . If you're in a country that drives leftly it's on the driver's side.

Oil temp sensor lives near the oil filter cannister. Remove that to access.

I think this issue might be caused by a faulty ignition switch (where you put your key in). I would check the wiring on him.
Unless you have move lately you are in a LHD country.
 

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Discussion Starter #8
Thanks for the reply, but don’t you think a faulty ignition switch would give me problems all the time. My situation happened when i tried to replace the burnt fuse on the overload protection relay. With a good fuse on that relay the ignition will not shut down when I turn key to off.
 

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What happens when you close the doors?
There was a video posted recently of a 560 that will start normally but when you remove the key the engine shuts only when the door is closed.
It would be funny if it does.
 

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I had this symptom when I did an experiment on my aux fan. Details don't matter but the problem was in a circuit I built that unintentionally bridged battery bus power (circuit 30) with start run bus power (circuit 15) when the aux fan was running (aux fan switch grounded). When you look at the wiring diagram, see if you can find an item that uses power from both buses - might lead you to a feedback fault that causes this undesired bridge.

Is there any non-factory electrical item in your car? If so, how is it powered and grounded? If you isolate it, does your symptom persist?
 
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