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Discussion Starter · #1 ·
'71 chevelle malibu, 355/th350, idiot lights with AC and all the tcs goodies. Have installed after market guages. Want to use the idiot lights as well. I can't find the plug or wires for the temp sending unit. How do I go about running the temp guage for just the idiot light? Can I wire this through one of the relays on the firewall? Sending unit has a 2 prong connection.

Also trying to figure out a strange noise when the iginition is turned off. A couple of seconds after the car is turned off I hear a noise from the dash. When ever I re-connect the battery I hear it as well. Not quite a buzz or clunk but sounds like something is engaging/disengaging.
Thanks for the help
 

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Dear Matty. I have a 70 ss and just finished my engine bay. On the 70 wiring diagram you will see on the driver's side fender well a dark Green wire that goes to the Temperature sending unit. When your key is on you should have 12 volts to this wire. Attach this wire to a ground screw and see if your idiot light comes on. This will simulate you temperature sending unit heating up. If it does not work, check the bulb behing you idiot light and the circuit board. This usually works. Now if you want to run both the gage and the idiot light look for an additional spot on your manifold to tie into for your after market gage. I just did all that on my 70 ss. I believe the 71 wiring is very similuar.
 

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Discussion Starter · #3 ·
Having a hard time finding that wire. Never had the origianl temp idiot light since I have owned it. Before I start digging thru the wire harness is there an alternate way to do it? I have a 2 prong sending unit marked G/R. There are 2 green wires that go to the idiot light, one from the temp sender and one from the tcs relay. Can I connect the temp sender to the green wire from the tcs relay? If so which prong on the sending unit do I need?
 

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There are (or can be) 2 green wires on the idiot light but one of those wires doen't go to the TCS relay. TCS has nothing to do with the hot light. The green idiot wire needs to go to the "R" terminal on the temp sender. R is the "red light" terminal.
 

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Originally posted by ASB:
Hi All. If I remember right some of the TCS stuff uses the temp sender to ether engage or disengage the relay when the car was cold.
True to a degree. He mentions a second terminal on the temp sender. This is the "G" terminal. This is another switch inside the temp sender that is independent of the "R" terminal. Chevy could have used two different senders, installing one in the right head. One for the idiot light in the left head and one for the TCS in the right head. However, they decided to use 2 switches inside the same sender.
 

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Discussion Starter · #7 ·
I do have 2 green wires coming from the temp light, need to do some more digging in the wire harness to find the right one. Trying to trace the wire from the tcs relay back to the sender. Going home for the holidays, will check the old motor for the harness. Can't see why I would have cut it.

I do have a anti-dieseling relay and a blocking relay behind the glove box. One of these was causing the strange noise. I do not have the AC installed. Do either of these relays effect anything else but the AC compressor? Thanks for the help.
 

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One of the green wires, from the TEMP idiot light goes to the bulkhead connector and heads over to the sender. The other dark green wire, from the idiot light, goes to the ignition switch. This is the idiot light test wire.
Those 2 relays were used on an A/C car and can be bypassed if they aren't functioning.
 

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In the early 60's Chev used a 2 wire ( hot & cold ) idiot light sender with a second green idiot light to show that the engine was cold. Warm up car before driving hard. they later used that sender for the TCS.
 
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