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Discussion Starter · #1 ·
I've checked my wiring diagrams and I know there have been a lot of posts on this topic but I can't seem to find the answer.

I got a new forward lamp harness from M&H for my 70 396/350 4 speed. I know that the portion of the harness that's covered with a black tar impregnated tube and terminates with an L shaped connector with 2 green wires in it connects to the driver side temp sensor. My question involves one of the 2 green wires in the tube. It looks like one of them comes directly from the bulkhead connector and is wrapped in black tape with the rest of the harness until it is fed through the tube and into the L connector. The other green wire looks like it does not originate in the bulkhead connector bundle but it is wrapped in with the rest of the harness. It exits the taped portion of the harness as a bare green wire about 3 inches from the bulkhead connector and terminates with a male spade in another L shaped connector. The other opening in that connector has nothing in it. The question is...where does this one go? It's not on my old harness but that one's been hacked over the years.

Man, it's tough to describe a harness, I hope the question is clear enough that it makes sense.

Thanks.
 

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Could this possibly be for the a/c compressor? They are usually one dark and one light green. One comes from the switch the other goes to the fast idle solinoid on the carb. But it is usually a flat connector.
 

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It is part of the TCS circuit. The correct temp switch would have two switches in one. One for the indicating light which is routed through the bulkhead connector. The other one, the one in question is the ground for the TCS relay.
 

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Several things don't add up. In 1970 there were two temp sensors. One on the drivers side that has a single dark green wire and terminal connection. The other in the passenger side head (TCS) with a single dark green wire to one terminal then a jumper to the other terminal. The connection to the TCS sensor is the L shaped connector. The connection to the temp sensor should be a single connection.
The green wire from the bulkhead connector is the temp light or gauge wire. The TCS green wire goes to the TCS override relay mounted on the firewall. This connector should have the green wire and a dark blue wire in it. The dark blue wire goes to the TCS vacuum controlled solenoid.
Bottom line is this. Most 70's have had all the TCS stuff removed. What you want is the green wire from the bulkhead connector hooked to your temp switch.

[This message has been edited by Steve S (edited 04-12-2002).]
 

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Discussion Starter · #5 ·
Thanks for the responses. I don't have A/C so I don't think that's it. Sounds like the wire in question goes to the TCS relay but since I'm not including the TCS system on my restoration, I'll just tape it off.
 

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The TCS pair of green wires is on the passenger side (more or less, depending on what's been done inside the engine compartment), there would be a pair of relays on the firewall just above the distributor. There is a large green wire for A/C, and a smaller green for the temp sending unit, both of these would be on the driver side.

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Cecil Hawkins
San Diego, CA
1971 GMC Sprint
The Project
All I need is time...and some $$$
"Tourist, go home! And take someone with you!"
 

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Steve

I agree, this may help. Sometimes the left hand temp switch has the TCS switch. In this case it is a min temp switch which gave full vacuum advance until the coolant temp reached a min temp. In other cases the TCS temp switch is on the right hand side. In this case it is a min and max temp switch giving full vacuum advance when the coolant temp is below a min or above a max. The green wire from the TCS solenoid with the L shaped connector and a jumper, as you described will connect to the right side mounted temp switch or it will also connect to the “mystery wire” connector. I think that the right hand temp switch was used on the big block or with the gauge package. M&H sells one forward lamp harness for all V8s (without gauges) so the wire is there if needed.

Like you stated most 70s have the TCS removed.


[This message has been edited by Elree Colby (edited 04-12-2002).]
 
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