Anybody know what this is for ?

[hayhauler71]

I am going through my original wiring harness on my 71 chevy c10 350 3 speed manual trans has no ac, ps, pb I ran across this wire that is dark brown in color that comes out of the bulkhead and was in the firewall gutter and not used. It is key on fed and the wire is only 12 inches long and will not reach the engine at all. I have looked at the wiring diagram and in the bulkhead there is only 1 brown wire that is for the voltage regulator and this is about 5 feet short. Any ideas I really would just like to know what it is used for. Here is a pic of the wire and the plastic connector. Thank You

[magwakeenercew2jh]

Don't take this one to the bank, but I think that's the juice for a tranny kick-down. I had an extra brown with that connector
on my original harness. And the fresh M & H harness has one, too. I just let it "dangle" in a safe place and called it good.

[med.bronze]

I actually think that's for the TCS harness, it plugs into it
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[magwakeenercew2jh]

Originally Posted by med.bronze

I actually think that's for the TCS harness, it plugs into it
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Cool. I have absolutely *no idea* what a TCS is.

[med.bronze]

Transmission controlled spark. The harness itself plugs into the trans, a temp sensor on the pass. side of the engine, a idle solenoid on the carb and two relays on the firewall above the emergency brake on the outside in 71 and the inside in 72. Most guys throw um away
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[asolde]

My first thought was it goes to the brake porportion valve being so short?

[hayhauler71]

Originally Posted by asolde

My first thought was it goes to the brake porportion valve being so short?

Brake proportioning valve wire is tan and that is hooked up and works

[magwakeenercew2jh]

Yeah. It's for the trans.

Not a kick-down plug.
But a plug for the trans none-the-less.



I don't use it with my TH350. I'd make a safe bet that the manual trans doesn't use it either. But what do I know?

One thing's for sure: On *my* truck, you can let it "run wild".

[Ed 72 Sierra Grande]

Mine is dangling free also. The last 42 yrs

[SS Tim]

How does REF ACC FEED sound to everyone? What wiring diagrams did you use the generics or the 71 service manual's?

[71K20chevy]

My '71 has the same wire as well, I posed a topic on the forum quite some time ago and I think we all came to the conclusion it was for the TCS. Like said above, it's usually thrown away as it is just emission crap that makes the truck run poorly when it is not warmed up, if I recall.

[69gmcc10]

Originally Posted by SS Tim

How does REF ACC FEED sound to everyone? What wiring diagrams did you use the generics or the 71 service manual's?

Tim, what is the REF ACC FEED?

[SS Tim]

Originally Posted by 71K20chevy

My '71 has the same wire as well, I posed a topic on the forum quite some time ago and I think we all came to the conclusion it was for the TCS. Like said above, it's usually thrown away as it is just emission crap that makes the truck run poorly when it is not warmed up, if I recall.

While there is a TCS in many 71 applications it is too easy to dismiss any wire as smog related. If there is a wire question it needs to be identified against an applicable schematic. In this case it would be very easy to trace it back to the connector cavity to confirm.

Originally Posted by 69gmcc10

Tim, what is the REF ACC FEED?

Actually I had not noticed it before nor seen if referenced. From the description it is an underhood igniton voltage reference power connector for testing that can also be used for an underhood accessory feed.

[69gmcc10]

Thanks Tim! I personally find the wiring on these trucks to be interesting to say the least! My stock wiring harness has radio wires piggy backed off trans wires that are plugged into the radio fuse spade, who would have know they had anything in common.