Name this relay

[LOW DOUGH]

I was cleaning up the engine bay in my 71 by removing wires that don't do anything. I found some that aren't doing anything and they go to this relay. What are they for? What is does this relay do?

[1972SUPERSB]

It is your horn relay. Well maybe not its in a different spot.

[Already Gone]

It looks like the Speed Warning Dash relay to me and even seems to be in the right spot for it. Now the thing is you say its on your 71 and I am very certain the Speed Warning Dash wasn't an option after 1969.

[SS Tim]

Located above your disconnected horn relay is the TCS (Transmission Controlled Spark) timing relay. As far as being redundent, that would all depend on how complete and functional your truck is. The system explanation is a little better in the 72 service manual than the 71.

[VetteVet]

Copied from another thread.




Re: Transmission Controled Spark
TCS uses a speed switch in the transmission and an engine temperature switch to control a time-delay relay mounted on the inside of the firewall near the horn relay to turn on and off a solenoid valve that disables vacuum advance to your distributor.

Power is supplied by a brown/white wire that comes from the square fuse panel connector.

Two wires plug into the TCS solenoid valve (mounted on the intake manifold): brown/white & dark blue.

The brown/white and the dark blue wires then run through the firewall to the time-delay relay.

A black wire runs from the time-delay relay back through the firewall and connects to the transmission switch.

A second dark blue wire runs from the solenoid valve to a temperature switch mounted in the passenger side head.





The horn relay is below the TCS time delay relay and to the right, The red green and black wire harness goes to the horn relay.

[LOW DOUGH]

Originally Posted by SS Tim

Located above your disconnected horn relay is the TCS (Transmission Controlled Spark) timing relay. As far as being redundent, that would all depend on how complete and functional your truck is. The system explanation is a little better in the 72 service manual than the 71.

Thanks. I was just curious. My truck is not complete as in it's not original. It seems to have all been peaced together. I think the cab is a 72 because of the things a 72 had different from the other years.

Also I need to fix the horn button. That's why the horn relay is unplugged.

[LOW DOUGH]

Would this relay be on a six cly, 3 on tree truck? I think not. That's what my VIN calls for. I still have the clutch/brake pedal assembly under the dash. I bought the truck with a 350/TH350 combo in it.

[SS Tim]

Why not? They were installed pretty much across the board in C10s due to vehicle gross weight classification. But to directly answer your question yes a 71 6cyl/3OOT truck would have had the TCS (or CEC) system.
Might want download a manual or two if you don't have them to more completely understand how your truck was built and what systems were used above the minimum required to run the engine.
An example of this would be if you have a functioning Neutral Safety Switch for you current trans installation.

* VIN/Model Decoders
* Power Team Charts (engine/transmission/gear ratio)
* Post Your Pickup SPID Blazer SPID Suburban/Panel SPID
* RTFM ... Read The Factory Manuals... download 'em here

[LOW DOUGH]

Yeah... the neutral safety doesn't work on my truck.

[LOW DOUGH]

Thanks for the info SS TIM.