The Stovebolt Site Forums The Shop Area The Electrical Bay '71 Chevy - What are these for?

Looks like factory wire harnesses going to the relays. Did GM offer a factory trailer wiring harness in 71?

I agree that it all looks to be factory, from the relays to the harness. I have no idea if GM offered factory trailer harnesses back then, but about anything is possible I suppose. The harness was running down the firewall and was tucked in between the cab and inner fender, but I have no idea if that was where it was supposed to run or not. It's all a huge mystery to me.

The one on the left looking at the photo is the horn relay. The other might be a circuit breaker for something optional or added on.

Wiper and horn relays,
Scott

On '71's the horn relay is in the cab, close to the fuse box. I have also been told that these relays and harnesses are for the original Transmission Spark Control emissions stuff. Beats me, but I know all the other emissions stuff is missing or unhooked, so that may be it for all I know.

Bear,

I don't know nuttin about much but I don't think your horn relay would be inside the cab. This sort of defeats the whole purpose of that item, near as I can tell.

I haven't heard of a 'Transmission Spark Control' on a '71 pickup either, but I have been OTL before.

Stuart

I believe Bear is right. I know they did start putting the horn relay inside the cab somewhere in that era. It just hangs on the wires by the fuse block. They did have some type of TSC in the early years of emission controls. The connectors on that one unit look like horn relay connectors.

I have to correct myself, it's TCS (Transmission Controlled Spark) instead of TSC. I was close...lol... Anyway, it's been tough to find info on that system. All I know at this point is that it kept the distributor from advancing until the tranny was in high gear and the engine was warmed up. It reduced emissions very slightly but also increased fuel consumption considerably. I have yet to see any pics of the system completely hooked up, or even a diagram for that matter.

I do wonder, though, if one of those relays is an anti-dieseling relay. I have seen a single pic of that and it looks similar to the one on the left side, like a horn relay. It's tough to tell what this truck was originally equiped with since the original carb is gone. I did think it was the horn relay as well, until I found that the horn relay is in the cab. I'm doing a lot of learning with this '71.

Get a book!