AL WTB 1971 under hood wiring and relays - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**JQ-72** · 05-31-2019, 01:46 PM

Looking for these pictured relays and wiring harness that goes with it. They are mounted just above where the parking brake cable goes through the firewall.

**70STOVEBOLT** · 05-31-2019, 04:16 PM

What are the relays used for?

**JQ-72** · 05-31-2019, 04:21 PM

Quote:

Originally Posted by 70STOVEBOLT

What are the relays used for?

Good question - I'm not sure? Most all of my trucks are '72s and they have similar relays under the dash by the fuse panel. I've seen these external relays on '71 trucks before so I'm pretty sure the set up is from the factory. Neither under hood wiring harness looked like it had connectors that would go to these relays.

beautimus · 05-31-2019, 05:14 PM

im not sure but i think 1 of them is the tcs (transmission controlled spark relay)
most of the trucks that i have seen have had those wires cut off the harness at the relay.

**70STOVEBOLT** · 05-31-2019, 09:08 PM

My 70 had the TCS solenoid near the heater box

**rechinca** · 06-01-2019, 01:56 PM

It’s 2 relays and a harness for the TSC. If you want good ones they are available new from several of the catalogs. They are not needed and just an early attempt at pollution control. I would hazard a guess most people just remove them or they have been hacked up. In order to work you also need the pieces that are on the transmission, a unit on the intake manifold and the temp sensor/sender in the head. Unless you’re restoring, I’d just remove the remaining items. The sensor in the head is in a water jacket so drain the block before removing and installing a pile plug.

**JQ-72** · 06-01-2019, 04:54 PM

Quote:

Originally Posted by rechinca

It’s 2 relays and a harness for the TSC. If you want good ones they are available new from several of the catalogs. They are not needed and just an early attempt at pollution control. I would hazard a guess most people just remove them or they have been hacked up. In order to work you also need the pieces that are on the transmission, a unit on the intake manifold and the temp sensor/sender in the head. Unless you’re restoring, I’d just remove the remaining items. The sensor in the head is in a water jacket so drain the block before removing and installing a pile plug.

Thanks for the information. I'll still look for an original set up, but I can continue my engine install without it for now.

**rechinca** · 06-01-2019, 05:34 PM

I can’t be sure the 2 relays on mine were any good, but I have them both and I’ll be glad to send them your way free of charge. They are just sitting in my parts box right now.

**JQ-72** · 06-01-2019, 05:47 PM

That's awesome! I'll PM ya.

**painterljp** · 06-02-2019, 09:10 AM

I dont know what it is for either but our 71 has it. Cant be transmission related as ours has a 3 on the tree. Factory. And a 307. No power brakes and no power steering. Unmolested. Cant get a better picture right now in paint jail.

05-31-2019, 01:46 PM	#1
JQ-72 Senior Member Join Date: Feb 2001 Location: Killen, Alabama USA Posts: 3,572	WTB 1971 under hood wiring and relays Looking for these pictured relays and wiring harness that goes with it. They are mounted just above where the parking brake cable goes through the firewall. Attached Images __________________ 72 Cheyenne Super swb. Factory 402/400,tach,posi,AM/FM, A/C. Adding cruise, 8-track 72 Cheyenne Super swb. 350/350 A/C, bucket seats 72 Cheyenne swb. Factory 402/400, tilt, posi, A/C 72 Cheyenne Super K-10. 350/4 spd., posi. 72 Suburban 350/350 tilt, tach, AM/FM, A/C, luggage rack 72 GMC Sierra lwb. 350/350, A/C. medium green/olive interior

05-31-2019, 04:16 PM	#2
70STOVEBOLT Senior Member Join Date: Jun 2005 Location: Winona Lake, IN Posts: 6,258	Re: WTB 1971 under hood wiring and relays What are the relays used for? __________________ 70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Power windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear

05-31-2019, 05:14 PM	#4
beautimus Registered User Join Date: Mar 2002 Location: woodstock, alabama, usa Posts: 938	Re: WTB 1971 under hood wiring and relays im not sure but i think 1 of them is the tcs (transmission controlled spark relay) most of the trucks that i have seen have had those wires cut off the harness at the relay. __________________ i survived cancer and kidney stones, but my kids are killing me.

05-31-2019, 09:08 PM	#5
70STOVEBOLT Senior Member Join Date: Jun 2005 Location: Winona Lake, IN Posts: 6,258	Re: WTB 1971 under hood wiring and relays My 70 had the TCS solenoid near the heater box __________________ 70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Power windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear

06-01-2019, 01:56 PM	#6
rechinca Senior Member Join Date: Jul 2018 Location: Vacaville, CA Posts: 528	Re: WTB 1971 under hood wiring and relays It’s 2 relays and a harness for the TSC. If you want good ones they are available new from several of the catalogs. They are not needed and just an early attempt at pollution control. I would hazard a guess most people just remove them or they have been hacked up. In order to work you also need the pieces that are on the transmission, a unit on the intake manifold and the temp sensor/sender in the head. Unless you’re restoring, I’d just remove the remaining items. The sensor in the head is in a water jacket so drain the block before removing and installing a pile plug. __________________ 1971 Custom/10 - 350/3 speed, Orange/White roof

06-01-2019, 05:34 PM	#8
rechinca Senior Member Join Date: Jul 2018 Location: Vacaville, CA Posts: 528	Re: WTB 1971 under hood wiring and relays I can’t be sure the 2 relays on mine were any good, but I have them both and I’ll be glad to send them your way free of charge. They are just sitting in my parts box right now. __________________ 1971 Custom/10 - 350/3 speed, Orange/White roof

06-01-2019, 05:47 PM	#9
JQ-72 Senior Member Join Date: Feb 2001 Location: Killen, Alabama USA Posts: 3,572	Re: WTB 1971 under hood wiring and relays That's awesome! I'll PM ya. __________________ 72 Cheyenne Super swb. Factory 402/400,tach,posi,AM/FM, A/C. Adding cruise, 8-track 72 Cheyenne Super swb. 350/350 A/C, bucket seats 72 Cheyenne swb. Factory 402/400, tilt, posi, A/C 72 Cheyenne Super K-10. 350/4 spd., posi. 72 Suburban 350/350 tilt, tach, AM/FM, A/C, luggage rack 72 GMC Sierra lwb. 350/350, A/C. medium green/olive interior

06-02-2019, 09:10 AM	#10
painterljp Senior Member Join Date: Nov 2014 Location: Albuquerque NM Posts: 901	Re: WTB 1971 under hood wiring and relays I dont know what it is for either but our 71 has it. Cant be transmission related as ours has a 3 on the tree. Factory. And a 307. No power brakes and no power steering. Unmolested. Cant get a better picture right now in paint jail. Attached Images



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