Relay Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hondo66 · 08-09-2015, 09:01 PM

What are the 2 relays on engine side of firewall behind the hood hinge on drivers side? My 71 is a wiring nightmare everything is wire nutted together using red wire. The wires out of these relays are just cut off and wadded between firewall and inner fender.
The previous owner installed a cheap gauge set that doesn't work and I'm trying to get factory gauges working again.

brad_man_72 · 08-09-2015, 09:28 PM

Aftermarket ad on. Good luck.

**fat dan** · 08-09-2015, 11:45 PM

They may have been for the headlights, one for the high beam, and one for the low beam. Also could have been for fans or road, fog lights.

**Jason Banks** · 08-10-2015, 09:08 AM

Sounds like the Transmission Controlled Spark relay's

See this thread:

http://www.stovebolt.com/ubbthreads/...&Number=544501

**Jason Banks** · 08-10-2015, 09:12 AM

Here's another thread on this site:

http://67-72chevytrucks.com/vboard/s....php?p=7040140

Davidf · 08-10-2015, 10:46 AM

Yes, both relays on a '71 are for the Transmission Controlled Spark feature. The relays on my '71 are still bolted to the firewall, but long since abandoned in place as are most I would bet.

hondo66 · 08-10-2015, 09:57 PM

Yeah that's them all right. Mine only have a brown wire hooked to the harness and they used the black for a ground to a switch under the dash.
Thanks for everyone's help.

08-09-2015, 09:01 PM	#1
hondo66 Registered User Join Date: Aug 2015 Location: missouri Posts: 2	Relay Question What are the 2 relays on engine side of firewall behind the hood hinge on drivers side? My 71 is a wiring nightmare everything is wire nutted together using red wire. The wires out of these relays are just cut off and wadded between firewall and inner fender. The previous owner installed a cheap gauge set that doesn't work and I'm trying to get factory gauges working again.

08-09-2015, 09:28 PM	#2
brad_man_72 the boat guy Join Date: Jul 2007 Location: springfield mo Posts: 2,339	Re: Relay Question Aftermarket ad on. Good luck. __________________ 67, swb, fleet, tach, throttle, 5.3, 4l60e, 3.73's, fuel cell, 5 lug, p.d.b., 4-6 drop. great little truck 66, stevens drag/ski 18' silouette, 350, 2.02 doublehump heads. comp extreme marine 278 cam, vette 7 fin valve covers, old polished edelbrock intake, velvetdrive, casale v-drive, adj cavitation plate. 28, model a rpu project,

08-09-2015, 11:45 PM	#3
fat dan Keep on Trucking Join Date: Nov 2012 Location: Tryon, Ok. Posts: 44	Re: Relay Question They may have been for the headlights, one for the high beam, and one for the low beam. Also could have been for fans or road, fog lights.

08-10-2015, 09:08 AM	#4
Jason Banks Senior Member Join Date: Dec 1999 Location: TX Posts: 1,542	Re: Relay Question Sounds like the Transmission Controlled Spark relay's See this thread: http://www.stovebolt.com/ubbthreads/...&Number=544501

08-10-2015, 09:12 AM	#5
Jason Banks Senior Member Join Date: Dec 1999 Location: TX Posts: 1,542	Re: Relay Question Here's another thread on this site: http://67-72chevytrucks.com/vboard/s....php?p=7040140

08-10-2015, 10:46 AM	#6
Davidf Registered User Join Date: Nov 2014 Location: Austin Posts: 749	Re: Relay Question Yes, both relays on a '71 are for the Transmission Controlled Spark feature. The relays on my '71 are still bolted to the firewall, but long since abandoned in place as are most I would bet.

08-10-2015, 09:57 PM	#7
hondo66 Registered User Join Date: Aug 2015 Location: missouri Posts: 2	Re: Relay Question Yeah that's them all right. Mine only have a brown wire hooked to the harness and they used the black for a ground to a switch under the dash. Thanks for everyone's help.



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