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09-24-2010, 04:14 PM
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#1 |
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72 GMC
Join Date: Feb 2008
Location: Wells, Maine
Posts: 534
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What is the relay above and to the left of the horn relay on my 72 ?
What is the relay above and to the left of the horn relay on my 72 ?
Blue wire, black wire, and a brown with a white stripe ? The PO did funny things to some of the wiring on this truck. Thanks |
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09-24-2010, 04:43 PM
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#2 |
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Registered User
Join Date: Jul 2001
Location: North Louisiana
Posts: 4,501
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Re: What is the relay above and to the left of the horn relay on my 72 ?
I believe that one controls the emissions, believe it or not! I think the relay controlled the vacuum going to the vacuum advance for better emissions in high gear or something like that.
__________________
Wynne 70 CST short fleet Hugger orange & white, 350/350, ps, pb, air, tilt, tach/vac/speedwarning, original buckets, AM/FM, oak bed floor, shoulder belts, 3.5"/5.5" drop, 20" American Racing VN425s. Build thread 53 Chevy shortbed 69 Camaro Click here to subscribe Chevy GMC International Truck Club Louisiana Charter Member http://www.louisianaclassictruckclub.com |
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09-24-2010, 05:01 PM
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#3 |
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72 GMC
Join Date: Feb 2008
Location: Wells, Maine
Posts: 534
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Re: What is the relay above and to the left of the horn relay on my 72 ?
that might explain why it is soldered to itself and fed back through the firewall, really going nowhere except back on to itself.
thanks |
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09-24-2010, 09:54 PM
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#4 |
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Registered User
Join Date: Jun 2006
Location: Indiana
Posts: 4,859
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Re: What is the relay above and to the left of the horn relay on my 72 ?
Search for TSC or transmission spark control. There is a recent thread that has a picture of a relay under the dash. Yea, it gets confusing because the vacuum switch is usually gone, and or, other parts. My truck had all the parts, but I removed it all.
The relay grounded through the temperature switch in the passenger side head. If the temp was 32 or higher, the switch was closed. Then the power wire fed through a switch in the trans sensing high gear. If both switches were closed, power was fed to a vacuum switch located near the card which allowed vacuum to reach the vacuum advance canister on the distributor.
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'70 GMC C1500 LWB Power disc brakes. WooHoo! Posi 6 Lug Dana 60 Last edited by ERASER5; 09-24-2010 at 10:03 PM. |
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09-24-2010, 09:50 PM
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#5 |
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its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: What is the relay above and to the left of the horn relay on my 72 ?
yep. I can never remember what it was called, but the dist would not get full vac untill the trans was in top gear amd the engine at full operating temperature. Then the relay would trip and let the engine get full advance.
most truck got this ripped out decades ago |
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