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Old 12-26-2017, 09:01 PM   #1
CAJ1971
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Relays

Can anyone tell me what these 2 relays are that go on firewall on Drivers side?
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Old 12-26-2017, 09:03 PM   #2
CAJ1971
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Can anyone tell me what these 2 relays are that go on firewall on Drivers side?
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One has part number 3990843
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Old 12-26-2017, 09:10 PM   #3
rockyrivermark
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Re: Relays

I'm guessing horn relay.
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Old 12-26-2017, 09:13 PM   #4
truckster
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Re: Relays

Most likely the horn relay and TCS (if it's a later year - I think TCS was only 71 and 72).
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Old 12-26-2017, 09:32 PM   #5
CAJ1971
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Quote:
Originally Posted by CAJ1971 View Post
Can anyone tell me what these 2 relays are that go on firewall on Drivers side?
Posted via Mobile Device
One has part number 3990843
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Old 12-26-2017, 10:51 PM   #6
CAJ1971
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Re: Relays

I was thinking horn relay too but it looks like I have one already under the dash. Should be fun to figure out. Gotta love wiring.
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Old 12-28-2017, 12:21 AM   #7
heskahoka
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Re: Relays

Looks to be a Transmission Controlled Spark Solenoid. It is designed to not allow vacuum advance until you are in a higher gear and the engine is up to temp. A very primitive emission control device.

Found some info here:
https://www.ebay.com/p/NOS-GM-1971-C...0843/658409486

Here:
https://www.autozone.com/repairguide...00c152800515a5

And Here:
https://www.corvetteforum.com/forums...-solenoid.html
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Old 12-28-2017, 12:29 AM   #8
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Re: Relays

Quote:
Originally Posted by truckster View Post
Most likely the horn relay and TCS (if it's a later year - I think TCS was only 71 and 72).
What he said...
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