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Rear-Defrost Relay

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Old 11-15-2013, 08:19 PM
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Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Rear-Defrost Relay

Does anyone know of a replacement p/n for the rear-defrost relay? I can only find used ones on Ebay and I don't trust 30 year old relays..lol The relay under the passenger dash, not the on/off button.

My issues is my rear-defrost doesn't stay on more than 2 min at a time. Doing research here on the boards I've come to the conclusion that my issue is the relay. It still "clicks" when I turn it on and off, but it should stay on for much longer than 2 min at a time.

Last edited by Ozz1967; 11-15-2013 at 08:34 PM.
Old 11-18-2013, 08:01 AM
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Re: Rear-Defrost Relay

No one knows of a good replacement relay for the rear defrost?
Old 11-18-2013, 04:50 PM
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Car: LOWERED ♦ CRIMSON METALFLAKE
Engine: ► 400 KUBES ◄
Transmission: 765R4
Axle/Gears: EATON POSI 4.56
Time Out

You won’t find one unless it’s dealer NOS.

If the 2 minutes is repeatable it’s not the fault of the relay, it’s the timer.

The following circuit can replace your defective timer:


C1 and R1 control the amount of time.

Start with 270μf
* for C1, and 8.2K* for R1.

I estimate 5 minutes for the aforementioned.

If more time is desired increase C1 and or R1.

To make it easy you can use a potentiometer for R1 so you can dial in the time wanted.



*Or the closest you can get.


Happy Racing!



Even Tho I Might Destroy The Car During The Race, At Least It Looks Gorgeous At The Start

Old 11-18-2013, 05:18 PM
  #4  
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Car: 1984 Trans Am
Engine: LS1383 in work
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Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Re: Time Out

Originally Posted by NINÅ
You won’t find one unless it’s dealer NOS.

If the 2 minutes is repeatable it’s not the fault of the relay, it’s the timer.

The following circuit can replace your defective timer:


C1 and R1 control the amount of time.

Start with 270μf
* for C1, and 8.2K* for R1.

I estimate 5 minutes for the aforementioned.

If more time is desired increase C1 and or R1.

To make it easy you can use a potentiometer for R1 so you can dial in the time wanted.



*Or the closest you can get.


Happy Racing!



Even Tho I Might Destroy The Car During The Race, At Least It Looks Gorgeous At The Start

From everything I've read, the timing circuit is in or is part of the relay. Is this not correct?
Old 11-19-2013, 04:58 PM
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Car: LOWERED ♦ CRIMSON METALFLAKE
Engine: ► 400 KUBES ◄
Transmission: 765R4
Axle/Gears: EATON POSI 4.56
Time Out

Yes so it might be easier to replace the relay and timer.

Nomenclature evolves and people refer to the entire assembly as a ‘relay’.


Happy Racing!



Even Tho I Might Destroy The Car During The Race, At Least It Looks Gorgeous At The Start

Old 11-19-2013, 06:04 PM
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Car: 1989 Iroc-Z Camaro
Engine: TBI,5.0
Transmission: Automatic 700R4
Axle/Gears: Eaton Posi,3.42,LPW Ultimate Cover
Re: Rear-Defrost Relay

I’m also looking for a timer, or at least I was. It rained today so I thought I would give it another try. The darn thing worked. The light was on at least 5 min. and I could slowly start to see through the window. How long it will last is another story.

Last edited by Ron U.S.M.C.; 11-19-2013 at 06:14 PM.
Old 11-19-2013, 06:07 PM
  #7  
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Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Re: Rear-Defrost Relay

Originally Posted by Ron U.S.M.C.
Hmm, not a bad price really...never know with old parts though. Like mine, it works...just not well.
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