Rear Defogger Not Working
Thread Starter
TECH Regular
Joined: Jun 2019
Posts: 497
Likes: 43
From: Hatboro, PA 19040
Rear Defogger Not Working Is this the right section for this question?
When I bought this 2000 Trans Am last year, the rear defogger does not work at all.
The switch lights up when pressed -- then nothing happens.
Been looking this morning at Cell 61 FSM on the rear defogger.
Inspected the two connectors on the glass, they looked ok so far visually.
So far I'm thinking to test for power at those connectors.
Then thinking my first go to's might be a ground, the flexible harness on the hatch where the wire(s) move when you open or close the hatch, or the electronic switch might have a bad relay or bad solder joints.
Anyone know common problems with this circuit or any diagnostic ideas?
Thank You!
Lee
When I bought this 2000 Trans Am last year, the rear defogger does not work at all.
The switch lights up when pressed -- then nothing happens.
Been looking this morning at Cell 61 FSM on the rear defogger.
Inspected the two connectors on the glass, they looked ok so far visually.
So far I'm thinking to test for power at those connectors.
Then thinking my first go to's might be a ground, the flexible harness on the hatch where the wire(s) move when you open or close the hatch, or the electronic switch might have a bad relay or bad solder joints.
Anyone know common problems with this circuit or any diagnostic ideas?
Thank You!
Lee
Joined: Nov 2003
Posts: 11,330
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
The most common problem is failure of the 30A circuit breaker. Swap in a 30A fuse (it will plug in exactly the same) and see if the defogger starts working. Also, replace the 20A HVAC fuse while you're at it (visual inspection can be very misleading so replacement is a cheap and reliable way to check a fuse).
Beyond that, the most common issue is with the connections at the grid. Use a multimeter to check for power on one side and ground at the other. It would be extremely unlikely to have a problem in the wiring unless something was done to disturb it. And the relay is not a replaceable part - it's part of the HVAC controls... not that it couldn't fail but it would be very expensive to replace.
Beyond that, the most common issue is with the connections at the grid. Use a multimeter to check for power on one side and ground at the other. It would be extremely unlikely to have a problem in the wiring unless something was done to disturb it. And the relay is not a replaceable part - it's part of the HVAC controls... not that it couldn't fail but it would be very expensive to replace.
Thread Starter
TECH Regular
Joined: Jun 2019
Posts: 497
Likes: 43
From: Hatboro, PA 19040
Thank you! Thank you again! This is perfect information!
Will check on those. Was thinking a wiring issue would be more rare. I'm telling you the connectors on the glass "look" great so far. lol
Lee
Will check on those. Was thinking a wiring issue would be more rare. I'm telling you the connectors on the glass "look" great so far. lol
Lee
