rear window defrrost need help please
Thread Starter
Junior Member
Joined: Oct 2014
Posts: 41
Likes: 0
From: millsboro,de
Car: 1986 firebird
Engine: 305 v8
Transmission: auto
Axle/Gears: 2.73 ?
rear window defrrost need help please
my 86 firebird rear window defroster button will come on when it wants to. sometime you push it it lights up . sometimes times nothing ! when it does come on it does,t defrost the window. now that we,re getting frost it would be nice that it worked and being diabled its kinda rough scrapeing it . any help,info would be greatly appreciated !!! thanks ron
Supreme Member
Joined: Jan 2006
Posts: 3,341
Likes: 10
From: Mooresville NC
Car: LOWERED ♦ CRIMSON METALFLAKE
Engine: ► 400 KUBES ◄
Transmission: 765R4
Axle/Gears: EATON POSI 4.56
Lost Defrost, What’s The Cost
Sounds like multiple problems with the switch assembly.
There might be debris in the unit causing the high impedance input to be triggered, turning on by itself.
When you cannot turn on when you want might be due to a bad internal connection such as a cold solder joint.
Even tho the lamp lights the grid might not be getting power.
With the key off use an ohmmeter to make sure the right-side hatch support wire is grounded.
With the key on turn the defog button on and if the lamp illuminates use a voltmeter to see if the left-side hatch support wire is getting power.
If it isn’t, are you getting power on both sides of the defog circuit breaker?
The breaker is located in the Fuse Block Panel, which is located up and to the left of the brake pedal, behind a small door.
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing !
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
If Speed Limits Were Any Lower They Would Be Negative Numbers
There might be debris in the unit causing the high impedance input to be triggered, turning on by itself.
When you cannot turn on when you want might be due to a bad internal connection such as a cold solder joint.
Even tho the lamp lights the grid might not be getting power.
With the key off use an ohmmeter to make sure the right-side hatch support wire is grounded.
With the key on turn the defog button on and if the lamp illuminates use a voltmeter to see if the left-side hatch support wire is getting power.
If it isn’t, are you getting power on both sides of the defog circuit breaker?
The breaker is located in the Fuse Block Panel, which is located up and to the left of the brake pedal, behind a small door.
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing !
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
If Speed Limits Were Any Lower They Would Be Negative Numbers
Supreme Member
Joined: Nov 2009
Posts: 1,255
Likes: 54
From: Lincoln, NE.
Car: '87 IROC
Engine: 5.7 Vortec w/ factory TPI
Transmission: WC T-5
Axle/Gears: 3.45 Posi
Re: rear window defrrost need help please
I had this same issue and I ended up having to fix the grid. Bought a kit from the local parts store that included a stencil and some metal paint. If you end up needing another switch I have one in my horde of parts.
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