Problem with rear defroster
Thread Starter
TECH Enthusiast
Joined: Oct 2002
Posts: 553
Likes: 0
From: Long Island, NY
Problem with rear defroster Alright, my stupid rear defroster will not work 
. I pulled the fuse and that was not the problem. Does anyone have any idea what else it could be?
. I pulled the fuse and that was not the problem. Does anyone have any idea what else it could be? Thread Starter
TECH Enthusiast
Joined: Oct 2002
Posts: 553
Likes: 0
From: Long Island, NY
Come on guys. I replaced the breaker with a 30 amp fuse and it still doesn't work. My power seat still works right so I figured that wasn't the problem. When I push the button to turn the defroster on, nothing happens. The light doesn't even turn on for a split second. This is really pissing me off. 
TTT
TTT
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Joined: Nov 2003
Posts: 11,334
Likes: 347
From: Jacksonville, FL (originally from Toronto Canada)
There could be any number of things wrong...
There are two fuses (actually a fuse and a circuit breaker) used to make the defogger work. The circuit breaker is called "DEFOG / SEATS" and the fuse is 20 amps called "HVAC". Either one could prevent the system from working.
If those are OK then check the switch to make sure you have 12V at the pink wire when the ignition is on (if not, find the break in the feed wire). Then check that there is 12V at the switch on the gray wire when the switch is pressed (if not, replace the switch).
Next, check the defogger timer/relay which is mounted to the back of HVAC control panel for power at the pink wire when the ignition is on and power at the gray wire when the defogger switch is pressed (if not, find the break in the wires). Then check for power at the orange wire at all times (battery supply). If not, recheck the circuit breaker and check for a break in the orange wire somewhere. Check that the black wire provides a good ground (if not then just splice in a good ground wire). Finally, check that the purple wire starts showing 12V after power has been applied to the gray wire when the switch is pressed (if not then replace the timer/relay).
If all of that seems to be working then you either have a broken connection between the timer/relay and the window grid or else the window grid itself has some broken elements. Check for power on the purple wire at the rear window (if not then find the break in the wire) - while you're at it check for ground on the black wire at the window. Otherwise, take it to the dealer who can fix broken spots in the grid with a special liquid silver compound designed for that purpose.
The only thing you need to test all this is a test light or a multimeter and some time - well, probably quite a bit of time...
There are two fuses (actually a fuse and a circuit breaker) used to make the defogger work. The circuit breaker is called "DEFOG / SEATS" and the fuse is 20 amps called "HVAC". Either one could prevent the system from working.
If those are OK then check the switch to make sure you have 12V at the pink wire when the ignition is on (if not, find the break in the feed wire). Then check that there is 12V at the switch on the gray wire when the switch is pressed (if not, replace the switch).
Next, check the defogger timer/relay which is mounted to the back of HVAC control panel for power at the pink wire when the ignition is on and power at the gray wire when the defogger switch is pressed (if not, find the break in the wires). Then check for power at the orange wire at all times (battery supply). If not, recheck the circuit breaker and check for a break in the orange wire somewhere. Check that the black wire provides a good ground (if not then just splice in a good ground wire). Finally, check that the purple wire starts showing 12V after power has been applied to the gray wire when the switch is pressed (if not then replace the timer/relay).
If all of that seems to be working then you either have a broken connection between the timer/relay and the window grid or else the window grid itself has some broken elements. Check for power on the purple wire at the rear window (if not then find the break in the wire) - while you're at it check for ground on the black wire at the window. Otherwise, take it to the dealer who can fix broken spots in the grid with a special liquid silver compound designed for that purpose.
The only thing you need to test all this is a test light or a multimeter and some time - well, probably quite a bit of time...
