There is a module under the upper left rear quarter trim that controls the Defroster and the FM Radio... Assuming you have check for power coming out of the defroster relay, my bet is this module is shot (which is somewhat common)

BBEngineer

 

In the case of the '06 Impala, it was the fuse panel under the hood. To my knowledge, my '94 Monte Carlo has all the rear defroster fuses/relay on the passenger side fuse panel.

 

I heard rumor of some cars that have the radio antenna in the glass (much like the rear defroster grid) having some sort of relay between the two.

Come spring, I intend to re-check everything on my Monte (as it's been so long since I looked at this problem, I don't remember all the results found and right now the car is tucked in for winter, tough to do anything on).

I do recall the relay for the rear defroster found in the passenger side fuse panel tested good and we know it gets power coming into the relay. I don't recall the results found testing the wiring in the back.

Do you happen to have a part number for that module you mentioned?

Thanks!!

 

Bump!
I found some information that talks about changing the radio antenna/defroster module, but I can't find any steps to trouble shoot that module nor can I find a replacement part number anywhere for it.

Anyone have any additional information about that module? Thanks!

 

I don't have the part number for the module, but if you Pm ZSPOT on NAIOA, he'll get you the part number (and great pricing)

For diagnosis, check for power on the large green wire going into the module when the defroster is on... if you have power and the defroster doesn't work, it's likely the module

If you don't have power, I would guess it's the circuit breaker for the rear defroster (try unplugging the module from the grid, then check for power on the green wire, if you have power after disconnecting the grid, it's likely the circuit breaker)

The breaker is located on the BACK of the passenger side fuse block. You can get to it from the back by dropping the glove box to gain access

BBEngineer

 

Thanks BBEngineer!! That's the info I was looking for. I will hit up ZSPOT soon! I don't yet know if that "solves" my problem (and I won't be looking at it again until closer to spring), but it's a LOT more info and MUCH more useful then what I've had previously!

 

had the same problem back in 04 intimidator. figured out when someone was cleaning the rear window, they accidently hit the plug to the defroster and my buddy just sawdered it back on and it was fine.

 

the rear defroster on my 2004 quit working. after searching the web and this site for answers I think I may have found my problem. behind the fuse block on the passenger side of the dash there is a circuit breaker for the rear window defroster. You'll have to open the glove box door ,, remove the little lanyard that holds the door up and let it swing down. squeeze the glove box and it will clear the little stops and the glove box will swing fully down. looking in the glove box opening on the right hand side you will see just beyond a metal brace a tin circuit breaker. THIS IS NOT THE CIRCUIT BREAKER FOR YOUR REAR WINDOW DEFROSTER. however, just below that circuit breaker, out of your line of vision you will FEEL the rear window defroster circuit breaker. Mine was completely disintegrated. the plastic base was crumbling and the metal shell definitely showed of extensive heat. Why this circuit breaker failed and literally burned up I do not know ,,, but local auto parts stores don't carry a suitable replacement. So after I get a replacement from a GM dealer and somehow get it back in I'll see if my defroster begins to work again. If this circuit breaker burns up I guess I'll be searching the wiring harness for defects. Oh yeah, the metal circuit breaker that you can see ,,,, that's for your power seat.

 

I know my friend's sister has an '06 Impala that had 2 problems with the rear defroster circuit (and this does not apply to my Monte). In the passenger side kick panel is a wiring harness and GM used an underrated connector (seperate the plugs and the part of the plug for the rear defroster is black). Fix for that is cut the two wires and connect them outside of that wiring harness. The other problem on that car was the fuse panel. Even though no one had toughed any of the fuses, the forked connectors for the relay that controls the rear defroster had seperated and they were not making complete contact. We took the fuse panel out, tore it open and squeezed the forks tighter together. Since all that, she's been running great all winter.

Duke0466, you are the first to mention the circuit breaker on the Monte. Thanks for the info! I am going to be following what BBEngineer mentioned, the module in the back that splits the defroster and the antenna.

 

If I can offer some helpful advice (I live in Canada I know about defrosting) there is a site called frost fighter I tried all the other window tab kits out there from acdelco, permatex, etc. this one worked I looked extensively at wiring diagrams, pulled panels off the interior, checked voltages, and what I came up with was the tabs hadn't fallen off completely but were loose and caused high resistance. There was no module on my 2003 and I looked trust me. And I checked 2002 and 2004 also just cause I was flipping out. Frost fighter is a two part high silver content epoxy and was the only thing that worked for my experience. Came from Colorado and cost me $31.XX including shipping.