Do NOT use a lesser size breaker. A lot of juice flows through that, so a smaller amp breaker may yield nothing.

Also, the breakers can and do wear down as they age. Unless you have a way to prove it works, get a new one from the parts store (they are cheap). When I put mine in, I have to trim the legs of the new one (they were too wide for the spot on the fuse block).

I took a look at the schematics and if I'm reading them right, after you activate the rear defroster, the relay should trigger and the circuit breaker should have power coming into it. If you can get power going in and power going out of the circuit breaker, then that leaves the radio antenna module or a problem at the rear glass.

 

So in order, the current goes from the switch button, to the relay, to the breaker then in the radio antenna module.

The antenna module, would I have a bad radio reception too or is it separate in the module? Because i have a real good reception.

I can't hear the relay, I'll try a few more test tomorrow.

Can you post the diagram or send it to me via e-mail?

 

I attached the schematic for the defroster in the '05 Monte.

As for the current, you have a piece incorrect. When you push the button, only a small amount of current passes through (not the 12v). That current is used to trip the relay. As you may recall, one leg of that relay is hot at all times (that is power coming from the battery). When the button is pushed, it causes the relay to now connect that 12v from the battery to the circuit breaker.

As for the radio reception, from what little I know about that radio antenna module, if you get bad reception on the radio when the defroster is on, the module is bad. But after that, it's a hard to tell. I would assume you'd have to verify you are getting power to the module first before determining it's bad.

 

Thank you.


I removed the HVAC module from the dash and opened it to see if there was something wrong but just by looking I couldn't tell so I put it back together and in it's place. I also remove every fuses one by one in the passenger fuse panel and they were all good. Then I tried a 3rd relay just for the fun of it (I already had tried a 2nd one the other day with no luck) and it worked


So I put the original relay back and now it works too . I guess I may had a bad connection somewhere and I fixed it when unplugging/plugging everything.


By the way, I dont have the radio antenna module like I saw on some pics. I do have a little black box (maybe 1"X1"X3") stuck in the driver top corner of the rear window. Under the panel are just 2 connectors, one for the antenna (coax or wathever you call it) and the other one are for the 2 power wires (green for the defrost and white for the antenna) with I believe a little capacitor between those last 2 wires .

 

That's because you got the wrong one. I found this old thread after my 04 Impala defroster quit working. The tab's are good and the grid looked good the back glass is tinted. The switch lit and made the relay click but didn't defog. I found this post and took apart the fuse panel to get to the back of it for the circuit breaker. You can also save yourself some time by just squeezing the sides of the glove box in the back and letting it drop down, then remove the 6 screws and take it off the door rather then taking the bottom dash cover off and then the whole glovebox door. I was able to just take out the bolt holding the panel in and pull it out enough to get the breaker out without taking apart the whole panel.

I switched the power seat one with the defog one(I dunno why it has it I have manual seats)and this morning tried it out and back window defrosted. After doing some quick research the right 30a breaker is part #MNB30 at Oreilly. It's called a MINI circuit breaker but same size as regular 30a one but the blades are narrower.

 

Thanks for the part info!! I went to two different stores near me, I could not find a fuse with the right blades and even asked the clerk.... The large blades I had to modify was the best I could get. I'm going to add that number to the write up

 

All they had to do was pull out their fuse catolog and see there is a few different type 30A circuit breakers, but that would be too easy for them! I dunno where they get parts people from these days, that's why I always do my research online and find what part I need before I go in! Either way just glad it works now.

 

My Monte Carlo is now 10 years old. I want to thank the author for the step by step guide to fix/troubleshoot the rear defroster. My only question is-should I let the dealership handle this or can I bring it to my regular mechanic?

 

"If you are going through Hell, keep going"~Winston Churchill

 

If you believe it's that circuit breaker, anyone competent to wrench on a car should be able to handle the steps outlined.