So I have learned that there is a antenna defroster module located in the rear interior quater panel but I don't know how to remove the section to access it. Anyone have some instructions on how to get into where this module is please?

 

If it is to solve a non-working re-defroster, make sure before doing this, you checked:
- Tabs properly attached to rear window
- Fuse are good
- Circuit breaker is good (it is hidden on the back side of the passenger side fuse block, you have to remove the glove box to get to it).

If it is good, then to get to that module, if I recall, you need to pop the clothing hook out (it requires a screw driver to slide the plastic keeper out). You *might* need to pull down a piece of trim from around the upper door. Outside of that, the piece just pops off (gentle pull it forward and the spring/pressure tabs should pull out of their slots).

 

I accessed the module but I am not getting any voltage to the plug. At the relay I have 12v I think on the 30 pin and when I press the defrost button I am only getting .5v on the pin below the 30 the other pin across from the 30 has only .5v too. I ohm tested the breaker with a .06 ohm if I recall correctly from last night. I swapped the 2 breakers but still no voltage to the defroster. The antenna/defroster module looks perfect. Any ideas on where to look next?

 

You swapped the breakers? I assume with the one for the heated seats? Even though the ohm test sounds correct, are you certain both breakers work? Such as if you swapped the one with the heated seat, does the heated seat work with the one from the defroster? And we are talking the breaker on the back side of the fuse panel (you have to get by removing the glove box)?

And do you know that the relay is good?

I can see if I can dig up some schematics for it. What year Monte is this (to ensure GM did not have a mid-year change)?

 

Ya I switched the breakers behind the fuse panel. (Dumb place to put them)🤦🏼‍♂️I had another relay of the same part number placed it in but no change. I ohm tested it and seems good, but with the voltage being low on the other terminal points, would that more likely be where the issue might be coming from? I would guess from my little knowledge that if it is not getting the full 12 volts it won't pull the relay over to connect....?
it's a 2001 ss monte carlo

 

Here is the schematic for the rear defrosters.

 

Awesome! Thank you so much!
I do have 12v on the L3 but nothing on the other terminals with the button turned on, am I to have voltage on another terminal?
Sorry I really do suck at fully understanding how power is routed through this relay and how each symbol reads.😑

 

So iam trying to understand where the voltage comes from, is it to switch the relay or bcm to relay?

 

If I am reading the wiring diagram correctly, the power for the rear defroster (what is actually going to the glass) is coming from the junction block under the hood, to the relay, then when the relay is switched to the "on" position, it goes to the circuit breaker, next the antenna module and finally the glass (and connecting to ground on the other side of the glass).

When you press the button on the HVAC controls for the rear defroster to activate the defroster, it will activate the indicator light, it then grounds out the control of the relay (this grounding is what causes the relay to activate and pass voltage to the circuit breaker). But, the other control pin of the relay is getting battery positive voltage from the BCM (looks like the shop book says if the battery is too low, the BCM will not allow battery positive voltage, basically, preventing you from activating the rear defogger).

Checking your path, my thoughts are this:
- you should have 12v on one pin for that relay at all times.
- next check the control pin from the BCM for voltage (should be no voltage with the car off and then voltage with the car on, not sure how much voltage, but I assume it doesn't need much).
- car on, check when you hit the "rear defroster" button on the HVAC controls, does it activate a ground on the other control pin.
- If all the above works, check that the relay is activating and outputting 12v.
- After that, you will need to check the circuit breaker. Is 12v coming in? Is 12v going out?
- Then check if you are getting 12v to that antenna module.
- last is 12v to the connector.

And if all that checks out, inspect the ground pin on the glass, make sure the ground is still good.
I admit, I am not an expert with reading wiring diagrams myself, but I believe that should follow.

 

I will check it out and report back what I found. Thank you!👍🏻