Rearwindow Defroster

[jad9943]

Does anyone know how to troubleshoot a non working rear window defroster on a 1996 Collector Edition Coupe?:confused

 

[c4cruiser]

Do the outside mirrors heat OK? Or do they not work either? You didn't specify which system you have (manual or C68) so I'll start with the C68 system. Depending on the system and whether or not the mirrors work, the test can be different and there could be a variety of problems.

This is from my 92 service manual for the C68 Climate Control System, so it may be close to the same. Does the defogger light come on in the dash? If it does, With the motor running, connect a test light between the terminals on the lower portion of the hatch struts. Leave the connectors attached to the struts.

Turn the defogger to ON. does the test light go on? If it doesn't, there may be an open circuit on the "hot" side (wire with a color stripe-maybe black/red). If it is OK, check the ground lead (all black wire) for an open circuit.

If the light comes on, check the wires between the top of the struts and the window grid. Look for burnt insulation or broken leads. Also look for any slices or cuts in the window grids.

There is a defogger relay that controls the back window grid and the outside mirror grid. When you press the defogger button a ground signal is sent from the Heat and A/C controller head to the CCM. When this signal is received and ONLY if the engine running, the CCM energizes the defogger relay by grounding the other side of the relay coil. Voltage is the sent thru the circuit to the grids. The CCM will de-engerize the relay after 10 minutes.

You should also check the A/C fuse.

 

[jad9943]

Thanks - I will try this and let you know!

 

[jad9943]

Thanks
Bad fuse!

 

[CKA_Racing]

Does anyone know how to troubleshoot a non working rear window defroster on a 1996 Collector Edition Coupe?:confused

Check the fuse first. A chevy dealership in Tyson Corner in VA worked on mine. Kinda long story but they said they fixed it. BS.
I did not work. I looked it at when i had soem spare time. I found the fuse had blown. The fuse box is located near the battery. It's just one thing you should not over look like said mentioned dealership.

 

[CKA_Racing]

oops , never mind.

 

[JohnnyC]

There is a defogger relay that controls the back window grid and the outside mirror grid. When you press the defogger button a ground signal is sent from the Heat and A/C controller head to the CCM. When this signal is received and ONLY if the engine running, the CCM energizes the defogger relay by grounding the other side of the relay coil. Voltage is the sent thru the circuit to the grids. The CCM will de-engerize the relay after 10 minutes.

I know this is an OLD post, my rear window defroster doesnt work. I've gotten down to the relay(?). I can hear it click when i press the defroster button. But i'm not getting any power to the grid via the connectors at the bottom of the window. The fuse is good. I see no breaks in the lines of the grid.

How can I test the relay? Can i move a working relay (one of the ones next to it) and try?