82 targa defogger - with video!

[universeman]

Hi all,

I'm troubleshooting my 82 SC targa rear defogger. Switch works, relay works, power from relay to connector works, and I get power to the driver side of the targa window.

Heated mirrors *seem* to work (albeit slowly) so I know the circuit is good.

However, no heat at all from the defogger means no defogging or defrosting. Well it could be weak weak heat but regardless I get no love and can't see out of my targa window on cold mornings.

I took a video of what's going on as I move my trouble light around, maybe that will help others. Bottom line I get power on driver side, but nothing on passenger side. Anyone know what else I should look for? I don't think it's a ground issue or else I wouldn't have power on that driver side. I'm afraid it's lack of continuity in the wires.

Thoughts?

Video:
https://www.youtube.com/watch?v=UndYmazbQUI

[Dave Colangelo]

If I am correct on how it works your signal light will show nothing on the passenger side as that is ground (0V). Basically the little strips act like resistors (used as heating coils), +12V is applied to them and the power dissipated across them is turned into heat warming the glass up. I would get a good ammeter and see what kind of draw you are getting on the drivers side. I don't know what kind of draw you should be getting but someone here can help with that (mine does not work either, or I would test it for you). You may have a short somewhere along the way that is preventing it from driving the defogger as it should.

Regards
Dave

[RSBob]

Look very carefully at you defrost wires and look for tiny gaps or light spots. If you find either or both of those your current isn't reaching ground and hence no warm wires

[wwest]

One side is GROUNDED! Heat is not enough to feel, and it takes a long time to defog a foggy rear window, even longer to defrost. An actual DMM, HF even, would be better. One of the 3 fuses in the engine compartment provides power, remove it and measure current flow across the fuse contacts.

[universeman]

Very helpful stuff guys, thanks! Will try the above. wwest, what's an HF?

[DaveMcKenz]

HF = Harbor Freight
Dave