1998 Chevy Cavalier [yeah I know]

[TRDejaVu]

It's my Son's and I have 2 weeks to fix his rear defroster before he goes back to college and winter in NW PA.

It is getting 1.54V at the heater grid. I tried different ground paths, but always 1.54V. I tried to get to the dashboard switch to check the voltage there, but unless I take the top crash pad off (and passenger airbag), then I can't get to the bolts that let me remove the front trim panel.

Any ideas from the GM-ites on what this might be?

 

[Mickey Richaud]

Any way to check voltage at the grid itself? My first thought would be broken grid wire...

Can you disconnect the grid from the power source and check continuity of the grid?

 

[TRDejaVu]

Thanks Mickey. 1.54V coming from the grid power wire and also at any point across the grid. I'm thinking that there should be 12V coming into the grid.

 

[Mickey Richaud]

Yeah, you'd think it should be 12 volts. But if there's a compromised wire in the grid, I'm wondering if the circuit itself would be compromised.

Grabbin' at straws here...

 

[Banjo]

The feed wire should be full voltage, and touching a test probe across the grid wires should give a progressivly lower reading until you have 0 volts on the ground side.
Having a broken wire in the grid just renders that wire inoperative. The rest should work fine.
Possibly a poor contact in the switch, or a bad connection somewhere upstream.
If you can, test the voltage where it comes out of the switch. That will tell you if the bad spot is before or after there.
With the tester, keep breaking the circuit into smaller and smaller parts till you find out where the issue is.
Best of luck.

 

[TRDejaVu]

I had tried getting to the back of the switch, but they built the whole car around it!!! I checked that I had 12V at the fuse; don't know why it wouldn't, but at least I knew. So that left me stumped and in "dang it" mode. I then flicked (can't describe it any other way) at the switch and after 6 months of it not working, the light came on and full power appeared at the grid. I suspect that the switch is on the way out, but for now it works. I have shown him the "flick" should it fail again, so we'll see if we can get another winter out of it.

Thanks for the responses.

 

[mailbox]

By what you have described you are getting a feedback of 1 1/2 volts thru the ground side. I think you are right about the switch.