Heated Rear Window

[Randy in Maine]

Does anyone know right off what kind of resistance I should hopefully be seeing in defroster grids that actually work? I can't find a description of it in the Bentley 4-37.

I have 3 of them and I am getting ready to test them with my ohm meter. I would assume that something less than infinity (around <100 ohms) would be good, eh?

Thank you as always.

[Randy in Maine]

I found a post that a beetle had about 4 ohms in the grid when they worked right. Does that sound about right?

[vwlover77]

Randy, Not sure of the actual specification, but I'd think they'd have wanted to limit the current draw to 10-15 amps.

Since R = V/I and assuming 13 volts and 13 amps for simplicity, the reading would be 1 ohm.

If you compare the readings on all 3 that you have, go with the one with the lowest resistance. Each track is a resistor and resistors in parallel reduce the total circuit resistance. That would be your best assurance that all or most of the tracks are working.

[Randy in Maine]

The window I ended up putting in was about 20 ohms.

[Hippie]

I found a post that a beetle had about 4 ohms in the grid when they worked right. Does that sound about right?

I think that's in the ballpark, yeah.
Newer cars with relays draw more, but shut off after a few minutes automatically....usually.

http://assets.fluke.com/appnotes/automo ... atbook.pdf