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-   -   Rear defroster woes (https://forums.turbobricks.com/showthread.php?t=362670)

LeedomtoFreedom 11-06-2021 06:54 PM

Rear defroster woes
 
Getting ends tied before winter hits.

The rear defroster does not seem to work.

Tested with a laser temp gauge and it doesn't show any change. The switch receives and sends power to the relay, the relay clicks and sends out the 12v but the filament doesn't seem to heat up. I can't directly check the filament in the window due to tint.

Need some advice before I can't see.
Thanks

283SD 11-06-2021 11:29 PM

What model?, if it's a wagon, check the wires at the hinges.

LeedomtoFreedom 11-06-2021 11:33 PM

90 240 wagon. I'll check

B3rnard 11-07-2021 11:05 AM

Defrost relay
 
Hi LeedomtoFreedom,

Doing EXACTLY that right now, before winter. Mine's 1991 245, switch is OK, but which relay did you get to? I have 3 behind the console, of which 1 is for the turn signals.
Do you have a part# or pic from the relay in question? Cheers! B.

Hinges checked, did those this summer. Tint film also in the way.

LeedomtoFreedom 11-07-2021 08:03 PM

Quote:

Originally Posted by B3rnard (Post 6228522)
Hi LeedomtoFreedom,

Doing EXACTLY that right now, before winter. Mine's 1991 245, switch is OK, but which relay did you get to? I have 3 behind the console, of which 1 is for the turn signals.
Do you have a part# or pic from the relay in question? Cheers! B.

Hinges checked, did those this summer. Tint film also in the way.

It's in the drivers footwell. Mine's probably in a different location than yours since I did a manual swap and didn't remember where they went. It's not the silver headlight relay. It's a tall white box relay with 4 pins missing a central pin. When you turn the defroster on you can hear it click on.

was looking for some wiring location info since there really isn't anything I've seen.

2 old for this 11-07-2021 08:34 PM

Use a test light to check voltage at the grid and ohm meter for ground at the other side.

dl242gt 11-08-2021 01:29 PM

The Bentley manual has relay locations as does the greenbooks. Try to find a print version of the wiring diagram greenbook for 1990. They are very helpful with this kind of stuff.

LeedomtoFreedom 11-08-2021 06:38 PM

Okay popped off the inside bevel of the hatch window where the cable ends meet the heating element. Getting 12v to the hotside and ~.18 v on the ground side. This seems normal as the heating element is a big resistor. What gives. How long does this thing take to heat up?

283SD 11-08-2021 08:58 PM

From a cold start on my '90 wagon, about a 5 mile drive, by then I was at the shop that I did contract work for.

Lazarus 11-18-2021 12:47 PM

OK, you have determined that battery voltage is getting to the rear connector. Separate the connector (engine off) and check resistance of the heating grid. I'm guessing it should be 1 ohm or less. Typical failure points are where the wires connect to either end of the grid.
-Lazarus


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