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Simple electrical Q: Rear defrost on '87 GL Wgn.


jdub
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This is a Hitachi carb'd EA82.

 

Here's the deal: no joy at the rear defrost grid. The grid is in great shape BTW.

 

Relay clicks, lights go on both at switch and on dash, and numbers 17 and 18 15amp fuses look just fine (I believe #12 handles the dash/switch lights).

 

Hooked a multimeter at the rear defrost spade (tried both sides) and to ground, but nothing.

 

Tried several relays, all without success (and all click just fine).

 

Any ideas? Any other fuse or otherwise? The only thing I can think of is a break in the line?

 

I suppose I could check continuity from the fuse to the rear defrost spade(s) but I don't have a set of lines that long!

 

Many thanks in advance for any help you can give.

 

John

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Pull the rear cover off the back door and look for a broken wire on the (left?) side of the hatch.

 

I think it's a fairly common problem where the ground wire heats up and breaks off. It did it on my wife's loyale.

 

IIRC, looking from the rear, the left side is the hot 12v side, and the right side should be ground. You should be able to turn the defroster on and find 12v on one side.

 

side note...

I checked the current draw for the defroster after I fixed it. It was around 5 amps :slobber:

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Not sure if I can pull a/the cover: the electrical lines from the defroster spades, each side, go into the upper steel window surround section of the rear hatch (this is a station wagon) and from there emerge, together as a bundle, at the top of the hatch to disappear into the upper section of the car.

 

That is, it appears to be all metal. Is there an inspection plate on the '87gl that I might use?

 

For the continuity check, I see that I would be checking the circuit from spade to spade: good idea! I guess that'd tell me if the grid was dead, but even if it was wouldn't I be getting some juice from a space-to-ground test?

 

Many thanks!

John

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Listen to hooziewhatsit... if I had seen this first it is exactly what I would suggest. The wagons seem to have a common problem of this connector burning and pulling apart. So far I am 2 for 2 on this problem, and I expect to be 3 for 3 now.

 

The connector is under the large plastic trim panel on the tailgate (like you were going in to check on the lock/latch mechanism) and is secured to a portion of the tailgate near the lock/latch mechanism (near center/center, but off to driver's side a little).

 

After a fuse, this is the next place that I would look.

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When I first bought my 87 gl wagon my rear defrost wasn't working. Upon pulling off the trim panel off the inside of the hatch I discovered most of the wiring was REAL badly melted. When I have the time I'm gonna run some fresh wire , but until then I've pulled the fuse.

 

I actually remember reading a TSB on Alldata about this problem but can't seem to find it now.

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Interesting. My grid works *kinda*. Only the top three wires do any good, so most of the rear window stays fogged up. Gonna go check for broken wires; I never would have thought of that! I wonder if this might be related to/causing some of my other electrical woes.....

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The wire/connector damage that I am talking about really isn't a problem with wire guage... more of a problem with connector and, I believe, tension on the wire. On the latter, I don't think that Subaru allowed enough slack in the line, so there is a little too much tension pulling at the connector and the wire going into the connector (especially as the wire jiggles over bumps), generating a bad electrical connection and resulting in higher than anticipated resistance, resulting in overheating.

 

eponodyne, your problem is probably just the age old one of the electrical traces acoss the glass being broken somewhere. Sometimes when the glass is fogged and the break isn't total, you can see where the break is by looking for a spot of cleared glass on the otherwise nonworking line. Or you can take a volt meter and look for where the voltage disappears/reappears on each trace. As mentioned, you can get conductive-ink pens to fix this problem, and prevent it by not letting cargo, etc, touch the rear glass.

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Incredible!

 

EXACTLY as you say: I pulled the plastic cover panel and found that the groundside wire (driverside) connection was not connected - both ends simply hanging there. Plugged it in and I now have full defrost across all wires.

 

I'll cinch the connection up with some electrical tape to make sure this doesn't happen again. Many, many thanks!!

 

John

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  • 8 months later...

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