Tracking down an electrical issue.

[irox]

Hi svx fans,

I see there are a lot of threads discussing similar electrical issues, I've going threw the different solutions in those, trying to apply it to my problem, but so far, no success.

Car: 1992 LS-L, 47K miles. Just acquired this one a few weeks ago.

Problem symptoms:

- clock isn't on
- AC/Climate panel isn't on
- wing mirrors don't work
- when using an inductive RPM meter, it is very flaky and usual stops working at anything over idle (this means I can't get a California smog check).
- At the Cigar lighter I read 1.016volts
- At the Clock fuse under the hood, I read 10.45volts (hazard fuse reads 12.5volts)
- Fusable link (under hood) reads 10.45volts
- Under-dash Cigar/Mirror fuse reads ~10.4volts

Actions taken:
- sun visors have been disconnected
- cigar lighter has been disconnected

Next actions:
- investigate mirror switches
- disconnect stereo (Clock line also powers stereo memory)
- remove under hood fuse box and test things

I notice the battery doesn't have it's hold down, possibly it has hit the fusebox and/or part of the wiring harness damaging something.

Any input welcome. Otherwise I'll log what I try here in case it helps others in the future.

Thanks,
Ian.

[Blacky]

First of all congratulations on acquiring such a low mileage SVX.
With that low mileage don't rule out the possibility of rodent damage to the wiring. It must have been in storage a large part of it's life.

[irox]

More diagnostics:
- Wing mirror controls and parking light switch appear to be getting 1.1v
- pulling the "light s/w" MB fuse No. 23, causes voltage across fuse No.25 (Clock) to jump from 10.5v to 12v
- Measuring voltage on fuse No. 3 contracts and ground, I get 12.4v on one side and 11v on the otherside (where I expected 0v).

Getting a bit dark to continue diagnosing, will try more later this week or weekend.

I think I'm looking at multiple problems. Drawing out a diagram of the wiring circuits to the components I'm not getting power to, there isn't a convenient single point of failure.

Thanks for the rodent tip. I'll keep an eye for any rodent signs, but so far I've not come across any. From the carfax report, the car was driven a few 1K each year. So doesn't appear to have been parked for too long (multiple years) at a time. Not that rodents needs long to do damage...

[Tireiron]

Also keep an eye out for damaged wire insulation caused by an old accident that may have been repaired. There was one member here who found that before they got the car, the left front fender had been damaged and replaced. From the accident, the insulation on a bunch of the wires behind that fender got damaged and over time slowly corroded and started causing all sorts of intermittent shorting and disconnects. The main power loom runs just behind that fender from the in-engine fuse box to the in-car fuse box.

[irox]

Thanks for the tip. That might actually apply to my other SVX, which was hit on the fender in question before I got it (and has an odd electrical issue now and there).

For this one, I'm starting to suspect the AC control or Clock, since both those are linked to the two fuses I'm see issues with. Which is a bit of a pain, since I don't really want to take the dashboard - at least to just test. Perhaps I can disconnect them without removing the dash.

[Sean486]

Originally Posted by irox

Thanks for the tip. That might actually apply to my other SVX, which was hit on the fender in question before I got it (and has an odd electrical issue now and there).

For this one, I'm starting to suspect the AC control or Clock, since both those are linked to the two fuses I'm see issues with. Which is a bit of a pain, since I don't really want to take the dashboard - at least to just test. Perhaps I can disconnect them without removing the dash.

I believe those come out pretty easily.

[irox]

So, today I removed the radio, clock and AC controls. I'm reading 6v at the clock and AC controls for the output of Fuse No 3.

There is very little left to disconnect on the line, I think it's just the timer module. Tomorrow I'll start checking the cables between the Fuse Box (under dash) and places the No.3 fuse runs to. If that checks out, I'll remove the glove box and get access to the Timer Module.

[oab_au]

All the different voltages you are seeing, could be the result of a ground connection being open.

We will have a few components with there grounds connected together to one line, the Cigarette lighter, Auto Aircon, Clock, and glove box, all use the same ground.
If that ground is open, then these units will get there ground back through the other units, hence why you are getting different voltages.

The best to do is to measure the ground side of these units, to the battery ground, you should always see zero resistance. If you find a resistance, follow that to find where the ground wire is open.

Ps. if you have the manual wiring book, look on page 10.

[irox]

Hi oab_au,

thanks for the tips! I'll be sure to check the grounds.

I've been checking voltage against the harness ground and the chassis ground, both have been giving the same reading, so I was suspecting damage on the live side, either partial breakage in a wire, or a short against something. Something after the Fusebox (fb-12), some where in the harness.

I have the FSM wiring diagram, thanks for the reference, will check that out.

Cheers!
Ian.

[oab_au]

Originally Posted by irox

Hi oab_au,

thanks for the tips! I'll be sure to check the grounds.

I've been checking voltage against the harness ground and the chassis ground, both have been giving the same reading, so I was suspecting damage on the live side, either partial breakage in a wire, or a short against something. Something after the Fusebox (fb-12), some where in the harness.

I have the FSM wiring diagram, thanks for the reference, will check that out.

Cheers!
Ian.

Ian I bummed up that wiring No. its 6.3. diag.16. Ground Distribution.
Sorry.

[irox]

So, it seems it was the Timer Module (hah! the last part in the whole circuit I removed)... With that disconnected, clock, AC, mirrors, etc are all working fine.

Now, to track down a spare, or maybe I'll try to repair the module.

I checked the ground and hot for everything I removed, I didn't see any issues.

[irox]

Oh, some Timer Module repair hints:
http://www.subaru-svx.net/forum/showthread.php?p=747615

[irox]

Well, rats... that didn't solve the problem I'm seeing during the smog check. The inductance RPM meter keeps crapping out (reading 0 rpms) as soon as it goes above idle....