'92 AWD SVX. This car is in great shape, bone stock (including radio, no remote starter or anything), with less than 170k miles on it. Automotive electrical is my specialty...but I'm already questioning whether it's worth it to try to fix this thing, but I still don't want to see another SVX parted out....so I come to you guys. This is going to be a long post, but I don't think there's a good way to give cliff notes without leaving stuff out. So please take some time to read it, and save this car!
Back story, as best as I know. This is a good friend of mine's brother's car. My friend is a car guy as well (worked with him at Autozone, now he's a tech at the local VW dealer, he has an EG33-powered GC), his brother is NOT.
The brother reported that he had noticed a couple things not working. My friend took a look and found a few small fuses blown. Not thinking about it, he replaced them. He's not sure which, or even how many, he replaced before he noticed that the fusible link was popped, and that there were larger issues.
He is out of town this week, and offered to pay me to spend some time on it.
So, when I got there this afternoon, if you put in the stop/horn fuse, the horn would blow continuously, and the cruise/abs and meter/SRS lamp fuses would pop immediately upon ignition on.
I started by trying to find a connection, only connection I could think of was horn, cruise, and airbag....steering wheel. So I pulled the horn fuse to check if the signal wire to the wheel was constantly grounded. Nope, then I realized that all 3 pins on the relay itself had continuity between them, popped the cover off to find the internals visibly melted and shorted between them. OK, horn issue "fixed" (haven't actually put a new relay in...but that's a pretty definitive symptom).
So I start moving on, I decide to go back to square one and treat the other 2 symptoms individually. I start with the fuse, and use the FSM wiring diagrams to trace the circuit through the harness starting at the fuse and narrowing it down to the cause. The remaining 2 fuses both have the same condition. IGN on = 12v at one side, and continuity from the other side to ground.
For anyone that wants to look at the diagrams and see my train of thought, here are my notes. Started with the fuse number, wire color, and circuits. Then went through all the diagrams, looking for that circuit being referenced, and wrote down every plug and pin number, and it's purpose. Then I would trace these, unplug them, and test again, isolating the short.
Quote:
Fuse #15
Meter
SRS Lamp
FB-28 RW
-B41 6. Comination meter power **Short to Ground**
-B9 3. VSS 2
-B87 1, B64 3, B63 1. DRL control unit, relays
-B90 9. Time control unit
FB-29
FB-30 GY
-B39 6. Combination meter power **Short to Ground**
Fuse #18
Cruise
ABS
FB-42 BrR
-B101 6. R7 1. ABS module **short to ground**
-B45 9. cruise switch.
-B86 4. Cruise relay
-B53 16. Power steering unit.
-B35 5. Select monitor.
-B92 5. Security Module
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According to the wiring diagrams, the 2 instrument power wires stay separate until they are within the cluster, but I have not yet pulled the cluster itself to say for sure. I have only tested at the B39/B41 (near the hood release), so there's a foot or so of wiring before the cluster itself, but unless both of these wires are shorted, I think it has to be within the cluster.
Same deal with the ABS unit, I tested at the plug between the bulkhead harness and rear harness just behind the passenger side a-pillar. I don't think I can get to the unit itself without pulling the passenger seat, so again, there's a foot or so of wire that might be the cause, but I'm inclined to suspect it's the unit itself.
Anyway, does anyone see anything I may have missed? My other concern is what might have caused these 3 very separate circuits to be so heavily damaged. What's the likelyhood that these things will be damaged again? I can easily grab a horn relay and ABS module from my parts SVX, but the gauge cluster sold early, so I think I might try to repair this one. But I'd hate to put another few hours or more into this car to have it happen again.