Vasi

Those are the results. The only thing I can think of is that #24 covers a lot of systems, so the main relay doesn't use too many amps. If the short is ahead of #15, then pulling that fuse would stop power from getting there, agreeing with the test results. If the short were before it, pulling the fuse would kill the dash lights but still illuminate the brakes.

Since the short is after the fuse, could the #24 fuse could be energizing through the #15, but not drawing enough power to pop the 10A fuse? And when the fuse is pulled, it cuts the current leaking, for lack of a better term, into the IG1 circuit? I'll check later if the moonroof and wipers work with the key off as is, and with the key off and #15 pulled.

Vasi

So, with the brake switch unplugged and fuse #42 pulled, the brake lights stay off upon connecting the battery.

Turning the key to ON(II) illuminates the brake lights.

Pulling fuse #15, the brake lights turn off. Pulling fuse #24 does nothing. Pulling both turns the lights off.

Curiously, with the key off, #42 in, and #15 out, the charge light goes out and the oil light stays on. Replacing the #15 fuse causes the fuel pump to prime.


Could the horn system be involved in this? I have an aftermarket steering wheel (came installed with the car) and the horn hasn't worked since I've bought it. I never investigated. Problems persist with the horn relay unplugged, but it's also connected to #42 20A.


Finally got the cruise control unit and supporting bracket out this morning. I can't see any clear signs of damage due to abrasion. I'll have to cut the harness cover open to inspect all the wires individually, it's just hard to motivate myself to do it in 10F with a -10F windchill. Any further thoughts?

Former User

I'm wondering whether fuse 24 is blown or its downstream wire has an open.

Click the Test Fuses link in my signature.

Test 1: With all fuses installed, voltage test installed fuse 24 and 15 with the key either in OFF or in ON(II).

Test 2: Repeat Test 1 with only fuse 42 removed.

Post voltage readings for both test tabs of each fuse and in each key position.

Vasi

Batt voltage: 12.1
Fuse #42: 12.0/12.0

_________With #42 in________________With #42 pulled____

-------Key off------------Key on------------Key off------------Key on
Fuse #15: 9.9/9.9-----11.8/11.8----------0.0/0.0-----------11.8/11.8
Fuse #24: 9.9/9.9-----11.8/11.8----------0.0/0.0-----------11.8/11.8

Apologies for the brutal use of dashes in the chart. HT kept formatting out my use of the space key for spacing things.

Former User

Nice data.

With fuse 42 pulled, if you then also remove fuse 15, do the voltage readings at fuse 24 drop to ~0V with the key in ON(II)?

Vasi

And just so I understand this so far, there's a short before the brake switch, which is letting power out of the #42 fuse circuit.

There's a short after the brake switch, which is letting current pass through the rear lights.

Both shorts appear to cross into the IG1 (blk/yel) circuits after the #15 fuse, but before any switches, as evidenced by the dash lights and main relay powering up, and the charge light (which is through #24?) going off upon removal of #15 with #42 in place.

So power could come from the horns circuit, or brake circuit before the switch, then bleed back in anywhere from the cruise control harness, ECU harness, or rear harness.

And because the #42 is feeding the IG1 circuit, and the IG1 circuit is feeding the brake lights, can we assume that the wires melted together at a single spot, possibly where everything would overlap in a harness?

Is that all correct so far?

Vasi

I'll investigate on my next break.

Vasi

With fuse 42 and 15 pulled, and key in ON(II), #24 reads 12.1/12.1.

Replacing #15 reads 11.6/11.6 on both #15 and #24

Former User

I agree, and would also add that the Wht/Grn wire breaks before and after the brake switch are connected/fused, thereby allowing voltage to bypass the brake switch to reach the brake lights.

[edited] I agree.

What switches are you talking about?

This would clearly be the simplest explanation.

The diagram below shows how I currently interpret your test results. Xs are wire breaks, and red lines are abnormal shorts between wires.

If my diagram is correct, it suggests that one problem is possibly a bad dash fuse box.

Vasi

Why would that be the case? If the brake lights don't illuminate with #42 and #15 pulled, but with #24 in place and key in ON(II), there would be power through #24 and into the fuse box, but not the #42 circuit. With #42 in place and #15 pulled, the oil light, etc. illuminate, but the charge light goes out. This would indicate that pulling fuse #15 stops power from energizing the #24 fuse. If the short were before #15, wouldn't pulling the fuse kill the oil light and cause the charge light to remain, as is the case with removing #42 and turning the key to ON(II)?

Hypothetical switches? If the short were in the GRN/BLK wire after the back-up light switch, then the issue would only be with the gear selector in reverse. Since it's full-time it should be between the back-up light switch, and any other switches off that fuse, and the fuse.


I like the diagram, but if the charge light goes off upon removal of #15, then wouldn't that indicate that power is no longer going from #15 circuit to #24?

I've been told before I can come across as rude, so I want to apologize in advance if I come across that way. It's not my intent. I really appreciate your time and experience in helping me out with this.

This is just how I'm interpretting the results, and I'd like to be corrected thoroughly if I'm wrong so I can learn.

Former User

I was editing my post as your were responding. Does my new diagram now align with your thinking and test results? Or is there still an inconsistency?

You can test your before versus after switch ideas by unplugging switches.

No offense whatsoever taken.

Vasi

I'm just not sure what evidence there is for a short in the #24 circuit, based on the results of pulling the #15 fuse with #42 still attached.

Trial and error FTW. I don't see anything in the diagrams that would be on all the time that disconnecting would fix. If it has access to a ground, wouldn't it ground instead of going back up #15 and discharging through #24?