This is a continuation of a previous thread. I've since received the factory manual with good wiring diagrams, but it doesn't help finding the wire junctions as I try to track down and isolate the sub-circuits.

In my car the "engine" fuze keeps blowing. This is in the fuze box under left side of dash, 2nd column from right, 3rd fuze down. Looking at the wiring diagram, this circuit supplies the combination guages in the dash, the turn signal, the backup light, and the voltage regulator(charging system doesn't charge when this fuze is blown).

There is one red wire coming from the fuze that somehow goes to all these different end points. I'm trying to find the junctions from the red wire (ie...to the combination gauges the wire is yellow) where these different sub-circuits branch off so I can unplug each sub-circuit as I try to isolate the problem.

I've followed the red wire through the left side firewall and under the left fender and into the engine compartment and , I think, to the voltage regulator. But for the life of me I can't see where this wire connects to the other sub-circuits, although I do see a yellow wire but I don't see where it connects into the red wire circuit.

Is there anyone who's followed this type of problem before who could show me where to look for these junction points, or tell me how this red wire ends up at the sub-circuits I've mentioned.

So far I've unplugged the wires at the backup light switch, and also undone the plugs on the left side of the engine compartment near the voltage regulator. The problem is still there as show by a lit test light attached to both sides of the "engine" fuze receptacle(one side is hot from the ignition key, the other side if this infamous red wire i keep referring to).

I'm hoping I won't have to dismantle the dash but I seem to be headed in that direction. This is my first Toyota, most cars I've worked on have logical junctions where wires meet at connectors and it's easy to trace and unplug the circuits. So far this car seems to different. Any suggestions out there?

John

I would start with the steering column. The red wire goes to the turn signal switch. After looking at the wiring diagrams for your truck, I believe you are going to find the junctions you are looking for on the driver side of the dash. You may be able to access by removing the lower panels under the dash and the steering wheel cowel. Since you mentioned that the problem has corrected itself in the past leads me to believe that a wire in the circuit may be pinched or have the insulation worn off. This means you are going to have touch every inch of the wire in the circuit. Especially in places where the wire is next to moving parts or goes through places like the firewall. I had a similar problem with one of my cars. I found a wire that had been pinched between to pieces of metal during a repair and it took over a year for the insulation to wear and cause a problem. It took several hours to find the location of the short.
Being patient and methodical is the only real advice I can give. You'll find it.

KimMg, thanks for the ideas. The problem is persistent now, the previous owner said that it corrected itself but I haven't been so lucky.

Have you ever tried a short circuit detector? I'm wondering if they work as claimed, might help for wires that are hard to get to.

Never used one for a car. Too many sneaks. I have used one for checking telecommunications wiring, and it worked well.

What are sneaks? ("too many sneaks").

Sneaks are when power from one circuit will energize another circuit. Usually through poor grounds.
One example I can remember: I don't remember which American car, leave radio on, turn off car and remove key from ignition, turn on hazard lights and the radio will turn on and off to the time of the flasher.

Here's the solution to my short circuit problem...after isolating and unplugging every circuit I could find without changing the problem, I finally pulled out a clamp type DC amp meter and discovered up to 30 amps running through the system, particularly at the wire from the battery + to the main fuze box, and also on the battery ground strap. The only thing I hadn't checked closely (because unplugging it didn't seem to make a difference) was the external old style voltage regulator.

Found the voltage relay, inside the voltage regulator, had a large tit inbetween the points and there wasn't much movement between the points. Ran the 4 resistence tests on both the v. relay and the v. regulator (both inside the external voltage regulator) and got strange results on the tests for the v. relay. Filed off the tit, got some movement between the points, but the some of the 4 tests were still way off.

Started up the engine and the "engine" fuze was no longer blowing, but the charging system was putting out between 12.5 and 16.2 volts, mostly 15-16+ volts, too high. The amperage was down from the 30 amps but still 8-10 amps and then down to 3-4 amps.

Took the cover off the external voltage regulator and watched the v.relay points while the engine was running...they were sparking all the time, I don't know if that's normal or not but it didn't seem right.

Ordered a IC type voltage regular, about 1/3 the price of the old style external voltage regulator, installed it...problem seems to be solved. Charging system running about 13.5-14.2 volts, around 3 amps at idle depending on whats turned on. More to the point the voltage is staying in that range and not variable like it was.

End of saga...next time I'll remember I have this great Fluke AC-DC clamp type induction ammeter and use it first.

Thanks everyone for all the help and suggestions(over 2 different threads).

John