I have a '90 Toyota Odyssey RV. It is basically a 1 ton C&C for this discussion.

A few months back it had a weird electrical problem.

As I was pulling it up from the yard to the driveway, everything went dead as a doornail. The engine quit and everything on the dash, including the radio went black. The only thing that was still live was the headlights, emergency flashers (not the turn signals) and the key in the ignition door open buzzer. I checked all the grounds that I could. I redid the one on the block (large cable) and the smaller one inside the fender, next to the battery.

The only thing I found wrong under the hood, was that the coach electrical
isolator had come loose from its mount and the 12V post seems to have contacted a grounded cable housing. There is evidence of an arc there. The initial problem did happen as I went over a bump which could have caused it. It did not blow any fuses. The coach isolator is the gadget that isolates the engine electrical from the coach electrical when the engine is off. This keeps you from killing your engine battery while parked using the coach lighting.

Anyway, a few days later, it healed itself....sort of. It started and all the
lights returned. Then a week or so later, I went to start it again and a different set of symptoms occured. I have dash lights, but, it won't start. When I attempt to start, the radio goes out and other dash lights dim, telling me that a switch is making and it is trying, but, it won't turn over. Not so much as a solenoid click. Attempting to start with it in D results in no light dimming and the radio stays on. This tells me that the tranny starter lockout switch is functioning. I crawled underneath and ran a wire directly to the solenoid and it starts fine. I was to the point where I was ready to say to hell with it and run a starter button directly to the starter.

So, yesterday, I am poking around under the dash, looking for a good 12V source for my starter button. I was going to use the cigarette lighter. I pushed the lighter in to confirm it was hot. When I did this, the radio went dark. It does this, engine off, but, not running.

Then the everything goes black on the dash symptom came back.

I just know that somewhere I have either a 12V or ground current flow issue. The Haynes schematic tells whats going on electrically, but does not list actual physical locations of all grounds. Does anyone have this info or any suggestions?

I am about ready to throw in the towel and bring it to the garage.

 

It sounds like the Alternater fuse is blown and you drained the battery.

 

I would guess your running at least 2 batteries .

Have you tested your battery isolator ?? Don`t both batteries connect to this.

Do you know is it solid state or mechanical.

If the contacts are pitted it will not be able to draw the voltage needed to start.

I would look there for your problem.

When you hot wired the truck I would guess you energized the solenoid.

 

you sir, are a smart dude, in matters related to toy electrical systems, anyhoo.

The 80A fuse located in the electrical box right behind the alternator was bad. I suspected this in the beginning, but, being a lazy dumbass, I did not take it out to measure it. I measured it in circuit. And, of course measuring components in circuit is dumb as their are parallel paths which will fool you. Being an electronics tech for nearly 30 years, I should have known better.

The thing that puzzles me is the intermittent gremlins I had. You would expect a blown 80A fuse would pretty much kill everything, all the time. But, it didn't.

Time to go camping! Thanks for your replies.