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AM1 and AM2 fuses blowing


candace

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While driving, our 1984 Toyota Huntsman died (carbureted, manual trans). Found the 30amp AM2 fuse blew as did the 15 amp cig lighter fuse in the panel under the drivers side dash. Replaced the fuse and fuseable link. Searched for a short under the hood. Cleaned up and organized the wires under the hood. Took it ta mechanic. Computer said alternator was fine, and everything else was ok. Did fine for another 80 miles. Then lost all electronics in the cab and the air conditioning. But the engine didn't stop. I was able to make it to a rest stop. Once I turned the ignition off, it would not restart. Found the AM1 fuse was blown and the cig lighter 15amp was blown again. The diagram of the fuse box shows the AM1 fuse is 40 amps but mine was a 60 amp fuse. Used some wire connector and a piece of wire to make a jumper for the fuse. Truck started. Turned AC on, fuse blew again. I have no idea how to troubleshoot from here. Tried to use the fuse jumper i made again, but it sparks really bad when I try to put it on now. I've looked for a shorted wire everywhere...well, everywhere I can think to look. Any advice?

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You got some strange stuff going on there I think the A1 fuse is for the alt. When the isolator is a solid state one (yours is) the alternator has to be rewired so it is no longer stock. The old alt b+ is then connected to terminal 1 or 2 (it does not matter what one) then a new wire is connected to the alt that goes to the "A" terminal on the isolator. I don't understand the coach battery being under the hood where it is either. Bottom line this does not explain your lack of power when the thing is not plugged in either. The fuse being 60 amp instead of 40 is probably because you have AC. It is possible your isolator is toes up but there is no way I can see it from here but that would only explain a discharged coach battery in the coach or truck. The diodes inside of the isolator generally fail open but on a very rare occasion fail to ground so that maybe your short  but I'm only speculating I think you need to find someone nearby that understands RV wiring a 60 amp short should not be real hard to find.

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you have got a pretty serious short somewhere.  I would be REALLY REALLY careful about bypassing those fuses - you could burn that TOY to the ground.

If you change the fuses again, I would leave the AC and everything else you can live without off and see how long it lasts.  Essentially you need a wiring diagram to see what those big fuses do. Also, if you replace the fuses, I would feel fuses to see if they are heating up(getting warm).

 

I also would try to inspect all the wiring harnesses - a rodent can chew thru causing shorts. Also make sure nothing got loose and was burned by exhaust components.

 

When you could not restart, I think that you did not have electricity to operate the starter.  I also suspect that it would have run until the start battery died.

 

 

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1 hour ago, Derek up North said:

Easier said than done. The only decent schematics I've seen are from Winnebago and even there, only as far back as 1990.

This is the 'best' I've ever seen for a Sunrader!

Sunrader Wiring Diagram.pdf

that looks like the cabin , I think a toyota diagram is needed - the base pickup from that  year is where I would start.  The service manuals I have down loaded don't go into wiring.  I googled  ----  1984 toyota pickup wiring diagram  ---   looks like some are available

Edited by DanAatTheCape
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Thanks for your replies. One thing I failed to mention in the original post is that when the 30 amp fuse blew the first time, the positive wire from the fuel pump had become detached from the solenoid that powers it. the nut that holds it on had come loose and was missing. So the wire was hot and loose under the hood. It's hard to believe the blown fuse wasn't related to a hot wire floating around under the hood.

I found an auto electrical specialist who cleaned up the wiring for me and looked for a possible short. He said the wiring that runs over the top of the emergency brake was being rubbed by the brake pull every time I pulled it which could have been the problem. But he also found a loose wire behind the cd player which could have been touching the metal at the back of the cd player. 

After he cleaned up the wiring, I've had no more electrical problems.

But I'm having a problem with combustion. Lot's of backfiring inside the exhaust. Not really loud backfiring, but like crackling pops. Lots of them one after the other. When it's backfiring, the truck is also jolting. It's especially bad when climbing a hill. But if I'm climbing and drop it into first gear, it goes away. Someone told me it could be timing. Idk. Any advice?

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