We have an 86 4runner 4x4 manual. It is blowing a 15-amp fuse that says engine. The engine will still start and run fine but no dash lights and no charging. We have unhooked everything we can think of and it still blows that fuse. I even bought this electric circuit tester that sends a signal down that wire from the fuse box and a probe is supposed to be able to detect the short. So far it doesn't find it. Wiring diagrams are useless since they are multiple pages and don't show where wires continue from one page to another. Anyone has any ideas i would like to hear them. I hate to junk this thing but may have no choice.

 

Don't junk yet. Ask around to find a shop that specializes in electrical problems. Hopefully you have one. Try Craig's List as some ex-shop/dealer mechanics run mobile businesses out of there. I got a good mechanic to come install a new in the full of gas tank fuel pump for 1/3 the shop labor and I provided the part.

 

My son's truck had a 15 amp fuse that would blow intermittently. It was his O2 sensor wire touching the exhaust pipe on occasion Very frustrating and took a while to figure out. Just a thought. Maybe someone will post the EWD and we could troubleshoot it more accurately.

Good luck. Don't give up.

 

The main function of the Engine fuse is to power the alternator (hence, your battery won't charge).

1. Check the voltage at the battery while running. If less than 13.5v, your alternator is delivering no power.
2. Unplug the 3-conductor connector at the alternator. Using a test light, bridge the Engine fuse. If the test light illuminates, you still have a short (somewhere). If not, you may have a shorted voltage regulator in the alternator. Take the alternator to (just about any) auto store to have it tested. (You use a test light to save going through a whole box of fuses.)

In the '90s, you'd be done, but it appears that in the '80s other circuits were also hung off the Engine fuse (back up lights, turn signals, rear window relay, seat belt buzzer, maybe some other stuff).

Be systematic. Good luck!

 

I remember having a similar issue with dash lights after installing a car stereo. I took that stereo out 3 times to verify the wiring. I turned out to be the light circuit for the tailgate window switch in the console. Probably not it in your case, but I figured I'd put that out there.

 

Well, i think the kids found it. I sent them to the store to get a self-setting fuse. They took parts off and even one front wheel after hearing what sounded like bacon frying behind the wheel. Its somewhere in the harness that goes to the backup light switch from the transmission. With it unhooked, everything works except of course the backup lights. Now to find exactly where the short is. Might just be the switch itself if it uses a hot wire. I would think it would just be a ground switch but who knows.

 

FWIW, my '89 EWD shows the Back-Up Light Sw as hot-side. Fed (as mentioned) by the Engine fuse. If disconnecting the switch at the transmission prevents the fuse from blowing, the short should be on the light side (R or R-L depending on transmission).

 

It was the wires in a wire harness that plugs into the larger engine harness. It was the one plugged into the reverse switch for the backup lights. Those wires are so old and brittle. I guess they got broke from someone messing around back there. He has had the engine out a few times over the years. Can't find that harness and even if we did, it would be old and brittle too. I made a new wire harness just using a little wire sticking out of the plugs to solder to.