joelgarcia707

Three weeks ago while driving through mendocino county in my 88 runner, my alternator went out. I ended up spending my Friday night getting towed back to Forestville . A quick trip to NAPA and $140 later, I slapped in a fresh rebuilt alternator. Good as new. Drove her back to Sacramento and my 15 amp engine fuse blows. Gauges quit working, no turn signals, and back window stuck in the down position. No big deal, threw a fuse in and made it back home. She ran good for about a week or so and same thing happens as if the alternator was bad. Got the alternator tested the next morning, FAILED. So another new alternator in and it won't run. Looked up a few wiring diagrams and sure enough your alternator depends on that 15 amp engine fuse to work properly. Still doesn't explain why NAPA sold me a bad alternator but that's not the point. It took me a week to track down the short in that circuit and it turned out to be a short in the wiring to my reverse light switch. Usually the wiring is covered in dirt and oil so it's kinda hard to see the conductor exposed to an electrical ground. So moral of the story? check that fuse if you're having the same problem on your rig, and check those wires from your reverse light switch. And don't buy NAPA alternators. Keep it white!

Terrys87

iTrader: (1)

Hello joel..good post. I remember going thru the same thing and didnt find a lot of information on the engine fuse when I was looking. Mine had rubbed against the tranny and the protective sleeve had kept me from seeing it. It rubbed bare where my pointer finger is.

Hope this helps someone else out.

2+2=4Runner

this sounds a lot like my story...the engine fuse blew, gauges went dead along with the blinkers. not sure about the tailgate window not working...mine doesn't work right now anyways. I cleaned up all my grounds, followed wires everywhere! found one rubbed clean wire on the front drivers side blinker, thought that was it, but no luck! i went thru about 30 fuses trying different things and cleaning stuff up, finally i checked the fuel pump harness, and sure enough the ground on the pump was rusty and corroded. I relocated it by putting a new end on it and screwing it into the body right under the fuel pump panel under the rear seat. put a new fuse in, and it worked! fuse didn't blow...6 days later, i was driving to work and the fuse blew...again the gauges went out and no blinkers! I also replaced the alternator with a napa one, maybe thats the problem? IM not sure if that fuse blowing ruined my old alternator because i kept driving it? I'm at my wits end with this problem...gonna check that tranny wiring harness and if thats not it...its going to a garage! I've put at least 6 days into trying to find the issue, where about on the wire was that short?

Terrys87

iTrader: (1)

Mine was about 1/4th inch above the plug where my pointer finger is. It was just a knick and had a very small bare spot. You will need to move the plastic sleeve up and out of the way to see it if that is where your bare wire is at.

On your tailgate, it isnt as bad to work on as you may think. On my 88 runner build on page 8 and post 185 and 186 is how I got mine working. If you want to by pass all of the safety, I have a ground wire trick that makes the backgate so much more easier. For some reason you have to ground it to the front mounting tab of your center console.

Clean your switch, and run a battery directly to your motor and make sure it works. If those two are working, the only other major thing would be your relay box on the drivers side.

2+2=4Runner

ok, i got myself a multimeter...still trying to figure that one out, but getting there. i checked out those wires, i unhooked them and put a new fuse in and it didn't blow! it has to be on those wires somewhere, are they only for the reverse lights? not sure why, but when i unhooked them, oil dripped out of the plastic harness...is it a possibility that the oil is acting as a conductor and grounding those wires out? I will be checking out your build page for the tailgate stuff...i have actually looked at that one for a few other things...very informative! thank you!

Terrys87

iTrader: (1)

As far as I know they are for just the reverse lights, but mine would blow cruising down the highway so I would say there is power to it at all times. I would guess oil can be conductive, but if the insulation is intact, it wouldnt.

I can use a multimeter, but I know some are not quite sure on using a meter, so I tried to write it up where the steps can be done without a meter for the backhatch. Appreciate the compliment on my write ups. I remember not knowing how to get around in these trucks so tried to make it a little easier for someone else in the same shoes I was in. May not be the best write ups, but hope to get the idea across.

2+2=4Runner

there shouldn't be any harm in leaving it unplugged for a little while, right? i just kind of want to see what happens...if it blows or not...but i just don't want to make things worse by leaving it unplugged.

Terrys87

iTrader: (1)

It shouldnt hurt anything. I would wrap it with electical tape and secure it real good so it isnt flopping around.

Hadmatt54

It might not be your wiring at all, it could be the reverse switch in the tranny. I had one go bad a year or so ago. Normally it is a simple on off switch but mine was going to ground when it was making when the transmission was shifted into reverse. Unplug the switch for awhile, if the problem goes away you know it is not wiring.

About alternators...when the key is the run or start position and the engine isn't running your alternator light and your brake light are both on, if you have access to the wiring diagrams, here's how it works. The brake light is only supposed to be on when either your emergency brake is on or your fluid is low in the master cylinder...so what's going on? The alternator light is fed from the brake light circuit through a diode to the alternator. When the alternator isn't charging it is a dead short to ground, so the brake light and the alternator both light up. The alternator requires an exciter voltage/current in order to start charging, this is provided by means of this alt/brake light circuit which is fed from the 15A engine fuse. Once the engine is started and the alternator is turning because it is excited it will start charging against the feed from the alt/brake light circuit, but because there is a diode in the circuit, the alt cannot back feed this circuit and because the alt is now charging there is no path to ground for the alt/ brake light circuit and the lights go out.
I wouldn't be too hard on NAPA alternators, if you run any alternator without an exciter voltage/current you are eventually going to destroy it.

22R4X4

Would anyone know why the alternator isnt charging but the fuse for it is still good? Every fuse is good but I checked the connections with a test light but it wont turn on. Someone help me out I have to charge the battery weekly at autozone weekly due to the alternator.

rubronthroad

check your alternator

bryy

Old thread But Just want to stress if anyone has this problem to check the area the OP shows in his picture. Same thing happened to me this morning after checking my transmission fluid level. Spent several hours and fuses until I stumbled on this thread and sure enough rubbed bare.

Rachael

I have a problem with my 83 cruiser I was driving home and for some reason the engine died, I looked at the fuses and noticed that the engine fuse had blown so I replaced it and it blew again just when I tried to start it, I have had the, I was wondering where to start looking for the problem, it's a 2h motor with a 12v system in it

wyoming9

iTrader: (1)

Hi !!

Welcome!!

If your engine fuse opens when cranking look at the starting circuit.

What ever other circuits that fuse protects

Never having seen that engine or the EWD`s I am not much help

helidriver

Having the same problem with the engine fuse blowing over and over. Will start and drive but doesnt charge, no dash guages except gas and speed. All engine/bat/starter grounds are tight....?

helidriver

Just going through my account and relized I I fixed this one. My reverse sensor leads from the tranny were sitting on the exhaust and melted shorting almost at the tranny case. Got the wires seperated and taped up and tied up off the exahust pipe. That fixed the dash/charging problem. If it helps anyone.......

steverich12

From other posts I have been troubleshooting these three items on my 4WD 1984/5 4Runner with 22RE engine:
Charge lite is on
No backup lights
No turn signals(hazards work)
I have isolated (unplugged) all wires to the transmission, rear of truck and every connector I can find on the entire vehicle(seriously) except the ignition wires on the steering column (I unplugged the turn signal wires).
From the schematics I found for a 1986 4 Runner the engine fuse (15A) should be isolated with all this disconnected yet when I install a fuse and turn the key on, the fuse blows.

This tells me per the schematics that the red wire on the engine fuse has a path to ground (yes I pulled the fuse block and confirmed) even with every connector save one disconnected.

Unfortunately the red wire leaves the fuse block and heads into the harness which disappears behind the dash. I don't want to pull the dash. I see the connectors that heads to the transmission(neutral and reverse) as well as all wires going the rear of the 4Runner. Again, with every connector on the vehicle is disconnected the engine fuse blows. The short appears to be between the fuse block.and the first connector.??????

Any Ideas? are there better schematics available that would show the next junction of the red wire leaving the fuse block?

Help !!