Alternator fuse keeps blowing

keefgras · Nov 18, 2015

94 Ranger 2.3 Please HELP! Im desperate, its the number 16 fuse where the yellow and white wire go to alternator and fuse box under hood.It blows as soon as I start the truck. If I unplug the pig tail at the alternator the fuse will still blow. Alternator was just tested and is good. Does the yellow and white wire go anywhere else besides fuse box? I've done all the tests. Any ideals?

RonD · Nov 18, 2015

I show '94 ranger 2.3l have yellow/white stripe alternator wire going to fuse 20(15amp).
1993 ranger used fuse 16 instead

But none the less if fuse blows the yellow wire has a short, it only goes from fuse to alternator

keefgras · Nov 19, 2015

ThankYou Ron!!! It probably is fuse 20, right underneath 16. I'm going to try a new alternator pigtail and cut the yellow wire at alternator and before fuse box and replace it. What do you think?

RonD · Nov 19, 2015

I would first use an OHM meter, remove fuse for yellow wire, remove yellow wire from alternator.
Set ohm meter to 5k or similar OHMs then touch one probe to yellow wire connector and the other probe to Ground, 0 ohms or very low ohms means a short to ground in that wire.
Move wire around and see if you can "break the short", ohms will go up very high or meter will show N/C(no connection).
If you can break the short then start unwrapping harness to get to the short.

The reason you want to do this and not just run another wire is because if one wire in the harness is shorting out then wires near it may be suffering the same fate, i.e. there is a reason that wire shorted, could be too near exhaust or got chewed on by a critter, or...........?? don't know but it would be good to find out why it shorted.

Short could even be in/under fuse box

If you don't have and can't get an OHM meter then use a 12volt test light.
Remove fuse
Remove alternator harness
Hook test light to yellow wire and other end to battery +
Assuming yellow wire is shorted to ground the test light should light up
Move wires around to break the short

keefgras · Nov 19, 2015

I do have a meter. Its raining now and I will test it asap and let you know.I did test it but I tested it with volts DC. It was low. Thanks again.Its raining now and I will test it asap and let you know.

keefgras · Nov 21, 2015

Solved

It worked. I put a new pig tail on alternator and that was my whole problem. There were no cracks or burn marks on it. I almost didn't want to cut and splice it. I figured I try that before I ran a new yellow wire. Thanks RonD!!

RonD · Nov 21, 2015

Good work

Thanks for posting the fix

Alternator fuse keeps blowing

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