Fuse 15 Blowing! (Alternator)

[ttbit]

I am trying to resurrect a 96 Explorer 5.0 that had been sitting for 3 years. I replaced the fuel pump and got it started the other day. No charging from the alt, so I took it in and had it rebuilt. Still no go. Checked fuse 15 and it was blown. Everytime I turn the key on, the fuse blows. Checking it, one side shows 12v on key on, the other is shorted to chassis ground by the fuse box. I am thinking the other side should not show shorted to ground and maybe that is my problem? According to the autozone schematic, this should go to a charge warning indicator where as the other side goes to 12v at the key.

Any suggestions here? It could be anything with this vehicle. I found the MAF wires a little mangled and fixed those. At least it does run!

Thank you,
Don

 

[BrooklynBay]

What else is protected by this fuse?

 

[budwich]

"shorted by chassis ground by the fuse box".... if you mean there is a ground physically there (ie. wire, strap, etc), then you are right with "it shouldn't be there". The other side of the fuse runs to the instrument panel.... and should power your "charge lamp" AND your air bag light.

 

[ttbit]

Whoa...you guys are quick. Sorry, what I meant by "short" was by checking one lead of my Fluke meter to the bolt holding the dash up and the other on one side of the fuse socket, I get less than an ohm of resistance. I assume that is a good chassis ground. I don't remember seeing the battery light or ABS light, come to think of it. I do remember seeing the check gauges light, and my battery gauge reading low.

So you think it might be the wire shorting to ground somewhere then? I am not sure what all is on that circuit. I don't have the complete schematics. Maybe I need to pull the gauge cluster first?

Thank you,
Don

 

[BrooklynBay]

Could you post the Autozone schematic?

 

[ttbit]

Could you post the Autozone schematic?

Don't laugh... It's not much!

http://mywebpages.comcast.net/dperuski/exp.gif

When I inserted it as an image, it was huge. I better stick to the link.

 

[BrooklynBay]

 

[BrooklynBay]

Check the charge light, and the resistor. If the light is blown out, and the resistor is shorted, then the fuse would get a full ground connection on one side while it gets a positive voltage on the other side.

 

[ttbit]

I'll see what I can find and report back. I figured the resistor was in there in case the bulb blew out to keep the 12v active to the regulator. Thanks for looking!

 

[ttbit]

OK...update. The lg/r wire is fine from the dash to the regulator connector and is not shorted to ground. The yellow wire is, however. Tracing it back to the fuse box on the drivers side dash panel I see there are two yellow wires spliced together where one of them may go to the engine compartment! Where the heck does that second yellow wire go? The schematic shows one yellow coming from the fuse to the lamp but not the other one. I haven't cut it yet, but I'll bet that second yellow wire is causing my problems as the one in the dash can be moved by tugging and the short to ground does not change.

You gotta love how they just spliced into the circuit like that.

 

[BrooklynBay]

The yellow wire shouldn't be grounded if there is no ground coming from the light green/red wire. Somebody tried to add an ignition controlled accessory in the engine compartment which is shorted to the ground of the vehicle.

 

[ttbit]

The yellow wire shouldn't be grounded if there is no ground coming from the light green/red wire.

Exactly! I believe this is my entire problem. I can't find where that second yellow wire goes though. I may have to untape the whole harness unless someone can lead me to an area it may go to. Heck, if one yellow wire is as important as getting the charging circuit going, I wonder what the other yellow wire does.

 

[BrooklynBay]

You shouldn't have a yellow wire going into the engine compartment. The light green/red wire should go to the regulator.

 

[budwich]

the circuit diagram shows two "runs" of yellow so your problem isn't that there is two... your problem is that one of the runs is bad or has "some bad things" on it. One of the runs is for your IP while the other is for the air bag system.

I wouldn't be afraid to cut a splice and re-splice if necessary to isolate your problem... from there it will be easy to figure out which side of the two runs of the splice are giving you problem.... my bet is the IP run has a short at the panel / connector.

 

[ttbit]

Budwich: Do you have a copy of that diagram you could send me? I ordered a CD last night that should have everything, but that might get me started as it will be some days before I get the CD.

I know the two wires are factory and one of the circuits is bad. I hate to unravel all this wire if I can help it. I will cut the wire that is easiest and re-measure resistance. I do have an electronics background and was a tech for many years. I actually enjoy this stuff, although it is all about having the proper tools and the wiring diagram would be an important one. I pulled out my 2001 Ford manual and noticed they routed two different circuits off that wire in the Mustang too, although it doesn't help me here.

I appreciate the quick and helpful responses.

 

[budwich]

well there really isn't much on it (the picture). I have to figure out how to post it like above. To help reduce your cutting, you can track down your air bag monitor... its on the right hand side (passenger) dash... somewhere underneath but I don't know what you are looking for and whether it is accessible easily. Both wires ultimately go there... pulling the connector and testing will tell if the problem is at the instrument panel (which is in between) or at the monitor module. I would still do a cut but cut wisely so you can readily splice back the wire (somewhere where the wire section is really loose). You can PM me with your email and I can email you a "word document" with the picture in it but don't expect much as they are basically two wires coming from fuse 15, one going thru the instrument panel (light) to the monitor "box" and the other going straight to the monitor "box"... that's it. One thing though when you play with air bags... disconnect batteries for 15 minute just to be safe so you don't blow your bag and your head.

 

[ttbit]

Solved!

Thanks to Budwich telling me the circuit went to the airbag module, it is now obvious what happened. The air bag module was in the middle of ground zero on this vehicle in the accident. The floorboard is bent up right at the module and it destroyed it and the connectors leaving shorts in it's path. I am very lucky this didn't trigger any kind of airbag deployment while troubleshooting. After bending the floor back as much as I could to get the last bolt out, I removed the module and the yellow wire is now open instead of shorted to ground.

I'll have to decide if the car is still worth repairing. The mangled parts are adding up.

Thanks to all for the help. Great forum!

 

[BrooklynBay]

Thanks for the update!