I have an electrical problem going on with my 1991 F150. The truck was running fine and then it was dead one morning. Jumped it off, went to work and I noticed that about the time I got to town it was not running right. Looked under the hood and noticed that it smelled and smoked a little, I touched the neutral connected to the frame and it was so hot that it blistered my finger. The whole wiring system was hot. I got it back home later in the day, but haven't driven it since. Anyone have any ideas on what the problem might be or how to find it. There was a fuse that was somewhat melted but the link was still intact.

 

You probably have a bad ground connection on the engine block. The main grounds to check are on the block and the other ground stud mounted next to the battery/starter relay.

 

By neutral I will guess you mean Neg (-) Battery cable.
The lug hooked to the frame should not have any power going to the frame unless you are pulling a trailer or do not have a back bumper.
That cable is to be hooked to the engine block and the frame is optional.

So make sure you have and good ground at the engine block and not the frame.

Make sure you have a good body ground also from the NEG post of the battery to the body with a 10GA wire or bigger.

Edit: I see rla2005 beat me to the post while I was typing.

 

Yes I meant the negative battery cable I'll check that tomorrow.

thanks

 

I was fast on the draw there Bill!

Randy

 

I checked the negative post, it has a good to connection to both the frame and the engine block. I then disconnected the negative battery post and checked between the negative battery post and the negative cable with a volt meter and it read 12V. I then took each fuse out under the dash until I had removed and replaced each one. I continued to get a reading of 12V on my meter. I disconnected each connection to the alternator and still got a reading of 12V. Anyone have an idea as to where to go from here.

 

See if this helps you:

https://www.ford-trucks.com/forums/1...t-need-it.html

 

What you describe is perfectly normal. You are measuring between the source (battery) and ground. Your meter is now acting as the "load" therefore all the voltage is "dropping" across it.

How did you check the "good connection to the engine block"? a visual check will not reveal much. It's the corrosion, contaminants under the connection that cause the problem.

 

In his first post he said the ground cable was hot from the battery to the frame.
Then he said the whole ground battery cable was hot. I do not know if he means just from the battery to the frame or all the way to the engine block.

If he is saying just to the frame then the engine connection is bad. There should not be any current going into the frame at all unless he has a trailer on the truck. The only other way any current will go into the frame is if he does not have a body ground going from the NEG post to the body. Then the current will go into the frame and back through the static braids to the body.

Yes current flows from the NEG post of the battery and tries to get back into the POS post. Sometimes it has to work to do that. This statement is for somebody wondering why I described the current flow above the way I did.

 

So would a poor engine block ground cause the #10 wire from the negative battery cable to the frame to become hot also.

 

Yup!! Sure would as it is trying to do the work of a much bigger cable, that pretty much says your ground to the block is bad....

 

X2

 

That wire goes from the negative battery post to the body and not to the frame.

 

It does go to the body, was trying to remember where it went without looking at it. But a poor engine block ground would affect it the same as it would the negative battery cable.

 

Yes that is true. The lug at the frame would be heating up the cable when you tried to start it.