Preacher man

1989, Comanche, 4.0, BA 5-speed

I was in the process of selling this Comanche and the battery had gone dead. The potential buyer was going to help me jump-start the truck and when I told him to connect the cables to the dead battery, he reversed the polarity. Big spark, now nothing. I sent him on his way and pushed the truck back into the garage.
I need step-by-step help on how to go about diagnosing and solving the problem so I can get this truck running again.
I have a multimeter and I'm not afraid to use it.
Battery is fully charged now, so let me know what to do.

cruiser54

Look at the fusible links over by the starter relay on the passenger side inner fender. One or more is likely burned.

Preacher man

Looking at the picture, the fusible links will be the single wires plugged in under the "F"?

cruiser54

Not exclusively.

Preacher man

Gotcha. I'm gonna take a picture and post. Maybe you'll tell me what you see?
If they are burned, is it a simple matter to replace, repair?

cruiser54

Replace the burned one(s)

freegdr

Battery could be shorted also.

Preacher man

OK. After examining the fusible links, I couldn't see any that were visibly burned.
I looked at where they were connected as in the picture above.
Where do I go from here?

freegdr

More details on what now nothing entails ?

Preacher man

???

Preacher man

New battery after mishap.

Preacher man

The fact that I'm getting nothing in the way of current tells me the obvious: I have broken current from the battery. I would suspect the fusible links, but not sure how to tell damage other than by visuals. No obvious scorching or other burn-like characteristics. I see no "main" fuse and all the other fuses are visibly good.

fb97xj1

The insulation may or may not discolor when a fusible link goes bad, so its a good idea to check them electrically, to be sure. Check the fusible links at both ends and check for continuity using a meter. If none, replace it.

Preacher man

I think I found my culprit. One of the fusible links feels like it has no wire in it (easily bent and stretched). I plan on replacing the relay as well. Has anyone found these cheaper than $26-$30? Seems high for a relay.

cruiser54

You found it. Relay may be fine...