A few Q's about the 379.

Never worked in a truck dealership, but have spent plenty time getting trucks worked on in them.

In between my time driving trucks, I did spend several years as a tech/service manager in a Ford Dealership. You are generally charged a set "diag" fee to diagnose a problem, unless it is something abnormally difficult to find. In my shop, we would go above an beyond to look for the problem, then if it became clear that it was going to take much longer, we would request extra diagnosis time from the vehicle owner.

Wiring problems often fall under the area of "extra diagnosis time".

here is what I would do:

you are dealing with a short somewhere in the wiring. I would trace the wiring myself and look for anywhere that it might be rubbing against metal somewhere. Even if the wiring isn't clearly shorted out, it could rub through the insulation "just enough" to ground out, causing the fuse to blow.

Take your time, and in places where it looks like it might be rubbing through, but you are not sure, move the wiring harness and do something to protect it from where it is rubbing.

 

ok, any place that does repairs needs to charge "diagnostic time", otherwise, the shop would suffer by paying the mechanics hourly wage and not take in any money to pay them..........so that's business. some shops apply the diagnostic charges to any repair that is needed, some shops DO NOT APPLY those charges towards any repair. nuff said about that.

as for you, you can look into the fuse panel, or any place else that there are junction blocks with spaghetti (wires) all around. check to make sure that nothing is loose and touching something else, causing a short circut. for that truck to be a 2006, is it out of warranty...?? you need to check the owners manual for warranty provisions, and time frame cut-off points.