Need help why Fuse keeps blowing

[RonnieZ]

I just picked up a 2000 F250 the other day. It was having problems starting. I checked the fuses. the fuse box inside the cab had the #3 fuse blown. It is a 20A that does the cigar lighter/data link connector. then under the hood, the fuse box there had the #6 fuse blown. This is a 10A fuse and it says Diesel only-single or dual alternator "A" field, Regulator. i replaced both these fuses and the truck started right up. Turned it on and off a few times and seemed like the problem was fixed.

i went out this morning to start it up, and that 10A fuse was blown again.

the truck is 2 wheel drive with the 6 speed and only has one alternator. it has a new alternator from ford

Does anyone know what could be causing this fuse to keep blowing, or where i should be looking for the problem.