2002 F-250 7.3 wont crank when damp or raining
 

After having the PCM replaced by ford my truck wont crank when damp or raining. My batteries and alternator are good as tested by the dealer and they put a new starter on because they broke the terminal off the old one. I have to unplug the wire under the hood and jump it to the positive post on my battery. the ford dealer told me it was a moisture related problem (no s*#t). IDK what else to check I cut the starter wire to install a remote start (since removed to be installed by a professional at a later date) which caused this whole fiasco requiring me to get a new PCM. I checked the starter wire on the ignition harness and even re-soldered it to ensure it had a good connection. Odd though once he truck is warm after "hot-wiring" it it starts/cranks with no issue. This will be the third straight week my truck has been at the dealer unless you guys have any ideas.

Moved to the 1999 - 2003 7.3L Powerstroke Diesel forum.

Have u tried cranking it in neutral? U may swap relay 307 with one relay 301. I think they are the same and see if the issue changes.

I think when ford was in there swapping the PCM they unbolted the fuse box and loosens the harness that goes to the starter. I heard a definite click and after I got it buttoned up the truck cranked- and it was raining so think I got rid of the gremlin!

What did u do? Swap the relays?

I just unbolted the fuse panel from under the dash and made sure all the connectors on the back were seated firmly and the harness that went to the started clicked when I pushed it in. No swapping of relays required.