ford 98 police interceptor p71 pcm fuse #12 keeps blowing
 

I had a bad alternator with blown out rectifiers. Replaced with new one. Problem started as while driving on really bumpy road traction light in dashboard lights and stays on temp warning flashes on and goes off. Check engine flashes on and goes off.Temp guage read normal no overheat. I kept driving like this for 2-3 weeks.

A few days ago engine died. I checked fuse #12 for pcm was blown. With ignition switch in off position there was still a short circuit on fuse socket #12. I removed -Ve battery terminal wait for 5 mins and installed new fuse and drove back home. Next morning I drove to repair shop they hooked it with computer no error code. They said there is a wiring short.
while drive back to another shop engine died again with same fuse blown and persistent short circuit on fuse socket #12 with IG switch in off position. I left it with the shop. Next day they told me short circuit just disappeared while they removing different connectors to check. It was working again with no clue what was wrong.
I drove to work and back home about 15 kilometers. In the night while on shopping trip engine died this time no fuse blown. I just replace fuse to isolate problem and drove back home. I am electronics maintenance engineer not particularly Auto electrician and have digital meter but I am really lost. I am too scared to be stuck on the road. I keep running engine with A/C on while parked switch gear lever to all positions. move and shake every wire I can but simply cannot recreate problem. Any help is very much appreciated.

Traded in police vehicles had to have all sorts of electric features removed. Since it will be someone else's problem ,great care is not always exercised when removing the heavy duty electrical stuff and you may need to find someone with more than average electrical savvy to chase down the problem. Your best bet might be to invest in an amp clamp to pin down any excessive electrical drain.