I have a 97 F250 Supercab 4X2, It sat for a little over a year while I was Iraq, now back, I have run into some problems. The battery was dead needless to say, it wouldn't hold a charge. Replacing the battery, being in a hurry, I put the cables on backwards. The horn sounded to let me know this. I put the cables on proper and the truck started right up, but now my battery light on the dash stays on, and my radio won't work. I checked the fuzees under the dash and they all seems to be good. With the truck running, I took the cables off to check the charging and the truck died. So thought to myself, maybe the alternator is bad. But I was able to run for some distance with the dead battery, so I knew that at that time at least the alternator was working. Did i throw some kind of safety switch or fry my alternator? Also I have had an on going problem with the truck running really rough above 40MPH, and idels badly. Before I left for Iraq, it was doing the same thing. The codes then were that I had a bad coil or coils. I pulled them all and checked them and replaced 1, checked the boots and put in new spark plugs. No difference still runs like crap. The check engine light comes on, stays on until the truck warms up and then flashes. I have 100,000 miles on it, could all this running problem be O2 sensors? Any help would be greatly appreciated as I can't afford to have Ford do the work. Ah for the days when you could actually work on your vehicle under the backyard tree.

 

Hi and welcome to the forum

There are 2 fuses for the alternator.....or generator as Ford calls it again, like in the old days.
There is the mega fuse under the black plastic cover on the firewall, near the battery. It's go a black plastic cover over it too. It's a couple inches long. Under the cover are 2 nuts holding it on. You can check it with a test light or voltmeter. It should have power at both ends of it.
There is also a mini inline fuse in between the mega fuse and the alternator.

As for the rough running problem...... Chances are pretty good you have a bad COP (Coil On Plug). I'm assuming you have a 5.4L engine?
After the check engine ligth has flashed there should be a diagnostic trouble code stored in the truck's PCM (Powertrain Control Module). You'll need to get it scanned to find what code caused the check engine light to flash. That code should lead to which cylinder or cylinders the problem is on.
Some parts stores such as Autozone will scan your truck for free. Be careful with their diagnosis though. If you just get the code and post it here we can help you more with it. If it's a P030* code that will show you which cylinder is misfiring and you may want to just replace the COP on that one to see if that solves it. For instance if the code is a P0301 it's cylinder #1 (front passenger's side), a P0307 is #7 cylinder (second from the back on the driver's side).

 

Also, the low voltage will make it run worse, so once you fix that, reset the computer and check the new codes. You say it has 100,000 miles on it, have you ever changed the spark plugs? They are due.

 

Thanks racerguy, it's a start, nope no power to the mega fuze. Will do the code check, didn't know about the free check thanks for that. LXMAN, yes changed the plugs, and replaced one coil. Could any of this be caused by the Mass Flow sensor? Thnaks again.