Hey All,
I have a 1997 F150 XLT 4.6L w/Tow package.

I was pulling my boat over a mountain pass and just as I got to the top the alternator light was glaring on and the gauge showed the voltage pegged (>18 volts?). I didn't want to stop in the middle of no where so i drove another 40 miles to the next town to a NAPA store. We figured the VR gave out so I bought another ALT. and a new battery since the old one smelled cooked. I put them in and drove off no problems, dash lights out. Until I got about an hour down the road the ALT light started flickering and then it was on again. This time the gauge showed correct voltage. I tested the charging system at the battery with a multimeter and with the engine off it shows about 12.6 V and when the engine is running it shows 14.40 and revved it shows 14.45. It seems the charging system is working fine.

My question is there a code or something the ALT light can give off like a CEL? I know there might be a chance the new remanned ALT could be bad or have a loose wire but it works.

I'm planning a road trip half way across the country this summer and would like to get this fixxed before hand. I plan on taking it to an Auto-Electrical place but thought I would try here first. I don't want to be stranded out in the middle of no where again. Thanks!

 

The remanned alt is probably having issues. However, it would not be a bad idea at all to get a professional diagnosis - something else may be causing the alt to do weird things.

 

It could be the remanned altenator but also check the mega fuses and/or fuseable links, one of those could of cooked when the alt went into fry mode....

Mega fuse image>>>https://www.f150online.com/forums/3515041-post13.htmlcourtesy of jbrew

There's also a mini fuse in the alt wire, orange wire then goes to yellow wire on/by fire wall....20 amp mini fuse

 

Thanks for the quick responses guys. I forgot to mention that the dash light is off when ther truck is cold and starts flickering on after about a half hour of driving then it stays on until the truck cools down. I was thinking the same thing on the reman, of course NAPA says different.

As far as the fuse is it both big fuses in the picture?

 

Yes....you'll need a meter to test the continuity across them to verify if they're still good....disconnect your battery before testing....

 

Couldn't see the pic offered above, but check the alternator field fuse I believe it's called. Check your manual for location, but check it.

 

Turned out to be the harness tha plugs into the alternator. Had a weak wire or something that got hot and caused a fault to trip the dashlight. I can't take credit for it Hi-line Auto Electric in Seattle is a great place for finding electrical problems. Didn't charge me too much I'm just glad ithave it fixed.