well this just started happening, i'll be driving and the gauge that has a battery on it will go down almost into the red area and the headlights will dim as the battery looses power, then it will all the sudden just decide to work again and it will charge the battery. it never happens when i first start it up but after about 5-10 minutes of driving. i thought it was the alternator so i replaced it, it has a built in voltage regulator, next i thought the positive battery cable so while i had it off i decided to replace the battery too and still the problems persist. kinda frusterating. what would cause this to happen? has a new starter solonoid but i cut all the fuel injection crap out of it and it has a holley carb with an electric choke, put the fuel pump on a toggle switch. i did not wrap the wires up that i cut which must be about 20 wires for the fuel injection could one of these be the cause of it? oh it has a HEI dissy with a mallory coil. i have my taillights hooked to a toggle switch from the fuse box. i can't for the life of me figure out what would cause this. the wires going to the alternator look to be fine other than a bit muddy.

oh by the way it's an 89 f-150 4x4 with a 5.0 that has too many mods to list so please any suggestions

 

I'd suggest taking it to Advance auto or Autozone and getting the alternator and battery tested. You can get a lot of good information on the electrical parts from them. They have helped me greatly in the past.

Hunt4Fun

 

1989 was among the years that had a poor electrical connector at the alternator. Many of the auto parts stores sell a replacement pigtail that you should cut the old connector off and SOLDER the new one on to the old wires. Two wires to solder if I remember right. Don't forget to put some shrink wrap over the wires before soldering, or tape the splice good. Hope this helps.

 

thanks i will head over to autozone tomorrow and see if they have that pigtail

 

well i went to autozone (the battery gauge didn't drop the whole drive over there) and got their portable alternator checker thingie hooked up and i played with the wires going into the plugs on the alternator to see if they would be bad but no matter what i did i could not get the thing to stop charging! i figured i was good and maybe it stopped doing it. but...... on the way home i was watching the gauge and it dropped down almost to the red area again and came up for a second then dropped down again then came back up and stayed there for the rest of the trip home. this is really pissing me off, i can't drive at night because i am scared the truck will die

i already replaced the alternator, battery, voltage regulator. and autozone only has one of the alternator plugs and they have to order it....

do you think i should go ahead and get the plug and replace it and see if it still has problems?

 

Did you say that you replaced the battery cables? I've had cables corrode under the insulation and cause similar symptoms, very erratic and unpredictable. Often, the cables seem fine when you look at them. Almost seemed like the resistance only got too high when the engine was warmed up.

Good luck.

 

i have not replaced the negative battery cable but it looks like it is fine. this happened after my parents brought my truck up to college so it was sitting for like 2 months or so maybe i should look into replacing that cable too

 

My dad's 86 f150 4X4 with a 302 had the same problem with intermittent charging. He replaced everything. Its weird but it ended up being a loose ground wire right behind the instrument panel that goes to a metal brace. Tightened that up good and never had problems again. That was like 10 years ago.

 

I quess it would be your call as to when to try that pigtail. That connecter that hooked onto the alternator was a real problem on this vintage of F-series trucks though. I ruined an almost new alternator on my '88 F-150 when that connection melted. NAPA replaced the alternator under warranty and sold me a pigtail connecter. A few years later the alternator quit charging(it was just a problem with the alternator) there was a guy here locally that would repair alternators cheap, charged me about $25.00, he made sure I had already replaced that pigtail or he was going to sell me one.

 

alright i ordered the pigtail yesterday should be here saturday but just for good measure i replaced the negative battery cable too, let me tell you that one is a real b!tch to get to on the block!!!

 

and i just put on the pigtail and the damn thing was fine on the way home till i got to about my dorm and as soon as i turned the wheel....guess what voltage dropped!!!!!!!!!!!
what should i replace next? all the wires that have anything to do with the charging system?

 

I would check the ground wire behind the instrument panel. Seen it do that before. See above.

 

alright i'm gona go out and pull it apart right now hope that's it or maybe it's the voltage regulator plug not the alternator plug or maybe the block to frame wire

 

not the ground behind the gauge cluster i pulled it and could not see anything that looked bad

 

i put a new voltage regulator plug on it and a new ground strap and it's fixed!!!!!!! yay!!!!! i'm so happy thanks guys