I am having a problem with my alternator not charging my battery. I was told to check the passenger side firewall and replace the external voltage regulator. I searched the entire passenger fender and firewall. I located the starter solenoid and a red plug, but no voltage regulator. The truck has been running fine for a year. Is it possible that my truck has been running this long without and would installing it help my charging problem


86 f150 xlt lariat
5.0 efi

 

You probably have the 2G alternator that as the internally mounted regulator on the alternator, not the externally mounted one. This alternator has a bad rap, and deserves it. Check the plug that has the two heavy wires coming out of the alternator. This plug likes to melt on these alternators.

 

Something I used to do is when a customer brought in an alternator for this reason is test it, then if it came back good, I'd tell them to re-install the alt, make sure all connections were clean, and bring the car down to test again. By testing it in the car (or truck), you will be testing the wiring and grounds too. A good way to narrow it down a little. Then I can look at things and make suggestions for fixing. Helped a bunch of people by doing it that way and got the issues resolved.

 

On my '83, the alternator voltage regulator is right beside the battery on the fender. Corrosion under the two mounting bolts for the regulator can cause bad charging issues.

Is your alternator original? Brushes in the unit do wear out.

 

According to my shop manual all '86 models have the voltage regulator internal to the alternator.
Have you taken voltage readings at the battery? Should be ~14 volts or so when charging.

The red plug is probably the self diagnostic / code reader port (OBD-I).
http://img818.imageshack.us/img818/4334/obdiloc.jpg

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On an 80 to 86 F-series:

Voltage regulator under the solenoid: 1st generation alternator.

Voltage regulator inside the alternator: 2nd generation alternator.

The 2nd generation alternators are prone to fires.

For this reason, people upgrade to the 3rd generation alternator, which puts out a higher amperage and features an internal voltage regulator and isn't prone to fires.

If you suspect the charging system is bad, I'd pull the alternator and have it tested.

However, if the voltage regulator is bad or just the alternator is bad, replace both of them at the same time. Usually if one has gone out the other isn't far behind.

I'll be replacing my alternator and voltage regulator here soon. I'm tired of the burnt out diode sapping my battery while the truck sits.

Sounds like a new alternator is in the works for you.

 

My 86 Ranger had one of these 2G alternators on it. It now has a 86 Monte Carlo 100 amp alternator on it. A modified bracket, swapping pulleys, and drilling out one of the holes on the GM alternator is what it took.

 

I am rewiring half of my electrical system in my 72 Ford f100. I need all the info that I can get on how to wire my external VR with an electronic ignition that is already installed in my truck? I can't figure out how to combine the two. The person I bought the truck from just ran the electronic ignition straight to the alternator that did not have a built in VR & ran a red wire to the battery in which caused the battery to almost explode on me. Luckily I made it home safely with my pregnant wife. Unfortunately we do not talk to this individual any longer. Now I'm trying to undo this mess & have all the wires connected properly. I've already purchased the correct alternator, external VR, the harness that goes to the VR & battery. The new harness does not seem to be the correct one compared to the original one that I picked up from a scrap yard due to the colored wires. The new VR There is a green wire(I) next to 2 yellow wires(A) then 2 white wires(S) next to 1 black wire(F). I do not know how to put photos up on the threads. If anyone could give me some info that I could pass this knowledge on to someone else in my situation later in life would be a Godsend.

 

Here's a diagram. The second yellow wire on the "A" on your truck is for a noise capacitor that keeps the noise down going to the radio. It's the round silver thing you might have seen in your wiring adventures.

On our later trucks the field wire is a different color. Doesn't matter as long as you hook it up correctly.

 

1963/81: The external alternator regulator has points. In 1982, FoMoCo replaced it with a solid state alternator regulator that has MOTORCRAFT embossed on its cover.

The alternator wiring harness plug is the same, so there's no modifications required.

 

I have a Street Fire electronic ignition(CDI.MULTI SPARK IGNITION PN 5520) that is already installed. Do I need to install my external Voltage regulator without connecting any wires from my electronic ignition? So the Voltage regulator would be wired separately?

 

The charging system is separate from the ignition system.
IOW yes, your charging system needs to be regulated no matter the ignition system.