1986 F150 Alternator Problem - Help!
#1
10-20-2008, 12:37 AM
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1986 F150 Alternator Problem - Help!
I just got my brother a 1986 F-150 with the 5.0L motor. Apparently there's an issue with the wiring harness that plugs into the alternator (the square one). Since it's used, of course the wiring is all f*cked. Someone tried to splice in some new wires without replacing the plug itself (which I understand is the problem). So, I'm looking for confirmation. I put in a new alternator, new battery and new solenoid. Truck runs ok for about 2 mins then goes south and dies. I have a battery/alternator tester hooked up and when it stumbles and dies, I can see that power is no longer reaching the battery from the alternator. I suspect that the alternator plug gets warm/hot and resistance goes up and the truck dies.
It gets even worse if you turn the lights on.
I understand that there is a TSB concerning 1986-1994 F-150s
I'm guessing that if I replace the defective plug (pig tail) that the problem should be resolved.
Give me your opinion.
Also, if you have a part number for the pigtail from AutoZone, O'reilly Auto or Napa, I'd appreciate it.
It gets even worse if you turn the lights on.
I understand that there is a TSB concerning 1986-1994 F-150s
I'm guessing that if I replace the defective plug (pig tail) that the problem should be resolved.
Give me your opinion.
Also, if you have a part number for the pigtail from AutoZone, O'reilly Auto or Napa, I'd appreciate it.
#2
10-20-2008, 09:18 AM
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First off the alternator plug will not cause the engine to die after it is running for two minutes.
With a new battery fully charged and the engine running the engine will run for hours with no problem with no alternator even on the engine.
The alternator just recharges the battery for what was lost during cranking and then maintains the battery charge as you drive offsetting the lights, radio and so on.
As far as the plug goes just go to the auto parts store and ask for a G2 alternator plug. You just splice it in and plug it into the alternator.
It sounds like to me you have the "A" wire wired to the wrong side of the starter solenoid. When the engine starts you just running off the alternator and not the battery. Also the "B" wires are open from the load splice to the solenoid/battery. An engine would only run for about 2 minutes this way and would be worse if you turned on the lights.
If not wired to the wrong side then your fuse link is open at the solenoid.
Do you need a wiring diagram of this circuit?
Do the lights come on when you try turning them on with the engine not running?
With a new battery fully charged and the engine running the engine will run for hours with no problem with no alternator even on the engine.
The alternator just recharges the battery for what was lost during cranking and then maintains the battery charge as you drive offsetting the lights, radio and so on.
As far as the plug goes just go to the auto parts store and ask for a G2 alternator plug. You just splice it in and plug it into the alternator.
It sounds like to me you have the "A" wire wired to the wrong side of the starter solenoid. When the engine starts you just running off the alternator and not the battery. Also the "B" wires are open from the load splice to the solenoid/battery. An engine would only run for about 2 minutes this way and would be worse if you turned on the lights.
If not wired to the wrong side then your fuse link is open at the solenoid.
Do you need a wiring diagram of this circuit?
Do the lights come on when you try turning them on with the engine not running?
#3
10-20-2008, 09:55 AM
Join Date: Nov 2007
Location: Murphy, TX
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First off the alternator plug will not cause the engine to die after it is running for two minutes.
With a new battery fully charged and the engine running the engine will run for hours with no problem with no alternator even on the engine.
The alternator just recharges the battery for what was lost during cranking and then maintains the battery charge as you drive offsetting the lights, radio and so on.
As far as the plug goes just go to the auto parts store and ask for a G2 alternator plug. You just splice it in and plug it into the alternator.
It sounds like to me you have the "A" wire wired to the wrong side of the starter solenoid. When the engine starts you just running off the alternator and not the battery. Also the "B" wires are open from the load splice to the solenoid/battery. An engine would only run for about 2 minutes this way and would be worse if you turned on the lights.
If not wired to the wrong side then your fuse link is open at the solenoid.
Do you need a wiring diagram of this circuit?
Do the lights come on when you try turning them on with the engine not running?
With a new battery fully charged and the engine running the engine will run for hours with no problem with no alternator even on the engine.
The alternator just recharges the battery for what was lost during cranking and then maintains the battery charge as you drive offsetting the lights, radio and so on.
As far as the plug goes just go to the auto parts store and ask for a G2 alternator plug. You just splice it in and plug it into the alternator.
It sounds like to me you have the "A" wire wired to the wrong side of the starter solenoid. When the engine starts you just running off the alternator and not the battery. Also the "B" wires are open from the load splice to the solenoid/battery. An engine would only run for about 2 minutes this way and would be worse if you turned on the lights.
If not wired to the wrong side then your fuse link is open at the solenoid.
Do you need a wiring diagram of this circuit?
Do the lights come on when you try turning them on with the engine not running?
Yes, the lights come on when the engine is not running.
#4
10-20-2008, 11:20 AM
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