I replaced the alternator on my truck (1988 ford f150) almost a year ago.

the first time it suddenly went out ,and drained my battery

It happened again , and the new alternator came with a new harness. I replaced it, and believe I have it hooked up right.

I re-charged the battery, and let the truck run.

the battery is draining with the truck running.

what do you think?

replace the battery,

or something else?

 

Bumping this for you...

Also, it sounds like the there isn't any exciter voltage which if there was, then the alternator would start charging.

I'm not familiar with the '87-91 Fords. It also sounds like the fire prone 2G alternator as well.

Perfect time to start researching the 3G swap.

 

I think you have a 2G alternator with the "firestarter" harness.

If you haven't already I'd replace the charge pigtail. (the rectangular plug with two black/orange wires and a white/black wire)

​​​​​​​look up Ford Technical Service Bulletin 96-2-14

 

I changed the pigtail, does it matter which way the 2 black orange stripe wires are connected to the new pigtail?

 

I talked to a guy that owns a service station, and he said he always had the parts shop check the new alternator before he would take it.

I took the one I got the other day back, it was tested, and the machine said it was bad.

I got a replacement yesterday, installed today, but the alternator still isnt charging.

I talked to someone who said to check the battery bolt on the side of the alternator, with a volt meter, and see if the alternator is putting out 14 volts,

if not the alternator is bad, or the harness going to the starter solenoid is bad, or the harness coming out of the truck somewhere is bad,

does this truck have a voltage regulator, or is the starter solenoid on this model trucks also the voltage regulator?

 

I googled the service bulletin and didnt find anything...

 

No. They both splice to a single fusible link before attaching to the starter relay.

Is there continuity through the fusible link?

That's surprising.



As mentioned, do you have power to the light green/red wire with the key in 'run'?
Does the charge failure light in the cluster come on when you first turn the key?
(because the lamp is the source of exciter power for the starter)
​​​​​​​If no light, check the fuse.

 

The 2G alternator has a charge plug, not a charge cable attached to a stud on the back.

2G's have the voltage regulator attached to the back of them.
​​​​​​​Do you see where it says "ground here to test"?

​​​​​​​The fender mounted starter relay has nothing to do with regulating the alternator output.

 

Not sure what the charge failure light looks like on the dash,

the rear anti lock light lights for a second, and then check engine light comes on for a second, and the brake light is on.

I've checked my fuses in the dash (I will recheck them again). are there any fuses anywhere else?

 

the only fuse that doesnt work is the 5 amp fuse going to the lights,

I can remove the fuse, and turn the lights on, and touch the test light to the fuse box that holds the fuse,

but when I put the fuse in, with the lights on, the test light wont light.

 

You need to test the grn/red wire to ground (-) for any kind of indication of it being hot in run.


Charge failure is a little battery symbol on my '87 cluster.
I dont have an '88 EVTM to confirm that yours is wired the same as mine.

 

I turned the key on to run,

negative battery post, hooked to test light,

touched the green/red wire with the test light, and it didnt light up.

 

That is how my '88 is.

 

the battery light doesnt come on with the key on, or when the truck is started.

 

The battery light goes off when the alternator starts turning and producing power.

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