Alternator not charging

Alt is not charging. Took it out. Brought to parts store for test. Said tested good. I put it back n to do my own testing. I didn't find anything wrong. But still not charging. I did not get battery tested. But it starts up b2 just fine. Battery has 12.47 volts and only 11.something while running. I've checked my grounds n such. What else to check? Any Fuse able links that work on the charging system? I took the alt back off. And will b getting it tested at a diff store. But if pass. Idk what to do next? This is on an 86 2.9.

Thanks

1986 should have alternator with built-in voltage regulator

There will be one(sometimes 2) larger wires on alternators B+ terminal on the back or side, the one with the nut.
Then a 3 wire connector plugged in to the voltage regulator section of alternator.

With alternator hooked up, Key off
B+ terminal should have 12.47volts(your previous/current battery voltage)
If not then a 60amp fuse or Fusible link is blown.

Remove 3 wire connector
The Yellow wire should also have Battery Voltage, if not then a fuse or fusible link is blown.

Check the Light Green wire now as well(same connector) it should not have voltage
Now turn on the key and test green wire again, it should now have Battery voltage.
If not then wire to dash board battery light is damaged, this wire is the ON/OFF switch for alternator.

If all wires test as they should then replace alternator

Thanks very much. I'll look at all that when I get home!!! But. Where is the fuse or fuse able link located?
Thanks

How do you know it isn't charging? Battery going down or just ammeter not showing it charging?

Volt meter not showing charge. And battery was to low to start it. Got a jump. So should of been running on alternator. But wouldn't stay running. At lunch I went to auto zone for them to test it. It failed. Oreillys was the 1st place that tested it. They passed it. I'm going back to oreillys for a retest. Cause that's where I got it from. Hoping for a warranty replacement.

Thanks

Well good luck, hopefully they make it right.

Racenut said:

Thanks very much. I'll look at all that when I get home!!! But. Where is the fuse or fuse able link located?
Thanks

Click to expand...

60 amp fuse will be in engine fuse box.
Ford used fuses and fusible links interchangeably over the years

Fusible links will be on the Battery post of the starter relay on inner fender.
Follow Positive battery cable, it will go to starter relay post, on that same post will be several other wires, almost all will be fusible links.
Fusible link is one or two gauges smaller wire than "protected" wire, they are usually 6"-8" long and "may" have a tag saying fusible link.

Point of using a fusible link is that they don't "Blow" on quick amp spikes like fuses do, they heat up but stay connected, these are popular to use with alternators since they can spike amps now and then.
Fusible link will "blow"/separate if heated up enough.

RonD. The green wire has no 12v with key on. So I applied 12v to it. And it started chargeing. I traced the green wire back to the fire wall. But then lose it. Where does it get its power from? The fuse block? If I can not find n fix the green wire. Can I just tap in switched 12v to the green wire and every thing ok?
Thanks

Green wire runs to the Battery light in the dash board.

It won't hurt it to run it that way, but, No, you can't leave it hooked up or battery will go dead when engine is off.
Alternator is basically an electric motor used in reverse, if green wire was left on(12volts) then when engine was off alternator would try to turn fan belt/engine, which of course it can't, but battery would drain as it tried to.

The way the battery light works, it that the alternator is a Ground when it is off.
When you turn on the key one side of the battery light gets battery voltage, the Green wire hooked to the other side of the battery light goes to alternator, which is a Ground now so battery light bulb glows, lights up.
When you start the engine, and alternator is working, then the Green wire now also have 12volts.
With 12volts at both sides of the Light Bulb no power is going thru the light bulb so it is not glowing, it is OFF.
And ff alternator should stop working while engine is running...........battery light comes on.

So it is a pretty simple circuit.

Diagram here: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_2.JPG

You are looking for the LG/R wire, Light Green/Red stripe wire

There is also a resistor with the light bulb, diagram shows it as 510, that is there in case light bulb should burn out, if bulb burned out then no charging like you have now, but with resistor there it would still pass the 12volts to alternator, could be both the bulb and resistor failed but that would be a long shot.

You will have to check under/in dash to see why green wire has no voltage.
If you have a voltage meter in the dash it can run thru there as well

Switched 12v won't hurt a thing.

I just wired one of these up to work in a tractor, this might help you (without the confusing white wire even)



Mark has a good pic on the last page of that thread if you want some more diagrams to fish through.

http://www.therangerstation.com/forums/showthread.php?t=162916&page=3

I'd do more testing/troubleshooting (see diagram below) and try to fix it; but, I don't see why you can't use switched power to the light green wire to make the alternator work.

Only problem I see is you will never know when the alternator stops alternating. I think I would put an inline fuse in there so if something happened you would not burn down the truck.

http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_1.JPG

I couldn't find where the green wire was broken or unplugged. So I used one of those fuse taps that piggy backs an existing fuse. Just plugs in. I'm useing the power lumbar ( not sure what else is on it) circuit. #18 on the fuse chart I think. Now I am charging around 14v depending on load. Haven't driven it yet. Just ran n driveway.

And I don't think my alt dash light is working. It didn't come on when it wasnt charging b4.

As long as the "lumbar fuse" turns off with the key you should be fine for now.
If green wire has power 24/7 the battery will drain fairly fast.

You can add a 12v light bulb on the new wire, that will work the same as the Battery Light in the dash
Key on engine off the bulb should be on, after starting engine. and alternator is working. bulb will go off.