Ford charging system problem

wheelingexp

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Joined
Jul 15, 2010
Location
South Mountains
Got a 89 motorhome with ford drive train with a 460 non-efi.Ran great for years.The alternator came apart in side.So I had it rebuilt and replaced the voltage reg.Still wont charge.Check all the wires .Can't find the problem.Would rewire but don't know extactly where they all go.Wondering if the ingition module could have any thing to do with it? Any help would be great
 
id look into getting a new alternator. if you're reusing the old one something could've happen to make it inop.
 
It has the big wire to charge the battery and a two wire connecter from the voltage regulator.The regulator has 3 wires.One goes to the alt. one goes to switch and the other I'am not sure.It was rebuilt by a local shop that I've used for years for many rebuilds on varies heavy equipment.So I am sure it was done right.If anybody knows how to or knows someone that can fix it I sure would like to know.Thanks
 
wheelingexp said:
Got a 89 motorhome with ford drive train with a 460 non-efi.Ran great for years.The alternator came apart in side.So I had it rebuilt and replaced the voltage reg.Still wont charge.Check all the wires .Can't find the problem.Would rewire but don't know extactly where they all go.Wondering if the ingition module could have any thing to do with it? Any help would be great
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1- My first thought is the fusible link between the battery and the alternator output. When the alternator fragged it very well could have shorted the output and blew that link, which is essentially just a big fuse. With the vehicle switched off check for +12V at the alternators charging lug to see if it has a good connection to the battery.

2- Just becasue the regulator is new doesn't mean that it's good. I've seen them bad fresh out of the box. It's unusual, but it happens.

3- No, the ignition module probably has nothing to do with it.

4- If you don't know exactly where the wires go, then how do you know it's wired properly now?
 
My guess is either a bad regulator or the regulator isn't getting the control voltage from the dash. The cheap parts-house regulators are crap.

You've basically got four wires to worry about -- ignition, 12V from the battery, field, and stator. Field and stator just run between the regulator and the alt. The 12V from the battery runs to the alt, then a small wire goes to the "A" port on the regulator. Then the "I" port on the regulator goes back to the dash and runs the alternator light. If it can't see 12V on that leg, it won't start charging.

Put 12V to the field wire on the alternator (w/the engine running) and see if it starts making juice.
 
The A wire should go back to the dash and through the "ALT" lightbulb (or ammeter, if we're talking really old-school). It's got two jobs -- the regulator needs to see 12V on that leg, b/c that's how it knows when to start charging. But if the alt starts not making enough juice, there will be a potential difference between the regulator and the dash, and the warning light will glow telling you the alt isn't working.

And now that I type that out... I suspect that a burned-out "ALT" bulb could cause the alt not to charge... but I think you're more likely to have a bad regulator.
 
The a terminal should be battery hot and it gets power from the solenoid/ fuseible link previously discussed. The I terminal is ign hot through the alt light in the dash. There is a 510 ign resistor in parallel with the alt bulb fwiw that will allow the system to still charge even if the bulb blows
 
I just reread the post with an ammeter in the dash instead of an alt light you will have the a terminal to battery hot. F terminal to field and the s terminal on the regulator to ign hot
 
Ok heres what I got.There is no wire at all to the I port.Nothing in the connector at all.The F port runs to the alt.to fire it.That leaves the A and S port.If I put 12 volts to the A port,the alt. starts charging,12 volts.The battery may charge but if you remove the battery cable the engine dies like the alt.s not fireing the ign.The S port wire connects to the wiring harness in the dash and has 12 volts on it but does not make it charge.Also the A wire connects into the ign. wiring.Without running 12 volts to the A wire there is no voltage on it.Checked all the wires.No Bad spots.Like I said been this and working for years.What went wrong?P.S. HELP
 
The A wire powers up from a fusible link near the starter solenoid. It may look ok but the wire can melt inside the insulation. The A wire should be battery hot. The S wire should only have power when the ignition is on.

PS: Pulling the battery cable with the engine running on any vehicle with an alternator is a no-no. That test worked back in the day of generators but without the battery hooked up with an alternator the alternator can spike over 17 volts (Ive seen them as high as 30 volts). That will fry ignition modules and radios as well as pop light bulbs on older stuff and burn up computers on new stuff. A properly working alternator will have .5 to 1.5 volts over engine off voltage. For example: 12.5 volts key off and 13.0 to 14.5 with the engine running.
 
Thanks I'll check to see if the link is fried.Its only got 12 volts or a little under like 11.53 when its charging.i have looked at all the wires and had someone put another set of eyes on it and we can't find a bad wire.So,going do that check and try to get oem reg.Thanks again
 
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