F8000 Ford won't stay charging

[Jons]

Hello I have a 1993 Ford 8000 with a 8.3 Diesel and it will not keep charging the batteries. Have two new batteries, new alternator. Will charge for about one minute 14.1 volt then stops charging, if you turn ignition key off and then back on again it will charge for a another minute or so. Did the same thing with the old batteries and old alternator. Any ideas. Thanks in advance Jon

 

[grandpa]

Behind the air cleaner is a voltage regulator.... unplug it and jump the two wires on each end of the plug in.... if it stay's charging its your voltage regulator.

 

[Jons]

Wow that was fast will try first thing tomorrow. Thanks Grandpa

 

[grandpa]

No problem Jons.... let us know what you find.... and welcome to the forum.

 

[Jons]

Just dawned on me truck is a L8000 not a F. Jon

 

[grandpa]

No problem.... the advice was for an L

 

[Jons]

Ok looked at truck no regulator behind air cleaner. What about ignition key switch. ??

 

[Steve Frazier]

I'd continue to look for the regulator, that's your most likely suspect. Just to clarify, are you reading your power output with an independent meter or from the dash gauge?

 

[overworked]

93 should have internal regulator in alt. Check voltage at batteries or alt, volt meter in dash runs through cab harnes and relay

 

[grandpa]

I don't think it would be the ignition switch because it starts charging... switch wouldn't make it stop in most instance's.

 

[Jons]

Reading output both at gauge and at batteries, when gauge drops back after one minute voltage at batteries goes from 14.2 to 12.97 so gauge is showing the drop, also if lights are on you can see the drop in voltage. Cant find a regulator on firewall. Where would the relay be located. Picked up new ignition switch thought would try tomorrow.

 

[stumpjumper83]

are you using a remanufactured alternator by chance? A lot of times they just do a point of failure repair and a paint coat...

 

[overworked]

12.97 is still charging, at idle with lights on might be normal. My L8000 shows every light you turn on drops volts on gauge, what about at 2000 rpm?. Relay is under dash on mine 1988.

 

[Jons]

No when quits charging it quits, only 60 to 90 seconds after starting makes no difference of rpm at 2,700 still no charge. If you flip key off and back on starts charging for 60 to 90 seconds, I have fuel shut off disconnected so motor does not shut off when you cycle ignition switch. Has done this same thing with two alternators the original one and the reman. It will run batteries down if you have lights and heater on after one hour or so. This relay what would it look like. Will look again tomorrow will hold off on ignition switch which I can return.

 

[Old Doug]

Did you have old alt checked? What about checking to see if wires on alternater are hot. One big one is hot all the time and there should be a wire that is energised by the switch. I would check them with it charging and after it quits.

 

[Jons]

Old alternator used to do same thing and finally failed so had it rebuilt. Wondering if should take back and have shop check output for a couple of minutes to see if it has a internal regulator, and that is acting up. ??

 

[grandpa]

Would be as good as place as any to start. That relay you would be looking for is above and to the left of the heater control box. Its usually a little chrome looking thingy...lol... kinda hard to get to, but it can be done...

 

[Jons]

Ok put alternator on bench stays charging fine. Something that I have overlooked is this truck has a alarm system that shuts down if high temp, low oil pressure, low coolant level. I now think the 60 to 90 seconds has something to do with that, If I hook the fuel shutoff up that shuts down the engine at the 60 to 90 seconds also. Any one know anything about the alarm system. Think its a Kyser ?

 

[grandpa]

I don't think that's the problem.... did you ask if this alternator has a built in regulator?

 

[Jons]

Built in regulator none on firewall, alternator puts out 14.0 plus volts on test stand for as long as you run it. Forgot about the Kysor engine shut down and alarm system that's why I disconnected the fuel shut off it would shut off engine every 60 to 90 seconds, but with it disconnected can still run truck but lose voltage.