lack of charge. this son of a #$%#
#1
02-17-2008, 08:46 PM
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lack of charge. this son of a #$%#
I currently working on an 87 F250 with a 6.9. for some reason it is not charging. I have no great knowledge of electricity but Im stumped. I replaced the alternator with the one off my 91 7.3 wich I know works. I bought a new voltage regulator and no difference. If I get it running and put my volt meter on the alternator It reads .24-.25 at idle or higher rpm. what could this mean? It should be like 13-14 right? like I said the alt is good for sure. any help?
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02-17-2008, 09:41 PM
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02-17-2008, 10:14 PM
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I am assuming that the 91 is the standard alternator without the built in regulator.
The black/orange heavy wire will feed voltage back to the battery through a fuseable link- a green section of wire close to the battery or relay. This wire sould be reading battery voltage, revese current is prevented from running back through the alternator by the diodes(internal in the alternator). The s white/black wire is normally a tap off the windings (stator) that works the idiot light, and provides a sense voltage to the regulator, and the f feild wire is the exciting voltage from the regulator. With the truck not running you may see those low voltages on the feild wire, but runnning the voltage will build up to 12-14V depending on the load applied to the alternator.
Check that the fuseable link is not burned out., then for loose or broken wiring on the regulator plug or alternator connections. A bad alternator will toast a new regulator, so if you changed out the regulator before you did the alternator, that could be the problem as well. Also just because a regulator is new doesn't mean it was any good out of the box! With the Feild wire disconnected,and belt loose or off, with an ohm meter you can check the brushes, commutator, buy measuring the resistance to ground, on a 12 V system should be 6-8 ohm+/-, a dead short in the feild will give you 0 ohms, worn or dirty brushes and commutor will give you much higher resistance, or will jump all over the place as you rotate the rotor. Infinite resistance means the feild circut is open, no output from the alternator. Hope this helps you isolate the problem.
The black/orange heavy wire will feed voltage back to the battery through a fuseable link- a green section of wire close to the battery or relay. This wire sould be reading battery voltage, revese current is prevented from running back through the alternator by the diodes(internal in the alternator). The s white/black wire is normally a tap off the windings (stator) that works the idiot light, and provides a sense voltage to the regulator, and the f feild wire is the exciting voltage from the regulator. With the truck not running you may see those low voltages on the feild wire, but runnning the voltage will build up to 12-14V depending on the load applied to the alternator.
Check that the fuseable link is not burned out., then for loose or broken wiring on the regulator plug or alternator connections. A bad alternator will toast a new regulator, so if you changed out the regulator before you did the alternator, that could be the problem as well. Also just because a regulator is new doesn't mean it was any good out of the box! With the Feild wire disconnected,and belt loose or off, with an ohm meter you can check the brushes, commutator, buy measuring the resistance to ground, on a 12 V system should be 6-8 ohm+/-, a dead short in the feild will give you 0 ohms, worn or dirty brushes and commutor will give you much higher resistance, or will jump all over the place as you rotate the rotor. Infinite resistance means the feild circut is open, no output from the alternator. Hope this helps you isolate the problem.