No Charge!
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Joined: Apr 2010
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From: Western Colorado
No Charge!
My '87 F250 isn't keeping it's battery charged. I've only owned it a short time. It didn't have a battery in it when I purchased it. I bought a new battery for it. It fired right up. I noticed a "new" looking alternator in it. As soon as it was running I noted that the volt gauge wasn't moving with the RPMs. Over the next miles I saw that the volt gauge was slowly dropping. Alternator! I visited my Checkers and got a rebuilt alternator. Came home and installed it. Fired up the truck. The volt gauge was in the exact same place it was with the other alternator. Not moving with RPMs. Not charging the now depleted battery. I pulled the alternator and went back to Checkers for a bench test. It passed. I know that a "pass" is no guarantee, but I'm stuck. How do I check the unit while it's on the truck to be assured that the alternator is or is not working properly? A step by step tutorial would be VERY MUCH appreciated! Thanks, Kelly.
P.S. It's an '87 F250 4WD 351. 65 amp alternator?
P.S. It's an '87 F250 4WD 351. 65 amp alternator?
Fleet Owner
Joined: Aug 2005
Posts: 23,666
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From: Easton,Ks
My guess is you have an open fuse link between the battery (starter solenoid) and the alternator.
With the battery disconnected check for a complete circuit from the battery pos (+) cable to the battery plug on the alternator. It is the black wires with an orange stripe.
Also with the battery disconnected check for a complete circuit from the battery pos (+) cable to the "A" plug on the alternator. This would be an yellow wire with a white stripe.
Do these checks with an ohm meter.
If the this all checks good then put 12V dc on the Light Green wire with a red stripe and a volt meter on the battery and start the engine. If it is charging now you have a problem from the Ignition switch to the Light Green wire with a red stripe.
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With the battery disconnected check for a complete circuit from the battery pos (+) cable to the battery plug on the alternator. It is the black wires with an orange stripe.
Also with the battery disconnected check for a complete circuit from the battery pos (+) cable to the "A" plug on the alternator. This would be an yellow wire with a white stripe.
Do these checks with an ohm meter.
If the this all checks good then put 12V dc on the Light Green wire with a red stripe and a volt meter on the battery and start the engine. If it is charging now you have a problem from the Ignition switch to the Light Green wire with a red stripe.
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Joined: Apr 2010
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From: Western Colorado
Thank You for your prompt response. I'll give those a try in the next few days. A few other things have caught my eye. There is a green and white or green and gray wire exiting the loom just behind the alternator. It has a boot on it shaped like a spark plug boot. Any idea what it is or was for? There is also a 2"X2" metal box just to the rear of the starter relay. It has a yellow wire going to one terminal and another yellow wire to the other terminal. Same question, what is it? Thanks, Kelly
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Joined: Apr 2010
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From: Western Colorado
Thanks for your help Subford. While checking for continuity between the battery and the alternator we noticed that the black wire with the the orange stripe was connected to the wrong lug on the starter relay. We switched the wire to the other lug and it is now charging the battery properly. Thanks again, Kelly.
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