alternator won't charge
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New User
Joined: Jan 2009
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alternator won't charge
To cOOnhunterjoe and one farmer. Ford F-350 1997 7.3 diesel. Tested the meter with another battery and it checks ok. Did the following test. With truck off and key off tested the battery 12.87 volts. Tested from the - post battery to large post on alternator 12.87 volts. Tested from - post battery to left hand wire 12.87 volts. Tested from - post battery to middle wire .03 volts. Tested from - post battery to right wire 0 volts. Next test was motor off key on. Tested the left wire 12.87, middle wire .02, and right wire 0 volts. The last test I did was motor running. Tested from - post battery to large post alternator 12.76 volts, to left wire 12.76 volts, to middle wire 6.35 volts and to right wire 12.76 volts. I hope this makes some since to you. I'm getting cold riding a dirt bike to work. Again I can't thank you enough for your help. Ford nc.
Post Fiend
Joined: Oct 2003
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From: MICHIGAN
Not sure about your previous posts with Joe & Farmer but if you want to check your alternator put the probes on the - and + posts on one of the batteries. Check with the engine idling and the glow plugs cycled off.
You should see 13+ volts with all electrical components on (radio, lights, heater fan on high, ect.)
You should see 13+ volts with all electrical components on (radio, lights, heater fan on high, ect.)
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Jim I have changed the alternators and when tested on the truck it shows no output. Joe and farmer have been helping me. Those test where done this morning. I changed the alternators back and forth between the new one and the old one. Both test good on the stand but show no output on the truck.
Post Fiend
Joined: Oct 2003
Posts: 5,903
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From: MICHIGAN
Sounds like a bad fuse (fuseable link) or bad wire connections. The fusable links (Grey 12 Gauge) are attached to the starter relay on the fender. Check the wire connector on the top of the alternator for loose or damaged pins on the connector. Those wires get damaged form being laid on when working in the engine compartment.
Here's a diagram and Pinpoint tests:
Here's a diagram and Pinpoint tests:
Lead Driver
Joined: May 2007
Posts: 8,608
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From: Belair md
huh, i just opened your pdf's jim, i am way behind...lol,,,,
i gave him the wires to check a few topics back so this is his results from the test
from the results it sounds like a bad alternator, your voltages with the truck running are correct, my advice is first, make sure the pins on the 3 wire connector are making good contact as jim said, and second take both alternators to the parts store and have them bench tested. your wiring sounds good.
i gave him the wires to check a few topics back so this is his results from the test
from the results it sounds like a bad alternator, your voltages with the truck running are correct, my advice is first, make sure the pins on the 3 wire connector are making good contact as jim said, and second take both alternators to the parts store and have them bench tested. your wiring sounds good.
Senior User
Joined: May 2007
Posts: 112
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From: ST JOHNS, MI
All the voltages are correct to the points that you tested. Sounds like either a bad connection in the three wire connector where it plugs into the alt or a bad alt. If you took the alt in to be tested and it showed good, the connector is suspect.
Also did you find the screw on the back of the alt that says "test here" and did you try grounding it? The engine needs to be running for this test. This full fields the alt in effect bypassing the regulator. If the alt charges with this test then the problem is either in the regulator or that connector not getting power to the regulator.
When you do find the problem be sure to come back and let us know!
Also did you find the screw on the back of the alt that says "test here" and did you try grounding it? The engine needs to be running for this test. This full fields the alt in effect bypassing the regulator. If the alt charges with this test then the problem is either in the regulator or that connector not getting power to the regulator.
When you do find the problem be sure to come back and let us know!
