Battery not charging
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Mountain Pass
Joined: Dec 2003
Posts: 168
Likes: 0
From: NJ
Battery not charging
I replaced my alt. because in the morning the bearing would squeak and the head lights flicker. It was a life time alt. warrantee from Adavanced. Put the new one in now it wont charge. Took it back and got another, same thing. Also replaced the starter relay and battery. I checked the fusible links and replaced a terminal connector. The wires look good. There is 12v on the alt lug and pins 1 and 3 on the connector with the key off. Turn key on and 12v disappears form pins 1 & 3. Also checked all fuses in both boxes. I ohmed out the wire harness from the alt back to the connectors, all good. What am I missing? This is a 99 f530 5.4l.
Postmaster
Joined: Sep 2010
Posts: 3,472
Likes: 2
From: Southern Cal
There's 12v on the alt lug be causes it connects directly to the battery. What voltage do you see with a vom when the engines running at that lug?
You should expect to see between 13.8-14.4volts running.
Also check at the battery knowing you'll have a slightly lower voltage due to wire resistance.
The battery should show about 12.6-12.8v if good and charged.
The other two wires simply notify your dash is not charging properly and "excite" the alternator at start up, unlike a 1- wire alt.
You should expect to see between 13.8-14.4volts running.
Also check at the battery knowing you'll have a slightly lower voltage due to wire resistance.
The battery should show about 12.6-12.8v if good and charged.
The other two wires simply notify your dash is not charging properly and "excite" the alternator at start up, unlike a 1- wire alt.
Token Redneck
Joined: Jun 2007
Posts: 9,335
Likes: 344
From: Breckenridge, TX
This is really really dumb but it's a true story... I had a pin back out of the wiring connector at the alt when I changed mine, and the way the wiring loom was taped I couldn't tell just by looking at it when it was plugged in, I had to remove the connector and look inside it. Make sure a pin didn't back out of the connector.
Lead Driver
Joined: May 2003
Posts: 9,303
Likes: 48
From: Lyndonville, Vermont
Battery 12.7 after flash off...lights on for 1 min..
Charging voltage 14.4 volts engine running.
Light on dash is needed for operation so that is good. Unplug alt.. light should go out. The regulator turns it off if alt is charging. Check single connector they go bad. Get alt checked on bench.
Charging voltage 14.4 volts engine running.
Light on dash is needed for operation so that is good. Unplug alt.. light should go out. The regulator turns it off if alt is charging. Check single connector they go bad. Get alt checked on bench.
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Mountain Pass
Joined: Dec 2003
Posts: 168
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From: NJ
Unplugged connector and no bat light on dash. I checked the single connector and there is continuity. Can I disconnect the bat cable to alt and check the voltage at the lug? Does the alt output without the cable connected?
Lead Driver
Joined: May 2003
Posts: 9,303
Likes: 48
From: Lyndonville, Vermont
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Lead Driver
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Postmaster
Joined: Sep 2010
Posts: 3,472
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From: Southern Cal
Expect the batteries to show 12.8v fully charged, 12.6 at 75% charged.
Carefully put a long screwdriver on the alternator pulley while running. You should feel a magnetic pull if operating.
While operating, expect to see approx 14.2-4v at lug. Not close!
New alternator next.
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