Voltage Bleed off / Loss
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Voltage Bleed off / Loss
My battery indicator has recently started showing a drop in voltage. when the head lights only are on, it seems to be fine. If I turn on my heater/defrost and bump it to max, then the voltage drops from approx 14.5 down to about 11. if i back the heater down one, then it will bump up about 1 volt. If I am slowing down, then the voltage looks to bleed off from 14 down to and if I apply the breaks, while at a stop light then the voltage bleeds down to about 10 or 11 volts. the lights go dim the heater slows down etc. I have replaced the Alternator with one that passed bench test prior to my replacing it still not good. . I tried cleaning the battery term. no good. I tried a different battery. No good. I am needing some input.
Barry
Barry
Senior User
Joined: May 2004
Posts: 194
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From: Waterford Michigan
that is exactly what I would check. make sure the tensioner is showing correct tension on your belt. it could be that the belt has just worn out is streched to far to maintin proper grip on the pullies.
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Or, a poor connection at the starter relay on the fender well for the fuse link that feeds the distribution boxes, or a poor connection at one of the boxes. The gauge is driven by local connections. It could as well be a poor ground in the cab.
Likewise, it could be the bearings in your fan motor are getting a little stiff, causing extra load on the fan motor circuit. The latter seems to be the culprit more often than not. Yank the blower out and see how freely it turns. If there's any stiffness in the bearings at all, the next thing that will happen is that the burden resistors for the various speeds will burn out and you'll only have MAX speed. I've never had to pull mine out, but most of the time, the little motors can be separated (a lot easier than they can be put back together) and some fresh lithium grease put in the bearings. Usually does wonders to delay the impending doom of the motor.
Likewise, it could be the bearings in your fan motor are getting a little stiff, causing extra load on the fan motor circuit. The latter seems to be the culprit more often than not. Yank the blower out and see how freely it turns. If there's any stiffness in the bearings at all, the next thing that will happen is that the burden resistors for the various speeds will burn out and you'll only have MAX speed. I've never had to pull mine out, but most of the time, the little motors can be separated (a lot easier than they can be put back together) and some fresh lithium grease put in the bearings. Usually does wonders to delay the impending doom of the motor.
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Instead of useing the volt meter in the instrument panel, use a real meter like a mulitester at the battery. $5 at Harbor Freight and you can use it for a bunch of different tasks in the house and for automotive. Measure across the battery terminal with the engine off you should see about 12.5 volts. Start it up and let it idle, and you should see almost 14 volts. Start turning on different electrical items and see what the voltage does. If it just drops a hair at the battery, that is normal. Full electrical load on mine give me about 13.5 volts at the battery. If your instrument cluster gauge is dropping more than actual, you probably have a bad ground for the instruments, or bad connection in the wires coming off the solinoid. The good thing is, work on it if you want, but you can stop worrying about it if the voltage stays up at the battery. As long as the battery voltage stays up, the alternator, and voltage regulator are doing their job.
Good luck Frank
Good luck Frank
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Joined: May 2007
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From: Solon, Ohio
Measuring across a good battery with everything off and using an accurate meter should give you a reading of 12.70 - 12.80 volts.
With engine running and everything else off, you should read about 13.4 volts.
If ideling while in gear, (automatic), it is normal for the dash meter to drop and the lights to dim if your heater is on. At a low idle your alternator just doesn't turn fast enough to supply enough current to fully power your lights and heater. That's one of the reasons you have a battery,.........to give you a reserve when you need it.
With engine running and everything else off, you should read about 13.4 volts.
If ideling while in gear, (automatic), it is normal for the dash meter to drop and the lights to dim if your heater is on. At a low idle your alternator just doesn't turn fast enough to supply enough current to fully power your lights and heater. That's one of the reasons you have a battery,.........to give you a reserve when you need it.
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if his is like mine was, it drops to the point where it's about to die. lights become very dim and the fan slows WAY down.
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It does drop to where it runs very rough. I did replace alternator with one that passed Bench test before installing. no change. I changed Serpentine Belt. No change. I changed belt tensioner. No change. I have fiddled around with wires to check for loose connections, no luck. I am lost.
My friend also says check for bad grounding and fusible links. I will check that next.
My friend also says check for bad grounding and fusible links. I will check that next.
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Elder User
Joined: May 2007
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From: Solon, Ohio
Like I stated above.................It's NORMAL for these trucks.
The only way your going to change it much is to go to a bigger, newer tighter battery which will make it less noticeable, or switch to a smaller alternator pully.
Unless your truck just plain idlles too slow.
The only way your going to change it much is to go to a bigger, newer tighter battery which will make it less noticeable, or switch to a smaller alternator pully.
Unless your truck just plain idlles too slow.
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