Batteries or Alternator? - PowerStrokeNation : Ford Powerstroke Diesel Forum
 
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post #1 of 8 (permalink) Old 03-20-2011, 02:48 AM Thread Starter
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Batteries or Alternator?

Ok so when I get into my truck after work or in the mornings for work my dash voltage gauge is really low about to the red line, the battery light is on as well. I crank the truck up and due to the low voltage it has a slow crank but it does start.

Now going down the road the gauge will go up to a little past the center of Normal. After more driving it will then go back to the center of normal on the gauge and stay there the whole trip. The battery light also turns off after the truck is running.

So I need some input on what would cause the voltage to drop so low after the truck sits for a couple of hours. My only thoughts so far is one of my batteries has a bad cell and is drawing down the other battery.

Any input will be greatly appreciated.

1996 7.3L Powerstroke
T6 Chip with Tony Wildman Tunes
Autometer Cobalt Gauges
3 inch DP, 5 inch Straight Pipe
S&B Intake
Billet Torque Converter, Triple Kevlar Clutches, Transgo Shift Kit.
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post #2 of 8 (permalink) Old 03-20-2011, 05:06 AM
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Re: Batteries or Alternator?

Could also be a parasitic load. Try disconnecting BOTH negative cables next time you park it at home, then hook 'em back up after it's been parked a while. If that helps, then that suggests a parasitic load on the batteries while the engine's off. If the voltage still drops, that suggests one or the other batteries unable to keep a charge. Oh, during this experiment, measure the voltage of each battery right after disconnecting them, and just before connecting them the next time you drive it. You want to check the voltage with the batteries separated from each other like this. This will tell you if one battery is bad.

'Course, it's a bit academic, in that you should replace both batteries at the same time. But it would help to explain what's going on, and of course, you may want to exercise the option of keeping the remaining good battery as a spare.
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post #3 of 8 (permalink) Old 03-20-2011, 05:11 AM
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Re: Batteries or Alternator?

If you have one or can get your hands on one, locate a DC amp clamp meter and connect it to the positive battery cable on the passenger side between the pass side battery and the starter solenoid and see how many amps are being drawn with nothing on in the truck and the doors closed and underhood light off. If it is less than an amp you don't have parasitic drain. How old are your current batteries?

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post #4 of 8 (permalink) Old 03-20-2011, 09:11 PM Thread Starter
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Re: Batteries or Alternator?

Alright I'll have to check the amp draw tomorrow. Also I do not know how old the batteries are, I've had the truck almost a year and these batteries came with the rig.

1996 7.3L Powerstroke
T6 Chip with Tony Wildman Tunes
Autometer Cobalt Gauges
3 inch DP, 5 inch Straight Pipe
S&B Intake
Billet Torque Converter, Triple Kevlar Clutches, Transgo Shift Kit.
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post #5 of 8 (permalink) Old 03-21-2011, 06:05 AM
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Re: Batteries or Alternator?

I changed the batteries about 2 months before you bought it
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post #6 of 8 (permalink) Old 03-21-2011, 11:27 AM Thread Starter
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Re: Batteries or Alternator?

Quote:
Originally Posted by sambosque90 View Post
I changed the batteries about 2 months before you bought it
Alright, I'll have to throw a meter on them to see what's going on. Maybe the extreme cold we've been having has toasted them.

1996 7.3L Powerstroke
T6 Chip with Tony Wildman Tunes
Autometer Cobalt Gauges
3 inch DP, 5 inch Straight Pipe
S&B Intake
Billet Torque Converter, Triple Kevlar Clutches, Transgo Shift Kit.
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post #7 of 8 (permalink) Old 03-21-2011, 11:30 AM
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Re: Batteries or Alternator?

Similar thing happened to me, turned out to be the voltage regulator on the alternator. Cheap fix luckily.

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i have a couple friends that went balls deep in wyotech and when they got out they couldn't poor piss out of a boot if you put the directions on the sole
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post #8 of 8 (permalink) Old 03-21-2011, 02:46 PM
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Re: Batteries or Alternator?

A short in the alt can drain them as well. They will work normally and put out good juice while running, then drain 'em dry while sitting. My big truck did this many moons ago. Had to pull the ground after every day or it wouldn't start in the AM. Ever try to quickly start a big CAT with 4 dead batteries?


Its one of these three things probably...alt, batt or volt reg. I'd rule those out before looking anywhere else. It is a Ford after all.
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