Weird Voltmeter Reading

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Oct 30, 2012 | 10:57 AM

JDFan4010

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Weird Voltmeter Reading

When I get in to start the truck (1990 F250 7.3 n/a) my voltmeter shows 10 volts, after wait to start light goes out, it reads 11 volts. Readings of 1 year old batteries in 12.56 & 12.52 with cables off. After running it it gets up to about 14 volts. It seems fine to start, but I would think it would read 12.5 volts after glow plugs have heated. Do I need to concern myself with this? If so what should I do next?

Thanks,

JDFan4010

Oct 30, 2012 | 11:06 AM

hairyboxnoogle

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Sounds about right to me, after letting it sit, what do the batteries read with cables on before turning the key on?

GPs pull one hell of a load, so the batteries will read low for a sec i would guess. If it starts fine, i wouldnt worry about it.

Oct 30, 2012 | 02:13 PM

JDFan4010

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OK, I wont mess with it then. Thanks.

Oct 30, 2012 | 02:15 PM

SnuffthePunkz

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From: Surrey, BC, Canada

They aren't in a bad zone yet, but it sounds like they are just starting to get tired. Likely in a year or two you may have issues though.

Oct 30, 2012 | 02:38 PM

JDFan4010

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Quote:

Originally Posted by SnuffthePunkz

They aren't in a bad zone yet, but it sounds like they are just starting to get tired. Likely in a year or two you may have issues though.

Snuff- your talking about the batteries right?

Oct 30, 2012 | 02:42 PM

SnuffthePunkz

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From: Surrey, BC, Canada

Yeah as hairy said you have nothing to worry about right now. Just keep it in the back of your mind when a couple years down the road comes along and things start acting up to get them tested at a battery shop before you start ripping everything else apart.

Oct 31, 2012 | 06:48 AM

hookedondiesel

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From: Rockland Ontario

Quote:

Originally Posted by JDFan4010

When I get in to start the truck (1990 F250 7.3 n/a) my voltmeter shows 10 volts, after wait to start light goes out, it reads 11 volts. Readings of 1 year old batteries in 12.56 & 12.52 with cables off. After running it it gets up to about 14 volts. It seems fine to start, but I would think it would read 12.5 volts after glow plugs have heated. Do I need to concern myself with this? If so what should I do next?

Thanks,

JDFan4010

Just curious, when you say "after running" did you mean, with the cables disconnected you were getting 14 volt's, or was that while it was running.
A battery that shows 14 volts "on it's own", will not last long, it's cell's are shorting.