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Troubleshooting a charging system

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Old 12-03-2003, 09:17 PM
salewit salewit is offline
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Troubleshooting a charging system

Hi. I have an 84 F250 1ton Diesel (dual batteries).

What would be the procedure on checking a charging system? I'm not 100% sure the system is charging properly. I ran the batteries down the other day on a cold morning, and had the same situation a couple more times. The batteries I know to be good (both 6 months old, both took a charge).

When I volt test the fully charged batteries with the engine OFF, I get about 13.8 volts. After using the vehicle at night for about 30 minutes, then checking the next day with the engine running, I get about 11.7 volts at the batteries. Shouldn't the alternator be kicking the voltage up to about 14+ volts?

I've been putting the truck on the trickle charger every night for the past week for fear of getting stranded somewhere.

What is the next step short of removing the alternator and regulator? Do I test the voltage between the field connector and ground on the alternator?

I know this question has been asked before, but the system wouldn't allow me to do a search (server busy message).

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Old 12-04-2003, 03:01 AM
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Mike W Mike W is offline
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Yeah, you should be getting around 14 volts at a fast idle. Check the voltage at the field terminal to ground. If you have about 11 volts, the alternator is bad. If you have 0 volts, the regulator or wiring is bad.
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