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Discussion Starter · #1 ·
charging question. My 09 6.7 cummins wouldn't start this morning. Battery terminal was corroded so I cleaned and jumped it. the gauge is showing just over 14 volt charge and a volt meter on the battery is comfirming so. Shortly after it was running the gauge dropped to about 10 volts (meter confirmed this), then within a few seconds went back up to 14.5-15 volts. it kept doing this for a few minutes then stopped. Is this normal? Anyone else experiencing this and how did you fix it? Thanks
 

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If it still does it after all that ^^^^^ then it's time to get the alternator & battery tested. Should be over 12VDC at rest and over 14VDC (high 13 if multiple accessories are running) while charging.
 

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Discussion Starter · #4 ·
So I did have a bad battery. Replaced both but the voltage is still dropping to 10 but goes right back up. Someone told me this could be normal and some kind of cycle it goes through for a few minutes cause it stops. He said he had a 7.3 that did this cause of his glow plugs kicking on. I will take it and have it tested again now that I have new battery.
 

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charging question. My 09 6.7 cummins wouldn't start this morning. Battery terminal was corroded so I cleaned and jumped it. the gauge is showing just over 14 volt charge and a volt meter on the battery is comfirming so. Shortly after it was running the gauge dropped to about 10 volts (meter confirmed this), then within a few seconds went back up to 14.5-15 volts. it kept doing this for a few minutes then stopped. Is this normal? Anyone else experiencing this and how did you fix it? Thanks
How cold is it outside? It sounds like the cycling of the intake air heating screen. It draws a heck of a lot of current and can draw the battery terminal voltage down. BTW the terminal voltage at “normal” temp should be 13.2 volts (2.2V X 6). The terminal voltage will vary with outside temp going up as it gets hotter. Also the voltmeter in the dash is OK, but it’s not that accurate.
Steve
 

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charging question. My 09 6.7 cummins wouldn't start this morning. Battery terminal was corroded so I cleaned and jumped it. the gauge is showing just over 14 volt charge and a volt meter on the battery is comfirming so. Shortly after it was running the gauge dropped to about 10 volts (meter confirmed this), then within a few seconds went back up to 14.5-15 volts. it kept doing this for a few minutes then stopped. Is this normal? Anyone else experiencing this and how did you fix it? Thanks
That is normal. When the truck is first started the heater grid on the intake cycles on and off until the correct temperature is reached.
 

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Discussion Starter · #7 ·
How cold is it outside? It sounds like the cycling of the intake air heating screen. It draws a heck of a lot of current and can draw the battery terminal voltage down. BTW the terminal voltage at “normal” temp should be 13.2 volts (2.2V X 6). The terminal voltage will vary with outside temp going up as it gets hotter. Also the voltmeter in the dash is OK, but it’s not that accurate.
Steve
It was in the 40’s
 
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