Hey guys i had a question for you. I have been getting low voltages on my batteries, granted its been really really cold here, like -4 at night, and i have seen my voltages drop to 9.8 volts, now i just replaced these batteries, they are die hards, 880 CCA, i took the alternator out and it tested fine, and i just replaced my ficm too. Now when the truck is warmed up the battery voltage is 12.8 to 13.4 volts. I am starting to wonder if my alternator is acting up even though it tested fine. Do these voltages seem normal or am i right in thinking they are too low for new batteries and a "good" alternator? Also i do plug my truck in at night, so that helps...
mikeb01453
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1,009 Posts
A battery needs 13.8 volts to initiate a good charging cycle. Average running voltage on my 6.0L was 14.2 volts. I'd suggest looking into another alternator or running a monitor to watch live output numbers (voltage meter) that are being run through the system. 9.8 volts is far too low, and cold starting a diesel with low voltage is hard on an engine and computer components.
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Repeated cranking with voltage starting/hanging in the 9's will fry your FICM as it tries to amplify voltage.
I ran top of the line batteries and never saw below 11.2V cranking. Of course plugging the truck in is what's allowing you to start the truck at all.
It's normal to see a dip into the low 10's high 9's in a normal situation after the glowplugs have cycled and the engine has cranked. What's not normal is to see an alternator not putting out enough voltage to initiate a deep charge cycle on a battery. Eventually the batteries will fail-they just aren't set up to handle this repeated situation.
I ran top of the line batteries and never saw below 11.2V cranking. Of course plugging the truck in is what's allowing you to start the truck at all.
It's normal to see a dip into the low 10's high 9's in a normal situation after the glowplugs have cycled and the engine has cranked. What's not normal is to see an alternator not putting out enough voltage to initiate a deep charge cycle on a battery. Eventually the batteries will fail-they just aren't set up to handle this repeated situation.
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