Hey guys, my truck always kept 14.2 V while driving and lights, accessories and motor blower is on, recently it started to go down, meaning if I turn the headlights on it drops to 13.9 and if i add the motor blower it drops to 13.7, I had a new alternator and put it on and it is still doing the same thing, the batteries are 2 months old and they aren’t the cheap kind, it used to go to 14.2 in the morning as soon as I start it, now it is slowly going up, I checked the serpentine belt also good, any idea where to start ? It’s a 379 with C15
Batteries charge
Discussion in 'Ask An Owner Operator' started by Zicko1993, Mar 7, 2025.
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Not likely to be the alternator as you replaced it. I would still have it checked along with the batteries with the newer conductance type testers. Then clean grounds and coat with either dielectric grease or fluid film. See if you can use a voltmeter in place of the gauge. Truck is at least 18 yrs old so bad cables are possible. Voltage drop easy to check with one lead at one end of a cable and other lead at other end. Plenty of online videos.
Check drop on the + side below by placing one end of the meter on the B+ at the alternator and the other on the + at the battery. Retractable leads are $10 - $30 as multimeter leads are not long enough.
![[IMG]](proxy.php?image=https%3A%2F%2Fimages.saymedia-content.com%2F.image%2Ft_share%2FMTc0OTYyMDMwODE2NzMzMDMw%2Fcharging-system-voltage-drop-test.jpg&hash=6394b3c597a4c05f57fb4fd1915e52c4)
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