Alternator Voltage
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Mountain Pass
Joined: Apr 2013
Posts: 101
Likes: 4
Alternator Voltage
I have a 2014 F150 5.0 with an intermittent alternator issue. It started with the battery going bad and since then I get an occasional battery warning symbol on the dash. I’ve replaced the battery and the charging system tested ok. I have a phone charger plugged into the cigarette lighter that shows voltage. It mostly reads 14.4 but a couple times it has read 13.3 or so for 30 minutes during my trips to work. Since I replaced the battery the battery alert has only come on two or three times in 2 1/2 weeks. The one time I had the phone charger showing the voltage it read 14.4 when I looked over at it. I don’t know if the voltage is good even when the alert is turning on or if it is a momentary drop in voltage that I haven’t been quick enough to see or test. My understanding is that below 13.5 volts is out of spec for my truck. I’m guessing the regulator is going bad but since I haven’t been able to test the voltage when it’s low enough to trigger the warning I hesitate to spend the money on a new alternator. What does this sound l8ke to you?
Tuned
Joined: Dec 2012
Posts: 409
Likes: 106
Turn on all accessories in the truck and see how much the voltage drops (lights, fan , defroster, etc). 13.3 isn't terrible but if it goes into the 12s under high load the alternator may be tired.
Also wiring to the alternator could cause issues too.
Also wiring to the alternator could cause issues too.
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Mountain Pass
Joined: Apr 2013
Posts: 101
Likes: 4
I have wiggled the wires but saw no change in voltage and the alert didn’t light up. The voltage only goes down 0.1 volts when everything is turned on.
Tuned
Joined: Dec 2012
Posts: 409
Likes: 106
Clear out any trouble codes, and wait till it happens again, if you see any low voltage codes there may be a tiny interval where it dips and your volt gauge can't pick it up (probably needs a second to respond).
I don't think your alternator is bad, that is not to say there can't be a loose component in the electronics.
Hotshot
Joined: Jul 2005
Posts: 11,931
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there is a PLUG near the negative cable on the battery that MONITORS battery charge and tells the alternator regulator what to do.. I would UNPLUG that small unit and then see how things work..
Google BMS ... battery management system...
Google BMS ... battery management system...
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Hotshot
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Mountain Pass
Joined: Apr 2013
Posts: 101
Likes: 4
My 2014 has the old style BMS with the current sensor around the negative cable. I had never heard of it and had no idea I had to take special steps when changing or replacing the battery. It very well could be the problem. I recharged the battery when this began and didn’t connect the charger to a body ground instead of the negative terminal. Now I know. I’m currently going through the BMS reset procedure even though it’s been a couple weeks since I put the new battery in. Thanks for the help, I had no idea to even look for this.
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