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I've noticed during cooler weather that my voltage seems to be low on the truck. The first two pictures are in the 30s to 40s outside and the third was this morning in the low 50s. According to the auto parts store, the alternator and battery read fine for their test and I don't leave anything plugged into the trucks outlets. Should I be concerned about the gauge or is this normal?
The truck is 18 years old. How old is the alternator ? How old is the battery ? You need to put a voltmeter on the battery while setting, then while running to see if you are getting a good charge......... In general, an alternator will last 150- 175K miles... Some longer, but your pushing it.
The battery gauge is fake, it's most likely a failed and sticking stepper motor in the gauge. Enter test mode on the cluster and you can sweep all the gauges. Use a voltmeter to verify alternator, low voltage is only indicated by the actual battery light in these trucks.
Truck only has 25k miles and I don't know how old the battery is but both AutoZone and O'Reilly's stated the alternator and battery passed their test with O'Reilly saying the battery needed a charge. Both said that the battery appeared to be new and is a duralast battery.
I know the odometer goes on and off when I'm driving and have found a thread on how to fix that. I was contemplating swapping it out for one with a tach but seems to be a little involved to get that work.
YOU have to test monitor the system voltage either at the battery terminals or at the 12 volt port in the Cab.
At very least get an LED stick monitor from one of the auto stores. Very inexpensive.
Plug it in or wire it to see the system performance full time.
Don't depend on a store test when you can see all you need right on the vehicle.
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The dash gauge does not directly monitor the system voltage. Notice there are no voltage points or other markings on it's meter face that tells you anything.,
The so called gauge is driven from a Chip to a fixed reading level and that is it.
Many of the other gauges are handled the same.
For more example, the Oil gauge tells you nearly nothing about the oil pressure. I reality, that gage is driven by a "SWITCH", not varying pressure, that closes at about 8 psi. Bet you would be alarmed if you saw that on a dash gauge!.
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If you see the charge system is working normal, the dash system has a fault. You have to make a decision if you want to fix the dash read-out.
Good luck.
Thing about monitoring battery or charging voltage, for any sort of serious diagnostic or troubleshooting work it has to be measured directly at the battery posts, because that's the only thing that counts. A tenth or two of a single volt one way or another doesn't sound like much, but it looms large when talking about percentages and state of charge.
Those dash plug-in voltage monitors are handy, but typically indicate about 0.5 volts low from actual voltage at that location. That's a lot. Keep in mind the difference between 100% full charge and "Dead Right There" is less than a single volt. Somewhere between 13.8 and 14.2 volts is normal charging voltage. More in cold temperatures, less as temperature increases.
Ford went to counterfeit or dummy gauges a long time ago apparently.
Sounds like I've got a couple more things on my to do list this weekend when I get my PCV valve and associated hoses along with fuel filter and oil pressure switch. Fortunately I have a battery powered jumper in case the battery does go between now and then.
So battery tested fine and it's the guage itself failing. Guy I work with used to own this body style but in a crew cab told me of a feature where you hold down the trip button to bring a series of test on the gauges. The voltage was the only one that didn't move. I did fix the odometer blackout issue as well as the pcv valve today so hopefully that will be it for a bit.
