Ok, people have suggested checking my battery because I have thread about my ABS lights and other warning lights or possible phantom lights.
Question:
Is the voltage gauge in the 3 gauge cluster a dummy or placebo gauge?
Does it have any truth to it at all?

Reading the car voltage?

When it does read the car voltage is it reading only from the alternator output when running or battery output when on but not running and what about both at the same time when car running.

I have noticed some deviance in the voltage gauge usually straight up at 14 volts, but have seen it to the left at 12.5 or so but then it goes up. This suggests that it is not placebo or dummy gauge.
The battery is fairly new 6 months or less, but I know Arizona takes them fast.
Again thanks for you thoughts and happy Motoring.

my other thread about ABS warning light.

https://www.jaguarforums.com/forum/x...-itself-73469/

 

It is good enough to tell if your alternator is running or not, or if your battery is very low, but I would not trust it beyond that. Use an inexpensive digital mutimeter at your battery terminals to check it's voltage. Batteries also should be tested with a load tester, which is ususally a free service where they sell batteries.

 

Jaguar decided many years ago that their owners had no reason to be bothered with the fine details of automobile operation. If there was a concern the owner could simply visit their local main dealer who would appropriately deal with the issue.

 

Think of the gauges as three position idiot lights.

 

The voltage gauge is far from a precision instrument but it does seem to act in a pretty linear way, and it is possible to tease some information from it.

Probably the most telling reading is how low the gauge reads when cranking the engine. A little mark with a Sharpie can be used to set a reference with a new, or at least healthy, battery. We're not so much watching for an absolute number as for a big change as the battery ages.

The gauge will also distinguish a healthy alternator / regulator from a sick one. A reading of 13+ volts is right with the engine running; not too much more than that.