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voltage gauge reading wrong?

dirtdogger17

NAXJA Forum User
hey folks..i recently did the dash swap into my '95 sport..i put in a '92 Laredo full cluster..everything works well but my voltage gauge is only reading at about 11 or 11.5 volts..at the battery its reading 14..its a 4 month old optima red top and the alternator was replaced less than two months ago..is there a bad wire or a fuse i can change or do i just have a bad gauge?..thanks much
 
I don't know that I'd sweat it all that much really. I have always used volt gauages for consistency more than accuracy. If you know you've got 14 at the gauage, who cares that the gauage read 11.5? Just know in your head that if it drops below that then you might have a problem. That's just me....but I am cheap and wouldn't want to fuss with it. I would probably be more worried if the vehicle was some kind of high performance machine. Not to say that your Jeep or mine isn't worthy but.....
 
I've been having persistant charging problems, which is partly why I swapped in this new dash..its just nice to know what its reading at instead of the light that pretty much says "oh by the way..your alternator is toast"..as you come to a bucking stop in the middle of the road..(been there more than once)..is there a way to make it anymore accurate or even close to accurate?..maybe someone has a wiring diagram..?..i appreciate it
 
I'm sorry...I didn't realize you were historically having a charging problem. That makes things different. Disregard what I said then. Wait a while and see if someone else will chime in.
 
That's funny. I did the gauge swap, and only the temp gauge is reading wrong ... it consistently reads up around the redline, even tho I KNOW the motor is running cool and there is no air bubble around the sender.

Perhaps our two problems are caused by the same thing, like a poor ground, or something.
 
Measure the volts right on the battery, then measure from battery + post to
alternator body, then from battery to chasis metal. These measurements should all be very close (like to 0.1 v). If any are different that indicates a ground problem. If you are ok there you might make up some long leads for your dmm and measure from batterey to the ground bus on the gage cluster. If you can find the "+" side of the gage meter measure from there to battery "-" as well.

You probably need the engine running for all this to see the problem.
 
This is a common problem. The voltmeter on my '88 XJ typically reads about 12 when it's close to 14 at the battery. Often the problem is a poor ground from the gauge cluster to the chassis. You might try running a supplemental ground wire directly from the negative terminal on the voltmeter directly to the body, or even directly to the negative battery terminal.

I haven't bothered. I know it reads low, so as long as it stays in the same place I figure I don't have a problem. Look on the "positive" side (pun accidental): if it's out of the red, it'll show red sooner if there's a problem, so you could consider it an "early warning" system.
 
unfortunately im always in the red..im definitely gonna look into running another ground from the voltmeter itself...my temperature gauge is also reading incorrectly (not at all)..could it also be a ground problem?..theres nothing quite like playing sherlock holmes with my jeep problems
 
Before changing or adding anything, use the same "tester" that shows 14v at the battery right on the voltmeter in the dash. If adding an extra ground wire doesn't give you the reading you are looking for then "adjust"(bend) the needle on the dash gauge to match the voltage as seen on the other "tester".
I say this because you are relying on a 2nd source of information the "tester".
 
Temp gauge reading wrong

You do know that idiot lights and guages require different senders, I hope. If you still have the original idiot light senders, the guage will not work.
Rather than jumping into a voltage guage discussion, you may get better info by starting a thread on Temperature Guage conversions......some of us (me) get confused about which we are talking about in some of the posts, once they branch out.
 
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