Voltage guage fluctuation issue.

[TheVaderRanger]

Ok, so i just moved to Kansas to go back to college, and my older brother granted me holy permission to drive the ford ranger he has had for the past 2 years now and has completely redone the suspension on, anyway, its been having this issue where even when sitting still the voltage gauge will fluctuate, and gets much worse going down the road. We are both unsure what the issue could be. We have deciphered that its multiple possibilities. Such as, the command wire from the alt. the multi function switch or a short somewhere in the cluster. It had a sound system in it that he removed at my asking, we also believe that may have fried something. Multiple voltage drops have been done but nothing shows us what the issue could truly be. So, what I'm asking is, has anyone else had this issue before? if so what was the fix??? It has a 4.0 mated with a 5 speed. Thank you all ahead of time for the information.

 

[RonD]

Start engine and put a volt meter on the battery, see what voltage is doing.

Should be above 14volts but below 15volts just after starting
After running for a few minutes voltage should drop down to 13.5v, approx.
It should be steady voltage, for either
Rev engine and hold it at 2,000rpm, voltage should go up, then drop down to 13.5v again

If voltage is jumping around, then check voltage gauge in cab to see if it is also jumping around, then shut off engine
Unplug the 3 wire connector on the back/side of alternator, this turn alternator off.

Restart engine
Check battery voltage again, should be a nice steady 12.5volts, approx., no jumping around.
Also check Voltage gauge in cab, see if it is still jumping around

If so then voltage regulator in alternator is bad, replace alternator.

 

[twfmvm]

Check the stator wire connector on the alternator (hidden below the three wire connector mentioned above). On mine it was causing the exact same symptoms. I cut off the stock connectors that were wiggling around and soldered a wire straight to the male plug on the alternator and stuffed the gap with electrical tape. Have had steady voltage ever since.