Voltage indicator jumps between 12-18 volts on idle, steady 16v under load.

[tahuds]

The voltage gauge on the dash is jumping between 12v and 18v when idling but with acceleration it settles in at 16v. The difference in voltage is noticeable when idling, as all of the lights, interior, dash, radio and headlamps pulse with the changing voltage.

What could cause this?

I'll post a link to a U-Tube video of it tonight, I just don't have a camera with me.

 

[locovaca]

Might have your voltage regulator going out. When is the last time you replaced your alternator? And how many miles on your truck?

 

[JP02XLT]

Check all the grounds, these Rangers are notorious for bad / weak ground connections which can cause the light dimming your seeing, it is also a sign of the voltage regulator on its way out, as was previously mentioned.

JP02XLT

 

[tahuds]

Might have your voltage regulator going out. When is the last time you replaced your alternator? And how many miles on your truck?

It was the voltage regulator, I replaced the alternator and it was fixed.

 

[adsm08]

It was actually probably the rectifier. But that is part of the regulator.