Hello everyone. I have an 03, Rubicon 500FA. I'm on my 3rd battery in 30 months. The first 2, I thought were cheap batteries but when the new Yuasa died after 2 week I realized I had problems. The battery does not appear to be charging when running. I started using a battery tender to ensure that I had a full charge after leaving it unused for a week or so. The battery shows 12.8v in off and it drops to 12.4v when I crank it an rev it up. If I turn on the lights is drops to 12.2v. Does this mean that the Alt/stator is bad or Regulator/rectifier? How can I check these 2 parts to make sure?

In addition to the above, before I put in the new battery, I cranked the ATV using a portable battery booster. It cranked right up but the display unit was completely out; no power. The lights work and everything else but no display. I checked all the fuses and they all look good and there doesn't appear to be any corrosion in the fuse box. There is corrosion on the solenoid behind the battery but it starts fine.

I appreciate any help or feedback. Many thanks.