2010 420 Rancher not charging the battery
So this has been going on for a while. I have changed to a brand new battery, and it is still not charging. I got the service manual, check all 3 yellow wires coming from the alternator, they check out good according to what the manual says. Checked all wires at the 5p plug between the alternator and the rectifier, they checked out ok. Heres the part where I got to and stopped and have a question. All wires going to the rectifier checked out ok, except the red wire which comes from the battery. The red wire is showing voltage, but it is showing negative voltage. And yes, i double checked the contacts on my multimeter to make sure red was positive and black is negative, and when i checked the positive and negative on the battery, i get positive voltage. So when i connect my red from my multimeter to the red wire in the rectifier plug, and touch the black wire to ground from the multimeter, i get negative 12.5 volts. Im thinking this is a problem, but not sure, and if it is a problem, what are my next steps to solve it so that I get positive voltage?