Well, I have been fighting a low battery problem all winter, I figures it was due to the extreme cold we have been getting here in Michigan. I replaced battery and the battery light on the machine still comes on as Iam driving. The last trip i took drained the battery enough to have to pull start it to get it back to the trailer and along the way lost a ton of power and started to backfire... I finally limped backed to the trailer after the temp light came on a couple times. A few days later I finally had time to mess with it and it ran fine (after putting it on the battery charger). I assume the backfire/power loss is all caused to low amps due to the battery not charging?? I tested the battery with a multimeter ( never really used one) but it read just under 13amp with machine not on, I started machine and ran it at about 2-3000rpm and the amperage never moved.... Where do I start? rectifier or? I hate to throw parts at it obviously... Thanks for any help!!!!!

 

9 out of 10 times on battery problems the ecm module has shorted out.Controls charging,fan operation along with having internal circuit breakers. Wasn't on the recall list,but should have been as I've changed several on the 330 Trail Boss and Magnum 330s.Item #29.Part# still shows the same here and on the Polaris website. If changed you would be sent the updated one. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse
Huge ATV Recall by Polaris - Sportsman and Scrambler

 

Thanks for the reply!!! I know there probably isn't anyway to test the module without taking it to a dealer so I guess Iam gonna have to try to replace it and see if it works....Thanks a bunch!!

 

Easiest way is with a good battery just check what it's charging at the battery terminals at an idle. Should be at least 14 volts. If not,then most likely the ecm. Here's a pic from a member that had the updated style USA made Sure Power ecm that melted inside. Doesn't matter if they're Chinese like the original ecms or USA made,they all can fail.

 

I checks the volts at the battery with the machine off and it read just under 13. With the machine on the volts never really moved they stayed under 13 at idle and at a higher rpm. So I guess Iam gonna replace the ecm for sure. Just hesitant on throwing $200 in parts at it without knowing 100% that is/was the problem.... Thanks for your help!!!

 

Not enough voltage plus factor in things such as lights or any other aux equipment and the battery is slowly being sucked down. You can get this cheap 5 buck manual and do an ac test on the stator or the "break even" test that's listed in chapter 10 to be sure it's not stator related,but most of the time it's either the battery or a faulty ecm. The low battery warning light tells you something is wrong. 2004 Polaris Magnum 330 Service Manual PDF Download

 

it did turn out to be the ecm. swapped it out for a new one and all is good

 

Wondering if you found the problem. Shame that Polaris didn't include all the Chinese ecms in the recall including the 2004 Magnum/Trail Boss 330 as they knew all of them were bad.. Huge ATV Recall by Polaris - Sportsman and Scrambler