Polaris 3900 leans on 2 wheel side. Runs fine without bag.


New member
Mar 24, 2017
Frisco Texas
My 3900, which I have had for 3 years or so now, has been running on it's side about 80% of the time lately and gets stuck by walls where they meet the pool floor. Needless to say, it isn't cleaning the pool bottom like this.

I replaced the ballast float and the backup valve (it was constantly on). I also just replaced the internal drive mechanism with a gen 2 tune up kit. The water management system and the feed hose are from the original.

Wheel rotations are at about 34 rpm.

If I remove the bag it runs just fine. Stays flat on the bottom and does not get stuck on walls. I thoroughly cleaned the bag and put it back on but the issue remains.

Does anybody have any suggestions? I'm at a loss.



TFP Expert
LifeTime Supporter
Jun 7, 2011
Midland TX
Welcome to TFP, and glad you joined us!

I've never had one of those, but people talk about them around here fairly often. Best of luck solving the issue.