AS an owner Of a 2001 Georgetown Class "A" MH, I follow these postings very carefully, and it has been a great help. I am writing this post, to hopefully help someone else. My jacks are 310 series Kick down/spring return type. For over a year, and several visits to service facilities, I have always gotten the same answer. " You have a bad solenoid and it should be replaced" Knowing that a new solenoid is around $200, and having tested mine several times to be OK, I learned to live with it. After all, it sometimes would extend. Yesterday, while deploying jacks, I noticed that the left rear, the problem one, did kick down, but slowly retracted when I let go of the button. BINGO, there must be a leak. And so it was. Each solenoid has it's own check valve. Sure enough, I unscrewed the check valve and found a damaged "O" ring. Replace it and the jack works like new. Total cost= 10 cents. Total repair time= 10 minutes. ...Advice, buy a box of assorted "O" rings and keep them handy.