Propane Generator Problem?

[Okieboy]

Onan 5500 Propane generator will run on one of the two propane tanks but not on the other one. Both tanks are full. Why? It will start and then dies on one but runs fine on the other tank.

[wingnut60]

Well, first thing I would do is reverse the tanks and see if now the good one won't work...
Sounds like maybe the regulator is not allowing a switchover, or maybe there is a problem with the valve in the tank that is not working.
Are you using the regulator valve to switch tanks?