My IVP door pump stays on continuously at FL200 and above.

History:  I replaced the door seal 3 weeks ago after a leak developed at the seam.

Checking the system for leaks reveals none.

Flights below the flight levels are normal.  The pump comes on occasionally and turns off in a few seconds.

The first time going to flight levels after the new door seal is installed and the pump ran continuously.  At my destination, I soaped for leaks and none were found.  I removed the connection of the seal to the brass fitting, reseated it with soapy water and put a tie wrap around the connection.  On the return trip, the door seal pump ran about ½ of the time. 

I removed the fitting to seal connection and reinstalled it with silicone and another tie wrap.  The pump again ran continuously.  I lost partial cabin pressure after about an hour and landed in Boise and finished the trip on Delta.

The pump still runs and pumps up the seal.

I have not had an opportunity to trouble shoot it again.  I will as soon as I retrieve the plane and return home.

Any suggestions as to culprit?  What to look for?

Suspicions: 1.  It is really cold up at the flight levels and the check valve or the pressure switch is freezing.

2.      I have a leak somewhere which does not show up on the ground.
3.      The pump can’t pump enough pressure to turn off the pressure switch, but why only at altitude?

Any help would be appreciated.

Thanks,

Carl Cadwell

N25CL, 530 hours