Janitrol Heater Question

[BGFYankee]

Janitrol Heater Question on PA34. I seem to be able to reliably get my B3040 heater to function on the ground, but once I climb into the air, the hot air stops coming. Anyone else have an issue and give me a place I might start? I can verify power is going to the unit and that the blower works. As I said, it's heating on the ground, so I know it's at least getting enough fuel and spark to function there. I'm tending toward the air pressure switch being the culprit, but wondering if there's an easy way to test it...

 

[aerosputnik]

 

[BGFYankee]

 

[BGFYankee]

 

[mrettler]

 

[BGFYankee]

 

[hindsight2020]

 

[Avidflyer2]