How can i fix my Glow Worm 20 - 30F?

The boiler only starts the fan and fires up if i blow into the Air Pressure Switch. The Mid Position Valve and Pump are working. The boiler will run for about 18 minutes making hot water and heating the radiators but wont restart until i blow into the APS again.

Any suggestions?
I would like to get the system working before i sign up for a care plan.