Technical Tip Pressure Switch Failure, here is a tip or a trick
I learned when I was in the field working on pressure switches is take a suction bulb that's used on babies
and lightly blow and suck on the tube going to the switch to exercise the switch and it may stay working for a short time but once the pressure switch starts having problems you're getting to the end of life of that switch and needs to be replaced. This is also used to test the pressure switch, using your continuity tester you can see if the switch is making contact when you put pressure or suction on the switch, It a very cheap tool to have on board the repair truck as I have used it many times, It also works good to get trapped moisture out of the tubing on the furnace, or blowing out pilot lines and gas orifices.
Darin DeVries - Author, entrepreneur, e-Commerce
Coleman HVAC Parts