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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8682
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Our gas pack furnace will not turn on. When I remove the

Customer Question

Our gas pack furnace will not turn on. When I remove the hose from the inducer fan and blow through it , the furnace works for a few cycles and then stops again. Any ideas?
JA: Did you check the furnace's filters?
Customer: Yes, all new.
JA: Do you plan on doing the work yourself?
Customer: I hope to, yes.
JA: Anything else we should know to help you best?
Customer: I had a similar problem several years ago with a different unit, the inducer tube was plugged and upon blowing through it has worked great since. They are 10 yr old units.
Submitted: 11 months ago.
Category: HVAC
Expert:  Phil replied 11 months ago.

Hello, that is good trouble shooting work you have done so far.

The roundish pressure switch that the tube is connected to probably has a leaking diaphragm in it ...OR... the inducer blower wheel is clogged with soot and not moving enough air through the fire box (heat exchanger)...

Next step will be to use a U tube manometer to check the vacuum on the tube leading to the pressure switch. (the one you blew through) see if the vacuum exceeds the pressure rating stamped on the device. (approximately 0.02 to 0.04 inches water column).