Old ICP furnace, pressure switch code

Old 04-23-15, 05:29 PM
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Old ICP furnace, pressure switch code

ICP gas furnace

Light flashes 3 time: pressure switch stuck open. DMM reads that the switch is closed. DMM shows 24v going into the pressure switch to the blower and into and out of the high temp switch. Furnace will not heat with the pressure switch disconnected or with the wires shorted.
Pressure switch is operational, but not tested with hydrostatic pressure meter. Im thinking its the White Rodgers control module.

Ive exhausted all of my handiman ideas for trouble shooting. Any suggestions?
Old 04-24-15, 02:18 PM
Join Date: Nov 2012
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When I test the safety's, I put my meter leads across the pressure switch so I can see 24 volts when the switch is open, and nothing when the switch is closed. You shouldn't read anything across the pressure switch once you hear it click!

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