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Bubbles17 09-29-2012 10:53 AM

Pressure Switch
I have A Bryant 355MAV Furnace & it is throwing the 32 code Low pressure switch Fault. What do I need to do or check?

biggles 09-29-2012 01:31 PM

if your trying to run the heating that silver round thingy is the pressure switch that OKs the burner after the Induced Draft motor starts to tell the spark ignition/burner air is being supplied to the burner section....remove the orange tube and lightly blow into it should hear i clicking.. sound your simulating the ID fan....that switch has to be in the open position before a call for heat then close from the ID running....NOTE....any time your stat calls for heat the ID is the first item to run on the heating cycle...pressure switch...makes...ignition spark pilot proof ...pilot,main fan....that ID has to run the entire heat cycle any break on the pressure switch the unit will restart the heat call///some units lock out after 3 tries....toggle the 115V furnace switch to clear the latching fault on the control module.....:wink: check make sure the squirrel cage in the ID is clean on the rounds to make that switch...

Bubbles17 09-29-2012 01:53 PM

It is a double pressure switch. I removed the 2 hoses off the back & blew in to them & they both make the clicking noise. What else can I try on it?

Houston204 09-29-2012 07:16 PM

Check to make sure that all PVC pipes leading into the combustion-air intake and vent/
exhaust are free from any cracks and sags. Also check the combustion-air intake and
vent/exhaust pipes on the outside of your home for blockage.

Condensing furnaces will also display a pressure switch error when the furnace drain is clogged.

hvac benny 09-29-2012 07:24 PM


Originally Posted by Houston204
Condensing furnaces will also display a pressure switch error when the furnace drain is clogged.

Also if the heat exchanger is plugged.

techpappy 09-30-2012 10:00 AM

Also you may have to remove the ID Fan to find blockage in the actual fan itself..other recent blogger found that the fan gasket had dislodged and plugged up the fan blades..

Bubbles17 10-01-2012 09:02 AM

The exhaust fan dose blow really good. Where or what is the ID fan?

techpappy 10-01-2012 09:30 AM

The Induced Draft (ID) Fan is on the front of the furnace and exhausts the products of combustion. The fan produces a negative pressure and the pressure switch is thereby activated or the terminals across the pressure switch close thereby completing a circuit to allow the pilot to light, then the pilot is sensed by the flame rod which then allows the main gas valve to be energized and open for main flame. If just the fan runs and nothing else then the you have to make sure the presure switch is activated. Lack of same could be due to lack of negative pressure by the fan or blocked sensing tube. Remove sensing tube to make sure it is clear and that the orifice up inside the fitting is not blocked. Use paper clip or similar device to clean it out then try sequence again. Also suck and blow on tube and listen to see if the pressure switch clicks or is activated. The fan could be running fine but any such blockages prevent air flow or the proving of air flow. Try to sequence furnace on once that is verified.

Bubbles17 10-01-2012 04:05 PM

Also when the inducer blower kicks in the RPM get really high. What would cause that?

techpappy 10-01-2012 05:28 PM

might just sound very high due to blockage...did you take it apart

Bubbles17 10-01-2012 05:37 PM

Yes I took it appart. It is all clear in there. What next?

beenthere 10-01-2012 05:44 PM

Take an amp draw on it while it running. This must be done when its on the furnace and everything is connected back up.

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