Question about Heating & Cooling
3 lights blinking It means according to codes that there is a pressure switch error. How do I reset this ? Randy
Most furnaces can be reset by turning the power off and back on.
The pressure switch senses pressures in the furnace to make sure the exhaust fan or draft inducer is operating properly. if not the furnace shuts down. check the inlet and exhaust terminals outside for obstructions (I.E: leaves,frost or snow) check the drains to make sure they are not clogged . Hope this helps.
Posted on Dec 30, 2013
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Posted on Jan 02, 2017
Thanks for the carefull description of the fault, The vent system is designed so that if a leak occurs fresh air from the living space will be pulled into the vent rather than dangerous combustion gases pushed out to insure this there is a carefully calibrated -pressure switch that will not allow the unit to fire unless a negative pressure on the vent is proven this can be prevented by many things, here are a a few :a sticky micro switch, a leaking hose from the vent to the pressure sensor, cold stacking in the flu(either a down draft or extremely cold air in vent that restricts warm combustion air from being pushed out), a problem with the power exhaust fan(debris has gotten in the housing preventing an easy start), i usually find the cause to either be a bad pressure sensor hose or debris in ths exhaust fan housing either blocking blade movement or obstructing the pressure sensor hose port.
To clear the fault turn of the breaker to the unit then restart the unit and fallow the sequence of operation to see where the fault occurs the fan should come on first then the exhaust blower should come on when negative pressure is achieved it start the lighting sequence if the lighting sequence doesn't start and you get the same fault take the neg pressure hose loose from the exhaust fan housing and start the sequence again while pulling a slight negative pressure on the pressure sensor with a hand held pump continue this process until you find the fault.
Posted on Mar 11, 2008
SOURCE: The led indicator blinks 3
Pressure switch open. Remove the small hose at the blower assy and gently **** on it. You should hear the switch on the other end of that hose change states. If not then it's the hose (cheap) or the switch (100 bucks but tough to find 2 years ago) or the wiring to/from or the control module. If it does do you have a bunch of white **** (the gasket) coming out of the black blower mount? I had to remove broken gasket and Permatex the seal to create the proper pressure; that's probably your problem as well.
Posted on Oct 03, 2008
Induced Draft Motor Will Not Run
On furnaces with an induced draft motor, the motor must first come up to speed creating a negative pressure for the pressure switch. This switch must only be closed after the induced draft motor comes up to speed or the motor will not start. If this switch is jumpered (bypassed by the technician) prior to a call for heat the furnace unit will give an error code of “pressure switch contact failed in the closed position”. If the motor does not start check for induced draft motor wheel stuck or seized, lack of 115-volts to the induce draft motor, bad start capacitor on induce draft motor, defective inducer motor.
Posted on Oct 27, 2008
SOURCE: Trane Furnace xv-80
check the pressue switch and make sure that nothing is in the fan that would cause it to not draw. I have seen water inside of them at times due to the high efficentcy of the units. let me know if this does not solve it please.
Posted on Jan 01, 2009
If you know where the high limit switch is you can always cut the two wires and wire them together causing the limit to close. But what you have to watch out for is why the high limit is not closing. That means in your return air either you have a dirty return air duct, dirty filter, or you don't have all your registors open to allow the heat to escape the heat exchanger. Just watch over riding the system. The high limit switch should either be on or behind the blower, in the middle of the system right under the heat exchanger. any other questions about hvac just ask.
Posted on Jan 17, 2009
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