Question about Goodman GMS90703BXA Heater

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If the pressure switch fails to close is this because of a bad switch or inducer fan motor? goodman model gmp100-4

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Do not assume that the pressure switch is bad nor the vent motor. The first thing to check is the vacuum hose from the pressure switch to the vent motor. Sometimes they get moisture in them and sometimes they get clogged in the start tube on the vent motor. Take a small needle or paper clip and clean out the start tube on the vent motor. Check the hose for dry rotting or leaks. Cut the ends back about an 1/2" if you have enough hose extra and then re-connect. Next step is to check your flue pipe for a restriction like a birds nest or a wasp nest in the outside termination point. Then to eliminate the vent motor from the equation, take the vacuum hose off the vent motor start tube and with the furnace calling for heat , **** on the hose to keep a constant vacuum on the pressure switch. Watch the ignitor glow or spark ingition start to spark. make sure it lights the burner runners and all burners are lite. usually the ignitor is on the first burner and then there is a flame sensor on the last burner. If the flame does not ignite to the last burner the flame senor will kick tell the control board to turn off the gas valve and shut down. If this happens pull the flame senor out with a 5/16" nut drive and clean lightly with sand paper and re-install it. Start the process over and you should have sucessfully fixed your furnace. If the constant vacuum does not bring on the ingnitor replace the pressure switch.

Posted on Nov 19, 2010


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2 Answers

Goodman furnace has a solid red light, but the inducer is not starting up

The inducer motor would run until the heat shut off .if pressure switch is closed and all other safety switches close your furnace should fire up

Oct 25, 2018 | Goodman Heating & Cooling

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Why does inducer motor run nonstop on goodman furnace?

possibly a board issue does inducer shut off when no call for heat

Jun 12, 2015 | Goodman Heating & Cooling

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Problem with furnace not kicking on.

could be one of a few diff issues. firstly, the air pressure switch may be failing. check to ensure the inducer motor is providing enough air flow for the air switch to close. if inducer motor isn't creating enough air flow the faults is within the motor. If the airflow is enough, then fault maybe the air switch. you also need to check for any blockage in the exhaust. ensure no debris is blocking the vent going to outside

Jan 21, 2014 | Goodman Heating & Cooling

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Problem: Pressure Switch Failure to close


The t-state set to fan "ON" will only cycle the fan to turn on only nothing else. "Auto" is where you always want the t-state on when you want to have heat and have the fan cycle off automatically after the t-stat has reached set point.

As for the press switch, there can be two things that will cause the pressure switch not to close. 1: obviously the switch itself and 2: the inducer fan, this has the rubber tubing that connects to the pressure switch.

When you call for heat, the inducer fan ( small fan with black plastic piece that spins ) is the first to turn on, this fan makes sure any left over exhaust air/gases are vented out before the burners turn on, it also stays on the entire heat cycle to exhaust the gases. The pressure switch needs proof of air so the pressure switch closes with the vacuum that is being created by the inducer fan in that rubber hose that is connected to the pressure switch. This allows the furnace to know " my induce fan is working, lets proceed".


I would make sure your inducer fan is working. if you don't see it working then I recommend using a multi-meter ( VAC setting) and checking that you have 120volts supplied to the inducer fan. if you don't, then you need to work backward from there and see why you don't. If you do verify 120volts at your inducer motor, then more than likely it failed and will need a new one. Witch out this, your pressure switch wont close.

If your inducer fan is working fine then make sure you have 24vdc across you pressure switch (again with a multi meter but with VDC setting not VAC). 24vdc in and 24vdc out. If you only have 24VDC in but not out, then you pressure switch may be stuck open. ( This is if your inducer fan is working properly).

I hope this helps. Sorry for the long response. I just don't like people changing parts and wasting money.

Sep 28, 2017 | Goodman GMS90703BXA Heater

1 Answer

Pressure switch goodman furnace 100-4 blinks three times, installed new switch still wont start.Also does inducer motor start before gas fires??

2nd question first here: Yes, inducer motor (exhaust fan) must run before gas an fire.
I'm going to assume you can operate and understand a VOM, as well as being able to observe the proper safety procedures for performing service work.

In the case of a control board returning an error code for a failing pressure switch, but the pressure switch actually checks out OK, try this:

Test your exhaust fan power leads for power coming in from the board during the first few seconds at the start of the heating cycle. If power is not showing up there, there is likely another circuit malfunctioning somewhere preventing startup. However, if power is showing up there, then deactivate the system and disconnect the exhaust fan power supply leads from the motor. Test the motor's coil for continuity - a failed exhaust motor coil will result in no vacuum for the pressure switch, hence no heating cycle allowed by the control board.

In my case, the exhaust fan actually failed due to a broken coil lead at the binding post to the push-on connector. I was able to repair the coil lead myself - at no cost - hurray!

Oct 20, 2011 | Goodman GMS90703BXA Heater

1 Answer

Model a36-15 - heat should be on but as the unit goes on and off sometimes the air blowing is warm and sometimes not which then takes numerous on/off to reset

This furnace has an induced draft motor and a pressure switch that has a tube that atttaches to the induced draft housing where it can sense the pressure or vacuum of the inducer motors running, thus proving to the system a induced draft exists with a purge period followed by a trial period for ignition, (either spark or hot surface ignitor) if the pilot is established another type of flame sensing device peoves a pikot flame exists allowing the main burners to run.

the pressure switch , its tubing and the orifices the tube attaches to piug with carbon or collet moisture if the tubes routed with a dip where condensate c an build and eventually block the ability of the presssure switch to sense the indicers operating, it can fail to close or waver open and closed back and forth as yours may be.

Dec 27, 2010 | Goodman Heating & Cooling

1 Answer

My furnace isnt working the trouble light code says pressure switch stuck open or closed

The pressure switch, open or closed depends on the induce fan motor. the switch could of failed. Try blowing into it, in and out. And or your induce fan motor is not blowing out the excessive heat out of the furnace properly. We provide repairs in the So Cal Area.

Oct 07, 2010 | Heating & Cooling

1 Answer

GOODMAN Air & Heating unit installed. After one and half year the heater would not egnite. Exhast fan starts but no ignition? Can anyone help?

either the pressure switch is not closing (probably clogged) or the ignitor is bad.

Verify that 24 v is coming out of the pressure switch, after the draft inducer motor comes on, then look for the ignitor to glow.
Do you see the glow from the ignitor? If not, replace it.

Jan 30, 2010 | Goodman CLQ36AR49 Air Conditioner

1 Answer

Heat not coming on carrier gas pack code 31

code 31 indicates pressure switch did not close or reopened during the heat cycle....1st thing to check is the inducer motor,,this is a small motor that turns a small blower wheel that draws the exhaust gases through the furnace and blows them into the vent pipe....1st locate the inducer assembly,,most easily identified by the small plastic fan blade that cools the inducer motor as it runs..1st turn off tstat and turn off furnace power switch..then turn on furnace switch,then set tstat to heat,set the temp above room temp by 5 degrees...remove the furnace front cover,locate the inducer motor,,if it isnt turning,but is warm or hot after a minute or so,likely the inducer motor is bad..if it isnt turning and isnt warm after 1 minute,then likely the main control board is bad,,not turning the inducer motor when it should,,,,,if the inducer motor is running,,then the pressure switch isnt closing,, could be a bad pressure switch but more likely there is a problem with the venting...some possible problems that would cause the pressure switch not to close in an 80% eff furnace [metal vent pipe] are: [1] a blockage in the vent pipe,base of chimney,dead bird at the furnace where vent connects to furnace or down inside the inducer assy,accessed by removing vent pipe from furnace....if all clear the chimney could be blocked up inside,,is the draft good when vent is removed from base of chimney?..if furnace is a 90%+ type [pvc plastic vent pipe],,then check the intake pipe at the furnace by removing it where it attaches to top of the intake clogged with anything?..then check the intake and exhaust pipes outside for blockages,,including ice/frost/snow at the exhaust pipe outlet..

Jan 26, 2009 | Goodman GMS90703BXA Heater

5 Answers

Goodman furnace I think

Ok, a flashing 3 on a Goodman control board usually means that the pressure switch is tripping. A few things will cause this. One being a restriction in the exhaust or combustion air inlet. The second could indicate a faulty inducer blower motor and the third would be a blocked or bad pressure switch.
With the front cover off and door switch taped down, Have a helper turn the thermostat up to 75. You will be watching the circuit board for flashing lights and in a few seconds the inducer motor (the small fan hooked to the exhaust) will start. If this does not happen, we either have a bad circuit board or blower motor. If the fan starts rotating, inspect the hoses going to the small circular pressure switch. Sometimes they may get either water or debris in the hose and not allow the switch to sense pressure. If the hoses look OK, the igniter will glow an orange color and you will see this if you look thru the small viewing port. IF no glow, you could have a bad pressure switch, a bad ignition relay (found on the circuit board) or a bad igniter. OK so if the igniter glows, a few seconds later the gas valve should click open and send gas to the burners. The orange will turn to blue. If this does not happen, you have either a bad gas valve or bad circuit board. Finally if you get flame but it will not stay lit more than a few seconds, you may have a restriction in the burner gas train, a bad gas valve, a dirty or bad flame sensor or not enough gas pressure.
Knowing the sequence of operation will give you the needed information to talk with a service technician and cut down on diagnostic costs.
Try looking on the back of the furnace access panel for both model number and a diagnostic schematic. This will confirm what the flashing 3 code means for your unit.
Sorry, without knowing the model number, this is the best I can do for you. Good Luck!

Oct 28, 2007 | Goodman GMS90703BXA Heater

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