My 3 year old Amana is giving me some serious issues. I have had 5 servicemen over now who haven't been able to fix it. The problem seems to be that after a successful heating, the inducer blower does not turn off. The unit is then unable to fire again. At this point I get the double blink from the control module that translates to "Low fire pressure switch stuck closed" Any Ideas? Help!
Check the condensate drain, hoses and pump if it has one. Like Drumbanger says, check the pressure switch. Also check the intake and exhaust vent for blockage of water or debris. All water should drain back to the furnace and not collect in the venting. Your furnace has two pressure switches, replace the low pressure switch.
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This is a down flow unit. There is no pressure valve on this unit. Here is all the parts on this unit.
1. Manual - reset, when used.
2. Blower and blower motor
3. Relief box also known as a exhaust flue.
4. Gas valve control knob or electric switch, ON/OFF
5. Gas Valve
6. Gas burner
7. Ratting plate
8. Blower door safety switch
9. Blocked vent safeguard tube and switch
10. Gas Manifold
11. Manual limit switch (2)
12.Hot surface ignitor
13. Flame sensor
14. Inducer blower motor
15. Control board with relays and transformer.
That is all the parts. The first thing the heater gets a call from the thermostat to the control board marked W. The board sends 24v to the inducer fan relay which makes and causes the inducer fan to come on now there is a small tube that runs from the inducer fan box to a switch when the switch makes it sends power to the board which proves you have cleared the exhaust flue then the flat surface ignitor starts to glow and then gas valve opens and fires. now if this tube is stopped up the heater will not fire and will lock the unit out. Also if the flue is stopped up with trash it will do the same thing. If you are not familiar with gas heating units you should call a service company out and check out the system there is a lot of things that need to be checked out every heating season as to keep you and your family safe.
Usually when the Vent or Inducer motor runs all the time
The pressure switch is usually bad
The furnace board is seeing that the pressure switch is open, so it brings the vent blower on to close the pressure switch but the switch being bad won’t close so the furnace board will keep the inducer motor running continuously.
Double check the wiring connections, maybe you have the pilot valve and the main valve wiring reversed. I had a call one time where the homeowner installed the gas valve backwards, so no flow and of course and the wiring on the three terminals was reversed.
The inducer should start whether or not the gas valve is wired wrong, unless it is wired in parallel with the pilot valve.
There are too many reasons for this to happen so we would have to narrow it down. The sequence of operation on a Goodman furnace is usually:
1: Inducer draft motor comes on
2: Hot surface ignitor comes on and glows
3: Gas valve opens, lights burners
4: Flame sensor detects flames
5: Blower comes on
If the inducer motor never came on, then you start looking at power to the unit, thermostat issues, or inducer motor issues. Just a few places to start. Hope this helps!
If you have a code indicating pressure switch thid is 50% of the time the barbed port on the induced draft assembly where the pressure switches tubing connects. Carbon builds up in this port requiring reaming, I use a small drill bit and insure I can feel, sense the blower wheel to insure it is clear, it is easy to be fooled as the carbon is tough at times. If this is not it you have a bad board assuming the pressure switch is closing and opening as it should which can be determined by using an ohmmeter. or voltmeter.
Replacing the board, flame sensor, and pressure switch, and cleaning out the induction motor was definitely a good start. Other things to check would be a blocked or restricted flue pipe, I have ran into a few bird nest before!, and you also want to check or replace the hose that runs from the inducer to the pressure switch if you haven't already. To be honest, most of the time I clear out the nipple on the inducer where the hose goes with a small piece of wire and it works. The last thing I would suggest is making sure the new pressure switch is rated for what you need. Alot of the revisions on furnaces actually call for less than the original pressure just for this problem. Hope this helps and good luck!
An indoor blower running when it is not supposed to usually indicates an overheat condition. I would guess that it has been cycling on and off for some time and finally caused the high limit to stick and not auto reset. if you tap it sometimes they reset. the real problem is that it has been overheating from lack of airflow, over sized unit, not enough return air, too many closed registers, dirty filter, dirty squirrel cage blower and or air conditioner a-coil. If you get it started again sit and watch the unit run the flames should come on and stay on for the entire heating cycle, not going on and off.
I wish I could help you more but it is difficult without seeing the problem myself. Good luck! this should get you started!
If it is calling for heat the draft inducer it is the first device energized, the pressure switch will want to be proved and then the ignitor will glow and the gas valve will energize and the sensor will prove the flame and the heat is on.
If one of the above is not in the right time and place the rest will not work. About the fan it is either a shorted control wire for the fan or the limit switch (the high temperature limit) is made or bad.
If that is not the case the the thermostat has a switch in the back between the gas fired or electric. That will determine if the fan should be on every call for heat.
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!