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Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience:  Manufacture Rep for Major Brand, Technical Trainer, NATE
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Rheem furnace. blower motor runs continuously. thermostat

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Rheem furnace. blower motor runs continuously.
thermostat set to auto. green LED flashing on control panel. 2 flashes pause, 2 flashes pause etc.
furnace electronic ignitor will not come on therefore no gas valve activation.
please send any advice you might.
2 flashes in the control tell me the vent pressure switch is open.

Turn the furnace off and back on. Call for heat.

Does the vent motor come on when the thermostat calls for heat? Does it come up to full speed?

If it does, you may want to pull the little rubber hose from the vent blower to the pressure switch to make sure no water has accumulated in the switch. IF yu get a droplet of water, blow it out and put it back on. (put it back on anyway but blow any water out)

Verify there is no blockage in your vent/chimney

Douglas and other HVAC Specialists are ready to help you
Customer: replied 7 years ago.
did all of the suggestions. blower motor still runs even with the thermostat in the off position.
still flashing 2?
If it's still flashing 2....

Locate the pressure switch. It's a round switch with a rubber tube that goes to the venter motor....(the tube you blew out)...

Take the two wires off the pressure switch and hold them apart. (if there are 3, let me know before proceding). Call for heat and when the venter motor starts touch those two together and hold them and tell me if it starts the ignition sequence.

Customer: replied 7 years ago.
Thanks. had to leave for a while. i will try it and let you know.
Customer: replied 7 years ago.


The pressure switch by-pass did not turn on the ignitor. the vent is clear, and the centrifugal fan is creating lots of air flow. the LED for the "Y" connector is now flashing 3 times and then a pause.



3 times is an open limit switch....

Ok.... Look for one of these... they are small and hidden around the burners, there may be more than one and when you find them, hit the red button. If they are tripped, you will feel it click. they are about this size and have red wires going to them...

Customer: replied 7 years ago.


Checked the limit switch. shows continuity. light pressure on the limit switch disc opens the circuit. Put every thing back together. Still have 3 flashes on LED at "Y" connector and the main blower motor comes on as soon as power is applied. The vent motor also comes on. Shouldn't the vent motor come on first followed by the ignitor and then the gas valve and then the main blower motor after heat is established in the chamber that collects the heat for distribution?

yes, but the limit is open still

On the firewall there is a rectangular limit switch. its about 2" wide by 3" tall. There are two red wires to it. Pull one red off and touch it to the other wire and see what happens. Dont let it touch anything else.
Customer: replied 7 years ago.


We hit paydirt.

That was it.

Everything is working in proper sequence now with that limit switch by-passed.

Is there anything else you can think of that I need to do other than replace the limit switch?

Thank you so much for the expertise and patience you displayed.

You are a credit to your profession.

Thanks again,

Leonard Nunn


No...dont bypass that!!!!

this was for testing purposes only.... If the limit is stuck open it MUST be replaced... This is the final safety between you and a meltdown... Do not leave it jumped.
Douglas and other HVAC Specialists are ready to help you
Customer: replied 7 years ago.

I didn't.

I have already taken it out and ordered one.

I shut the furnace down once I saw what the trouble was.

Thanks again,


phew!... Good... I can sleep better now.