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Old 12-27-2011, 10:25 AM   #1
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Gas Furnace Troubleshooting: Pressure Switch stuck on


Dear all,
One of my two furnaces is not working two days ago. I saw three flash light which indicates pressure switch stuck on. I took off the hose connecting draft inducer motor and pressure switch and use a thin stick to go through from one end to another end. I also used the thin stick to insert into the hole on the draft inducer motor where the hose is connected to. The purpose of doing this is to try to get rid of the blockage in the hose and motor. After that, I turn on the power, the furnace worked magically again. However, after 1-2 minutes, the furnace stopped working and the gas light turn off again. Since my furnace can work again, it indicates the hot surface ignitor and pressure switch and motor are all working properly. The only thing I can think of is to clean the blockage in the pipe and flue. I am not sure how to do that.

The furnace image can be viewed here at
http://www.flickr.com/photos/2819369...in/photostream

Label A is where I insert the thin stick to the motor exit and also the hose end.

Question:
Do I need to take off all these screws (B,C,D)? For screw at D, there are two screws on the sides which need very short screwdriver to do that, it connects the motor with the pipe to the roof.

Thanks!

Roy

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Old 12-27-2011, 10:49 AM   #2
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Gas Furnace Troubleshooting: Pressure Switch stuck on


excellent picture and diagram Roy, remove all the screws at level B, including level D do not remove the screws at level C. but before you do all of that try a unfolded paper clip into the connection at A, thats were they usually get blocked.

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Old 12-27-2011, 11:10 AM   #3
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Gas Furnace Troubleshooting: Pressure Switch stuck on


Thanks for your suggestion, Harleyrider.

I used an unfolded paper clip and inserted all the way to the connection at A. I felt some resistance but tried to go through it. I think the clip can touch the fan blade or something else inside the inducer. Put the hose back on and turn on the power. The furnace is working again. This was done ten minutes ago. It is still working and I can see the temperature on downstairs thermostat is going up. I think the furnace works properly now. But I wonder if the same problem happened again, should I just do what I just did or unscrew B and D to clear the blockage? It seems I need a very short screwdriver to unscrew D.

Thanks!

Roy
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Old 12-27-2011, 11:31 AM   #4
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Gas Furnace Troubleshooting: Pressure Switch stuck on


yes, eventually it will build back up, its from the by-products of combustion, and a semi cool stack, it cant be avoided.as far as the screws on the D level, you can leave them in and still take the motor and housing off..........by removing all the screws on B level.I think it would be a good idea to remove it so that you can get a better idea of whats going on inside the assembly. You will need to re-seal it, and you can use high temp silicone RTV, must be rated for 400 degrees and up . Its red or orange in color, just a small bead all the way around.
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