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Old 12-04-2006, 04:50 PM   #1
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weatherking furnace blower runs continuously


I have a weatherking (made by RUUD) furnace WGPAH and the blower runs continuously. I have turned the thermostat off and it still runs. I watch the start up sequence when I call for heat. The IDM runs and it appears that the pressure sensing switch activates after 20secs. I do not seems to get 120 v at the igniter in the next 30 secs as I should.
Are there any other switches I should check. It looks like it might be the control board but I want to check all else out before getting it replaced as it is a pricey item. As I said the IDM and blower run continuously any time I put power to the furnace even with the thermostat switched off.


Last edited by rayborj; 12-04-2006 at 06:13 PM.
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Old 12-05-2006, 10:03 AM   #2
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weatherking furnace blower runs continuously


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Originally Posted by rayborj View Post
I have a weatherking (made by RUUD) furnace WGPAH and the blower runs continuously. I have turned the thermostat off and it still runs. I watch the start up sequence when I call for heat. The IDM runs and it appears that the pressure sensing switch activates after 20secs. I do not seems to get 120 v at the igniter in the next 30 secs as I should.
Are there any other switches I should check. It looks like it might be the control board but I want to check all else out before getting it replaced as it is a pricey item. As I said the IDM and blower run continuously any time I put power to the furnace even with the thermostat switched off.
I have no experience for your particular furnace but am aware of a situation that can keep fan blower on.On the fan limit switch some have a button that protrudes through the metal case that if accidently pushed in makes the blower run continuously just as if you flipped the switch on stat to have fan run continuously.
This would keep blower running as long as there is power to furnace but should have no effect on anything else!

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Old 12-05-2006, 01:52 PM   #3
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weatherking furnace blower runs continuously


rayborj vbmenu_register("postmenu_25846", true); , I'm experiencing a similar problem.

I have learned that on my Rheem, the microprocessor checks for safety conditions at different times. Not only it checks for the flame to be present, after igniting it, but it checks for the flame sensor to show continuity before flames are present.

If the excess temp sensor is open or the flame sensor is open in the early part of the power up sequence, the furnace will abort power up sequence and the blowers will run continously.

If excessive temp will trip the "round" sensor and open the circuit later on, it would also stop heating as well.

In other words, it appears that the microproccesor checks that the sensors are closed when they are supossed to be closed (before powering up) and open when there is a malfunction.


You asked:

Are there any other switches I should check.

I think that the easiest way to check the "excessive burner area temp" sensor is to measure voltage across its terminals. (In my furnace, there is another sensor which measures air temp @ the plenum area) If you measure any voltage, that means that the sensor is open and needs to be resetted or replaced. I'm referring to the round sensor near the flame area which could be resetted by pressing the bottom. (Not the flame sensor)

Just be aware that 110 volts are present in the area, be careful.

On my furnace, the flame sensor was open all the time. I shorted the terminal to ground and the furnace will then continue the power up process, turning igniter on and gas valve on. However, because the flame sensor is not just a simple on/off switch, and the microprocessor expects certain resistance to ground and I merely put zero resistance to ground, the furnace stops after a few seconds of normal operation.

My present problem is explained under another thread, posted at 8:46 PM PacificTime Monday "Furnace power up problems" It was read but I didn't get any responses yet.

Hope my explanation fits your furnace and your problem.

Good luck, Abel
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Old 12-05-2006, 02:03 PM   #4
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weatherking furnace blower runs continuously


Hi raborj

You have a limit switch open, more than likely it will be the one in the middle of the furnace. This limit switch is about 2" x 4" and has a single screw on top and bottom. Use a voltmeter and check across the terminals. If you show voltage with the thermostat calling for heat the limit is open. Your particular furnace could also have a thermal limit for a rollout limit. Use the same technique to check all limits. If you have a bad thermal limit you have to replace it. Let us know if we can help you further.

Good luck
Rusty
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Old 12-08-2006, 02:23 PM   #5
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weatherking furnace blower runs continuously


The symptoms made it look like the board. However, when we went to look at replacing the board we noticed that the connector with a bundle of wires leading to the board appeared to be a liitle loose. We reset it and voila, the problem disappeared. Advice is to check connectors before replacing board!!
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