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disan varela Posted on Jan 17, 2019

C8mpn075b12a1 inducer fan runs constantly replaced smart gas valve sv9541m2094 and circiut board with universal board st912bu. called honeywell tech support n could not help me.

Checked high limit n roll out switches all good pressure switch good as well.

5 Related Answers

Anonymous

  • 89 Answers
  • Posted on Nov 01, 2009

SOURCE: I 've got an Intertherm G3RA-072A-13. It has a

You have a limit switch open. See if you can see any little button switches with 2 wires going to it, check all these for continuity

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Anonymous

  • 1515 Answers
  • Posted on Jun 06, 2010

SOURCE: TROUBLE REPLACING OEM TIMER - UNIVERSAL ELECTRONIC FAN TIMER

Hi, you should be real close with the universal timer and the factory OEM. On the new control board, if you have 24 volts to the board, you should have 24 volts from R to ground or to Common. I know that on most all control boards the voltage in is 120volts as you will have terminals for L-1 and L-2 to run the high voltage controls from the board and all of the thermostat control terminals in a row, R,G,Y, W, C, and so on are 24 volts. 120 volts is stepped down to 24volts control and you say you have nothing out. Make sure you have 120volts in. You are calling this a timer board, is this a heat-pump defrost board with the 3 settings and pin to defrost the unit at 30,60,and 90 minute times? This is what it sounds like. If all was terminated per diagram, you would have the 24 volts required to fire this unit. These defrost timer boards require high voltage to them as well. Even though the board is a new board and you know for a fact that it is wired properly, it may be a defective board. I have seen this many times in my years as a tech. I have shorted new boards out by static electricity and by mis- wiring one. You can kill power and look at the back side of the board to see if this has happened. Sometimes you will find that they missed a solder point on the back side not completing a circuit through the board. To give you more ideas, I would need to see the diagram, or if you could send me the model, serial, and name of your unit. The board number would help also. Check out what I have said and get back to me on this. I will wait to hear.
Shastalaker7

bobicehouse

Robert Moller

  • 1524 Answers
  • Posted on Nov 04, 2010

SOURCE: inducer fan on my gas furnace is constantly

Bad lock-out switch

Robert

  • 1036 Answers
  • Posted on Mar 08, 2011

SOURCE: Gas furnace with Honeywell smart valve code error

Hello, it sounds like your Furnace might be shutting off due to your high limit switch.A limit switch will open when the furnace overheats due to low airflow, . check air filter, clean blower wheel, and check to make sure the blower wheel is running at proper speed and not dragging sometimes cause by a weak capacitor. Anything that restricts airflow will cause a limit switch to open.

Robert

  • 1036 Answers
  • Posted on Nov 24, 2012

SOURCE: no power to gas valve

Have you checked the wires from the board to the gas valve? You should get 24 volts after igniter glows.

Testimonial: "Found out I have a craked heat exchanger which melted a wire to the limit swith! I was testing the furnace not being hooked up to the duct work which worked fine after I repaired the burt wire, but when I hooked it to the ductwork that is when the cracked exchanger became evident!"

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My Honeywell smartvalve stop opening the gas valve, inducer motor started, glow and pilot happen, just no fire...I replaced said smartvalve and upon installation, the inducer motor wouldnt run, no glo

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.
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Have you checked the wires from the board to the gas valve? You should get 24 volts after igniter glows.
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My Furnace does not turn on. Installed a new igniter/flame rod assembly, still not coming on (I had this same problem before with another furnace which I changed the igniter flame rod and problem was...

Assuming the inducer fan and pressure switch are working fine, your next step is to test the voltage coming to the gas valve. There should be 4 wires going to the gas valve, one is black. This is the 24 volt power side. Unplug the molex connection at the gas valve and while the inducer is running test for 24 volts AC. If you get voltage you have a bad valve. If no voltage you have a bad circuit board. Test the safety circuit and roll-out sensors to make sure all switches are closed. Check for continuity across the switches.
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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.
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