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Bard gas furnace model # H80D36B

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grambo151
grambo151 Member Posts: 7
in Gas Heating
Okay, I just bought this home and I have a 80's model bard gas furnace. There was no thermostat here when I bought it. Recently I bought a new honeywell (cheapest thermostsat available) thermostat from home dwpot. The blower is short cycling and the flames do not kick off when the blower is on. I replaced the fan limiter and the problem went from a 5 second short cycle to the blower to the blower running about 30-40 seconds, kicking off then not blowing again until the temp reaches about 200 degrees on the fan limiter. After that the blower will kick back on for about 5 seconds and I havnt let it go any further in fear of it getting too hot and causing more problems. Thebduct work is clean and free from debris and the thermostat is wired with only two wires for operation. What could be causing this short cycle? Also the other fan limiter that was on before i replaced it was short cycling every five seconds and after the third time it wouldnt run at all. I am at a loss and its been 30 degrees at night recently in west virginia where we live. Any help would be appreciated.

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  • Tim McElwain
    Tim McElwain Member Posts: 4,625
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    How many wires to the original thermostat?
    What is the Make and Model of the Fan/Limit Control?
    Did you check the filter to see if it is clean?
    What is the make and model of the gas valve?
    Does the thermostat you installed have a anticipator?
  • grambo151
    grambo151 Member Posts: 7
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    There was no thermostat here when i moved in. There was four wires coming out of the hole but only two looked like they were being used. I hooked up the new thermostat and everything seemed to work fine but until I actually needed it recently is when i discovered the short cycling blower problem. Not sure what an anticipator is but the honeywell therm is the basic cheapest round style at home depot. The old fan limiter as well as the new one is a honeywell L4064B2210 WITH A 11 1/2 INCH insertion, 3/4 diameter adjustable fan differential. It does have a switch for auto and manual blower operation, but even when i turn the blower to manual op it only runs for a short time and cuts off, but after i turn the thermostat back down (turned off) the blower will kick back on after a few minutes on manual mode. This baffles me because on manual it should run until i decide to turn it off, making the issue even more vague.
  • grambo151
    grambo151 Member Posts: 7
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    Oh the filter is brand new as well. The gas regulator is also honeywell, model VR8200A_2215.
  • Tim McElwain
    Tim McElwain Member Posts: 4,625
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    Is the unit a direct drive blower or does it have a belt?
    Some older motors may require oiling, if they do not have oil they will shut off on an overheat relay in the motor check when the motor is not running to see if it is really hot. If so pull the fan out and look for oil openings on the motor. Use 30 w oil to oil or look around the previous owner may have left oil sitting around.

    I am concerned that the old wiring for the thermostat was four wires and you are only using four. What are the make and numbers on the thermostat you installed?

    Make sure on the fan and limit you installed that it is set at about 140 to 150 fan on and about 110 fan off.

    Is the limit wired for 24 volts or 120 volts?

    Do you have any other switches in the circuit from the thermostat to the gas valve?
  • Tim McElwain
    Tim McElwain Member Posts: 4,625
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    grambo151 said:

    Oh the filter is brand new as well. The gas regulator is also honeywell, model VR8200A_2215.

    That is the gas valve and it is a 24 volt valve. Do you have a multi-meter?
  • grambo151
    grambo151 Member Posts: 7
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    The honeywell thermostat model is CT87N4450. I will go checkbthe typebof blower but i think it is direct drive because i see no visable belts but i will check it out.
  • grambo151
    grambo151 Member Posts: 7
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    Yes i do have a multi meter
  • Tim McElwain
    Tim McElwain Member Posts: 4,625
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    When all this coming on and going of occurs have your meter set to read AC volts and see if you are getting a steady 24 volts to the valve or is it on and off. If you have a steady 24 and the valve keeps shutting off then the valve may be the problem.
  • grambo151
    grambo151 Member Posts: 7
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    This would make the blower cycle as well? The flames stay lit during the whole process and never shuts off. But i will chek it with my meter to see what it is doing.
  • Tim McElwain
    Tim McElwain Member Posts: 4,625
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    If the gas valve is shutting off on limit (200 degrees) then there is a problem with air flow, is the filter clean, how many return ducts do you have, are all the vents open in the house, is the blower getting up to full speed, is the blower blades clean?
  • Tim McElwain
    Tim McElwain Member Posts: 4,625
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    I have to leave you now as the Patriot game is coming up. I will check back later.
  • grambo151
    grambo151 Member Posts: 7
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    All vents are open, everything is clean, the flames do not stop no matter when the blower kicks on or off. It isbthe blower that is short cycling, and the fan limiter only kicks the fan on correctly once during the whole process, the flames never shut off. So what i have gathered is it could be the thermostat wiring, gas valve, or lubrication issue. What I dont get is the fan sounds smooth, the flames keep it hot enough for operation, but the blower kicks off prematurely and will not come back on when the limiter tells it to even on manual mode. I am at a loss and funds are short, hence why I am here. Thanks for the help Tim, hoepfully Ill get it soon enough.
  • Tim McElwain
    Tim McElwain Member Posts: 4,625
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    It may be time to get a pro to take a look at it.

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