Question about Honeywell L4064B2236 Fan/Limit Control Heater

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Fan cycles on and off to often the burner stays on and the fan cy

I turned the fan to on position on the TS and watched the burner it stays on until temp. in house is reached then it turns off.
If I put the TS in auto position the burner comes on but the fan cycles every 30 to 40 seconds?

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  • verilog Mar 11, 2009

    I have the same issue. It has gotten worse throughout the winter. I have an older Ruud 80 heater. The heater fan control unit has a dial that rotates to an "on" position for 10 to 15 seconds, then snaps back to the off position. This will continue without stop now. The switch will not stay on. I am also using a Honeywell digital thermostat. Is this a problem with the heater fan control unit? A mechanical problem maybe? Thanks for any responses.


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What is happening is that the heat exchanger has to get to a certain temperature before the fan comes on that way you have warm air blowing out of the grilles and when the heat excahnger gets cool it shuts off until it warms back up again.

Posted on Jan 25, 2009

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1 Answer

Fan cycles after burner stops

When your furnace has reached desired temperature the burners will turn off but your fan will continue to blow for a couple of minutes Or in other words until it cools your fan limit switch. This switcheck is what tells your blower motor when to kick on and when to kick off.

Mar 06, 2015 | Heating & Cooling

1 Answer

Lennox furnace model G11Q3-110 v.2 burners light but go out before fan comes on

Troubleshoot an ignition problem on a Lennox gas furnace ...

? 2:44
Nov 17, 2012 - Uploaded by grayfurnaceman
This furnace should light its pilot with a spark then the pilot proves its on ... Troubleshoot an ignition problem on a Lennox gasfurnace .... Pilot and no inducer but is the same model as that great video! ... You probably have dirty burners. ... How do you know spark module is not sending 24 volts to mv and pv ...

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Nov 19, 2012 | Heating & Cooling

1 Answer

Janitrol GUPS075-3 Furnace burners will not stay lit

The first thing I would do is make sure the flame sensor is clean, this is a metal rod immersed in the burner flame on the opposite side of the igniter. If too much oxidation builds up on it, it will not allow the burner to stay lit. To clean, just turn off furnace and remove flame sensor and clean with steel wool and then reinstall. If this does not solve the problem there may be a problem with the gas valve.

Nov 08, 2012 | Heating & Cooling

1 Answer

Fan staying on at all times brivis tek304

this means a limit switch is open, or the thermostat is set to fan on, as opposed to "auto".
Unplug the unit, then plug it back in and watch the sequence.

If it goes through it's normal operation and then the burners shut off, it means the high limit has been triggered. usually this means the furnace is suffocating, remove your filters and try again.
If it works fine the second time you just need new filters. if not then the high limit is bad.
The high limit is inside, near the burners on the back wall connected to 2 wires.
it's easy to replace, order a new one (be sure to get the right temperature setting, it's on the old one). pull the old one out and plug the new one in. the wires don't have sides as long is one is in Common or C, and one is in NC.

If the main fan comes on first and the furnace does not cycle, it means a limit is open (or the thermostat is in fan on mode). The rest of the limits are on the same circuit as the high limit, trace that circuit and push the button on each switch along the way, if one clicks you know you've reset it... you also know that it has been set off, which implies a safety hazard and technically you should call a pro to come see it.
Anyway, continue along the circuit checking each one until you've come to the main circuit board. then plug the furnace back in and watch it go. if that hasn't fixed it, call a professional.

May 06, 2011 | Heating & Cooling

1 Answer

The heater heats up, the blower comes on for a minute then goes off, and continues to cycle like this

Good Morning, So, you say the heater does heat up, the fan will cycle on and shuts back down in a minute, and continues to cycle this way. A few things that will cause this. But let me ask this first, does the burners stay on through this short cycling of fan? Let me know if we don't solve it before that. I don't know if you're t-stat is programmable or a mechanical? Anyway, you have what they call a heat anticipator on stats which will cycle unit on and off like this if they have burned out. If it is a mechanical (mercury switch) type, pull the cover and you will see a small dial with numbers and a arrow on it. Set it to .4 and if its programmable, you will have to go into the program to do this. Normally it is set at factory to .4 amps and the setting varies with the amps on the gas valve as they should match. I assume you have been there for sometime and this problem has just started.I wish I knew if the burners were shutting off when the fan cycles off? This would be helpful. If the burners stay on because the fan is only off for a short time, the high Limit switch is good, because when the burners are on, and the fan comes on and shuts off and stays off, the unit will open the contacts on the high limit and shut burners off for safety. I would say that the combination fan control is sticking or failing causing your fan to short cycle. Only, if this is an older furnace though. If it is a newer one with the electronic pilot ignitor, the main control board is you're problem and will need R & Ring. Please get back to me and give me the information I have mentioned, as name, model #, serial #, and age or if it is eletronic pilot or a standing pilot(on all the time) this will help to solve this. Also, what stat you have.Try the things I mentioned, but please get back to me so we can solve you're problem. Thank you, and Sincerely,

Nov 21, 2009 | Heating & Cooling

1 Answer

Weil mclain heII-4 short cycles burner comes on for 30 seconds and then turns off and repeats

Make sure the exhaust fan is pushing out hot air and not obtstructed. Check the pilot assembly, clean ane make sure the sensor is well into the flame. Watch the flame to see if all burners are igniting. If not, clean the burners and the flame tray that spreads the flame to all of them. Look for a sensor at the farthest burner and make sure the probe is free of carbon and the wiring is tight.

Nov 08, 2009 | Heating & Cooling

1 Answer

I have a wall furnace whose fan short cycles on and off (even when the burner is still burning). I replaced the fan control switch, to no avail. Any Ideas?

Could the fan motor be heating up and shutting down on thermal overload? How long of a duration does it stay off before it starts again? Typically there is a bi-metal switch that rests on the heat exchanger and starts and stops the fan motor. If it is bad or not resting against the exchanger it will not operate as it should. Check the location of the switch. If it is touching but still cycling, test your switch with a multimeter set on Ohms. Let the heater run, jump the two wires you pulled off the switch (they are 120 volts so be careful) and watch your multimeter to see when the switch opens and closes. If it cycles as it has been, you have a bad motor. If the switch closes as the heat exchanger gets hot and stays hot as long as the heater is running, the switch is good.

Nov 06, 2009 | Heating & Cooling

1 Answer

Goodman furnace seems to be cycling too often. Burner not staying on long enough to put warm air into system. Burner quits after a few seconds then repeats.

dIf the burners are only staying on for about 5 seconds, you proably hav e a dirty flame sensor. Watch the burners light, the glow plug will light one end of the burners, in front of the last burner to light the will be a small thin rod, this rod must sense the flame or the gas will be shut down. Take a piece of steel wool and gently cleqan the rod.

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A 1979 Colman RV furnace. Blower shuts off shortly after burner shuts off leaving a hot heat exchanger. After 15 seconds blower comes on again blows for 10 seconds shuts off comes on in 15 seconds blows...

The fan limiting switch is acting up. It should stay running until lower temp is reached. It will cycle until the temp stays below or at the low setting. Limit switches are adjustable.

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