Question about Heating & Cooling

1 Answer

My furnace will not reach the desired house temperature in one cycle. It will run for several minutes, shut off, and repeat. It eventually reaches the desired temp but it take a long time and I feel it may be a symptom of a larger, looming problem. I have replaced the filter, and did a spot check on cold return ductwork to verify it is clean. I have also installed a new thermostat with no change. My next steps are to remove and inspect the blower, inspect and clean the flame sensor, and/or wire the blower to run faster. Any suggestions would be appreciated.

Posted by on


1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.

    Vice President:

    An expert whose answer got voted for 100 times.

  • Master
  • 468 Answers

There are a few different reasons for short cycling of a furnace.
1. Inadequate air flow. Not enough air moving through the furnace can cause it to overheat and trip the high temperature limit switch.
check to see that all registers are open and returns are not blocked.
2 Improper heat anticipator setting on thermostat. Some thermostats have a heat anticipator and too low of a setting can cause short cycling.

4 Partially blocked drain hoses. If the condensate backs up into the furnace it can shut the flame off and then when the condensate drains the furnace starts again. Check all drain hoses to make sure they are clear.
These are just some of the possible reasons for short cycling .
Hope this helps.

Posted on Dec 26, 2013

  • 1 more comment 
  • Lee Lee
    Lee Lee Dec 26, 2013

    Thank you for your response. My vents are open and clean, as are my return lines. I just performed an external check on my drains from the furnace. I could disassemble one and see the PVC was clean and I poured water down the other and it came out promptly on the discharge. Is this suffucient or do I need to open the furnace and check the drain lines on the inside? One drain line is off the condensate trap near the service panel and will be easy to access. The second is higher up, near the back, presumably from the heat exchanger area. Both are candidate problems? When you point me to the heat anticipator on the thermostat do you mean my wall thermostat or a thermostat inside the furnace. Thank you again and sorry for so many questions.

  • Lee Lee
    Lee Lee Dec 26, 2013

    I educated myself on the thermostat anticipator rate and know to what you refer. A few weeks ago, I replaced my thermostat in hopes a faulty thermostat was causing the cycling. That was not the solution. I have a Honeywell RTH2300B. It has a preset for heating cycle rate and I have it set according to the manual. It does not allow any further adjustment. The heating cycle rate I have selected is for a hot water or high efficiency furnace.

  • Lee Lee
    Lee Lee Dec 27, 2013

    I removed the panels and observed the furnace as it shut down. The flame burns for several minutes, a good blue flame. Eventually, the flame is lost. The unit begisn clicking, I assume an electronic ignition attempt is making the clicking sound. The hot surface igniter and/or flame sensor glows and (my memory is weak) I think there is a small blue flame at the igniter/sensor. It runs through the clicking process for five occasions before shutting down. The combustion air blowers stops and the circulating blower continues for about 30 seconds. I found a manual online with error codes. The code is 6 + 2 flashes. The manual says Soft Lockout: Indicates last failure was flame sense lost during run. Possible causes are: Flame sense rod contaminated or in incorrect position. Pilot burner located in incorrect position. Cycling, pressure switch Condensate drain blocked Pressure switches operation, tubing, and wiring. I am not sure what all of that means. I think my igniter and sensor are good as the furnace always comes on when demanded and always runs for several minutes. I do not know what the pressure switch portion is telling me. I suspect the drain issue is the problem. I hope that if I remove the hoses for the vent pipe drain and transition box drains, that I will see an obvious obstruction. I will also check the condensate trap, as both of the above drains flow through the trap. The trap does have CO2 warnings. If anyone has any ideas on the drains, I would be appreciative. Or, if you feel I am underestimating the likelihood of the igniter and sensor, I'd like to know that. Thank you for reading this long paragraph.



6 Suggested Answers

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

A 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
The service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Good luck!

Posted on Jan 02, 2017

  • 1420 Answers


There is a little switch on the circuit board. Look closely at the wiring diagram and it will indicate which switch to adjust. If not, review the operating manual for details.

Posted on Nov 25, 2008

  • 88 Answers

SOURCE: furnace blower not working how it should

first off buy yourself a honeywell stat, in my personal opinion lux stats are garbage, I have run into so many that are bad stats !!! but as far as your fan not shuting down, sounds to me like your fan center on your circuit board is bad and will not shut down the fan when needed, you will have to replace the circuit board, as the fan center is a part of the whole of the circuit board, hope that helps

Posted on Jan 20, 2009

  • 34 Answers

SOURCE: once temperature is reached the burner still trys

Need a thermocouple it sounds like to me.

Posted on Apr 17, 2009

  • 1420 Answers

SOURCE: Rheem RHQA Heater:Blower works but no heat.

Is there a setting on the thermostat for Auto or Fan? If so, make sure it is in the Auto setting. You will have a contactor that turns on the elements and a relay for the fan. Follow the wiring diagram to see which relay energizes the fan then unplug it to see if the fan stops.

Posted on Nov 03, 2009

  • 3249 Answers

SOURCE: XE 90 gas furnace--furnace will light and run for

hi check out the temp rise and fall on the fan control see if he has left the blower in the summer swich postion where it runs all the time

Posted on Feb 12, 2010

Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

I have a Honeywell programmable thermostat and I have central heat and air system. When I set the heat to a temperature above the inside temperature, the heater turns on for a short period of time and then...

I would say that the problem is in the furnace, not the thermostat. The Thermocouple or other temp sensor needs replacing, the sensor that tells the furnace that it is heating. It just keeps turning off and trying again in 3 minutes cycles.

Jan 01, 2015 | Heating & Cooling

1 Answer

I have a Braeburn 3200 and when the the temperature reaches the desired heat setting. The furnaces heat will shut off, but the fan will continue to run indefinetly. eventually blowing very cold air up

The fan relay is stuck in the on position. When the temperature drops the heater does not ignite because the fan is already running and ignition is locked out after the heat cycle starts an the fan turns on

Nov 16, 2014 | Heating & Cooling

1 Answer


Does the furnace stays off?.
Furnace are ment to cycle on and off because of limits .If you set to 70 furnace would cycle several times before reaching that temperature.
Just make sure your filters are clean and you got proper return air flow because lack of air flow will cause furnace to shut off sooner than normal

Jun 08, 2017 | Heating & Cooling

2 Answers

My goodman furnacs says my limit switch is bad blower works but does not ignite .....? its modle gmt070-3 and where is it located

There are several limit switches in the unit there in various places in burner compartment. One on blower housing . One thing that I would try is replaceing your filter and turn the power off to the furnace and try starting the system after power is D/C for 5 minutes.

May 02, 2011 | Goodman GMS90703BXA Heater

1 Answer

My goodman furnace model gms95 has gone ape. when the thermostate calls for heat, the furnace kicks on and starts to cycle but it wont stay on long enough to reach the set temp, before it kicks off. and it...

It sounds like your furnace is cycling off because your high temperature limit is tripping. This could be caused by a restriction of intake or outlet airflow. First thing to check is your intake air filter, clean or replace as needed. If that doesn't help, make sure your warm air registers are open, a rule of thumb is at least 60% of the total registers need to be open for adequate airflow. The high temp limits will reset themselves after they cool so that would explain it taking a few "cycles" to reach desired temperature. Good luck and please rate my answer if it was helpful.  

Jan 05, 2010 | Goodman Heating & Cooling

1 Answer

I have a comfort zone furnace. If it's 50 degrees in the house, and i set my thermostat to 70 or so,it takes at least 24 hours to reach 70 degrees. The furnace starts up and runs normally for about five...

When the thermostat calls for heat it should run until the room reaches the temperature setting then shut off. Is the blower motor running and can you feel air coming out of the vents? It sounds like the blower is either not running or putting out enough air to keep the furnace heating. The blower moves the heat from the heat exchanger to the room, if it can't remove enough heat from the heat exchanger there is a limit switch that will shut the burner off if it gets to hot and that's what it sounds like is happening.

Apr 25, 2009 | Heating & Cooling

2 Answers

Furnace blower not working how it should

first off buy yourself a honeywell stat, in my personal opinion lux stats are garbage, I have run into so many that are bad stats !!! but as far as your fan not shuting down, sounds to me like your fan center on your circuit board is bad and will not shut down the fan when needed, you will have to replace the circuit board, as the fan center is a part of the whole of the circuit board, hope that helps

Jan 19, 2009 | Coleman Propane Forced Air Heater...

Not finding what you are looking for?
Heating & Cooling Logo

Related Topics:

269 people viewed this question

Ask a Question

Usually answered in minutes!

Top Heating & Cooling Experts

Paul Carew

Level 3 Expert

3249 Answers

Dan Webster
Dan Webster

Level 3 Expert

8220 Answers

Tim Whalen

Level 3 Expert

3074 Answers

Are you a Heating and Cooling Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides