Question about Honeywell Electronic Programmable Heat/Cool Thermostat - CT3300A100 Heater

1 Answer

Furnace not cycling properly

My furnace is set at 72, but my house is kept at about 44. I put a new thermostat on but I am having the same problems. The furnace will start going through its normal cycles for about an hour or so and the temp will start to rise to around the mid 50's, never the same temp. Then it will just stop cycling and go back down to the mid to low 40's, again never the same temp. Sometimes the furnace will turn on, on its own. Other times I have to flip the switch located on the furnace off then on to get it to cycle. The temp never reaches freezing levels but won't warm up enough either. The igniter is electric is electric working fine. The vents all seem to be working and I changed the filter but the old one wasn't to bad. How do I get the furnace to run long enough to heat up my house? Is there a setting on my furnace I need to adjust?

Posted by on

  • 1 more comment 
  • dobsonj18 Jan 19, 2009

    All the grills are clear. I will try taking the filter out, thanks for the tip. Thwe furnace was installed in 2004. I just purchased the house 6 mths ago and I have never cleaned it, I will do so immediately. It doesn't look to bad but I will clean it anyway. The furnace is a Conquest 90, if that helps at all. Last night it ran for 3 1/2 hours without any problems. When I went to bed it quit working, I woke up cold! It is still running fine it just shutts off at random temps and won't turn back on without me manually doing so. Hopefully that helps you diagnose the problem. Let me know if there are any other questions I can answer to help you out with my problem. Thanks again for all your help.

  • dobsonj18 Jan 21, 2009

    I tried cleaning the flame sensor but it didn't work so I will replace it and see what happens. Thanks for the help, If you have any other suggestions that you think would help, that would be great.

  • Scott Magill May 11, 2010

    How old is the furnace? When was the last time it was cleaned? What does the back of blower motor like? Have you tried to take filter out? Have you checked the return grill in your house to make sure there is nothing in front of it blocking the air flow? Please give me some feed back and i can give you some other things to check.



1 Answer

  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert that got 5 achievements.


    An expert who has written 20 answers of more than 400 characters.

    New Friend:

    An expert that has 1 follower.

  • Expert
  • 70 Answers

Sounds like the flame sensor needs to be replace. You can try cleaning it with steel wool. This will get you by for a little while.

Posted on Jan 20, 2009

  • Scott Magill Jan 22, 2009

    where are the vents located on top of the house or out the side? Is there any snow on the ground? If there is the vent has a screen in it so birds don't get in their the vent could be getting plugedup. Before you reset the furnace next time you should have a sight galass you can see a red light see how many times it blinks should be like two or three blinks fast then a pause the the blinks again. this red light should be on the control board then on one of the front panels should tell you what the problem. the pressure switch could be causing the problem the control board should tell you if thats what it is



1 Suggested Answer

  • 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 Repairman 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 repair professionals here in the US.
click here to Talk to a Repairman (only for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


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



Related Questions:

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

How to reset the thermostat to shut off after 2 degrees/CT87B-4008?

on these thermostats remove the outer ring cover and in the lower right side you will see a slide adjustment. move it i believe left for closer cycles and right for longer cycles. it should be 2* on either side of set point. remember that the fan is not furnace shut off.and turning back and forth will not tell you anything. just set it and see how it works then change it again if you need to

Oct 13, 2014 | Honeywell CT87B ROUND 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 girlfriend has a forced air Goodman furnace in her house. Her furnace has been not running well. Whenever the filter gets dirty the furnace does not run right which it to be expected. The problem is...

where is the thermostat located? i should be on a inside wall in a comon room and not around lights, computer or heat vent or air return. a thermostat is just a switch and will operate in its enviroment. does the fan cycle off before the heat starts blowing again? the fan on these are on a timer that the t stat will have to "brake" open on reaching temp to shut off. not knowing where your at look this over and i hope it helps. i dont think i would let someone sell me a control board for this problem.

Feb 08, 2011 | Goodman GMS90703BXA Heater

1 Answer

Furnace starting

Hint number 1, get HVAC license. One mistake or misunderstanding and you could blow your house up.

Feb 21, 2009 | Heating & Cooling

4 Answers

Thermostat seems to be working, furnace does not always turn on

Joss sounds like the anticipator setting on thermostat i would replace it with a digital it will be more actturat . The furnace has to go over temp setting to turn off

Jan 15, 2009 | Honeywell Electronic Programmable...

1 Answer

Short cycling

There are a few reasons why your furnace is restarting after it reaches temp. and shuts off. First, if you have a mercury bulb thermostat it needs to be level and the heat anticipator needs set properly. If you have an electronic thermostat then you need to make sure the DIP switch settings inside are set properly for propane. If you have a digital thermostat there are also settings to be made for your type of heating. These settings will be explained in the thermostat installation instructions. Also, Make sure your furnace filter is clean. If this does not help then there are some other things to check which may need to be done by a technician depending on your mechanical aptitude. Hope this helps!

Dec 08, 2008 | Coleman Propane Forced Air Heater...

1 Answer

Fan on but no heat

I never liked the user un-friendliness of the Chromatherm, I would suggest finding a thermostat that you can understand and operate. Yes the Chromatherm is a good one, but so damned hard to figure out. Stay away from thermostats that still use mercury. Good Luck!

Oct 20, 2008 | Honeywell Heating & Cooling

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

828 people viewed this question

Ask a Question

Usually answered in minutes!

Top Honeywell Heating & Cooling Experts

Bill Long

Level 3 Expert

588 Answers

Paul Carew

Level 3 Expert

3087 Answers

vance jones

Level 2 Expert

120 Answers

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

Answer questions

Manuals & User Guides