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New Thermostat Problem or Gas Furnace IssueNew Thermostat Problem or Gas Furnace Issue - Richard, I have a natural gas thermostat I just replaced this with a new Honeywell thermostat. It was working fine but in the last couple of days, I have to switch it to off then on to get the unit to run and blow heat. It never reaches temp then I have to repeat the process. Please help as this thermostat is new I can’t think that it’s the problem. Is it a problem with the new thermostat or a problem with the gas furnace? Thanks for your help!!

New Thermostat Problem or Gas Furnace Issue

First, let’s review what happened and then ask a few questions. Hopefully, we can zero in on the problem and get it working correctly. With modern thermostats, it is difficult to make the wrong thermostat selection. In the old days, not too long ago, thermostat selection was critical. Manufacturers made thermostats for a specific HVAC application. That made it necessary for the customer to get the correct thermostat for the HVAC system they have. In modern times, manufacturers make most of their thermostat for one product will fit all. Although, depending on your HVAC system, it will depend, in some cases, on the type of thermostat selection. For your case, I think it is pretty straight forward and doubt you made an incorrect selection.

Questions and Answers

So you installed a new thermostat, and everything worked correctly for a few weeks? Then after a few weeks, the system starts operating erratically? The real question is: Is it something wrong with the new thermostat installation or is it a problem with gas furnace? To remove any doubt, I would do the following:

  • First, go back and check the wiring to make sure everything is tight. No loose wires with the thermostat installation. This is basic thermostat troubleshooting procedures.
  • Make sure all the thermostat wiring colors are correct and terminated properly. Also, make sure none of the wires are touching at the tips.
  • Next, if this is a digital thermostat, I would go through all the settings. That will include checking the setback settings and the installation parameters. A thorough check of ALL the settings in the thermostat is necessary to make sure all is proper.
  • Next, I would go to the furnace and unhook the red wire and the white wire from the control board. Then, on the control board, with the thermostat wires completely isolated, I would jumper between white and red. White and red on the furnace, not the thermostat. It is important to make sure thermostat wires are disconnected in this procedure. Not doing so will cause problems with the thermostat. Problems that could result in destroying it. Disconnect the wires before jumping out the system.

New Thermostat Problem or Gas Furnace Issue

Jumping between red and white on the gas furnace control board will cause the system to go into heating mode. The system should offer normal operating service. Doing this procedure will let you know if the problem is with the gas furnace or the thermostat. If the gas furnace makes the same behavior that you mentioned above then your problem is with the gas furnace. You need to call an HVAC service company to come and troubleshoot the problem and repair it. The only issue with doing it this way is if the problem is intermittent. It’s the same as taking your car to a mechanic when it is making a funny noise.

As soon as you drive into the garage the car stops making the unusual noise. Intermittent problems in HVAC systems can be just as frustrating not only for you but also your HVAC service company.

Experience Pays

This is why it is very important when calling an HVAC service company, that you get someone with experience. It is very possible an experienced technician has observed this problem before. As an HVAC technician, I can talk to someone on the phone and have them describe the problem to me. In most cases, I can identify the problem immediately. Furthermore, I used to play a game with my apprentices to help them think about the problem before we arrived at the service call. I would look at the trouble ticket and sometimes talk to the customer.

I would have a basic description of the problem. Furthermore, I would quiz the apprentice when we were on our way to the service call. It would sharpen their skills and make them think about things to look for when we arrive. Lastly, it also told me a lot about the apprentice and how they applied themselves and the knowledge they learned.

Conclusion | New Thermostat Problem or Gas Furnace Issue

So recapping the issue, make sure to double-check everything with the thermostat. That includes the wiring and the settings inside the thermostat program. If that all checks out, jump out the wires in the furnace. If the problem replicates itself when you do that, then the problem is with the gas furnace. In that case, you need to call a service company to repair it. If the problem is intermittent, you may call a company anyhow to get the problem correct right away. It never hurts to have someone go over the system anyhow. I know we didn’t exactly solve your problem, but we did give you many areas to look at for a solution to the problem.

You may end up calling in a service company to repair it. Again, if you do, then try to get a competent technician with lots of experience. I know many companies offer their techs extra training, and this helps sharpen skills. HVAC is far and wide technical field requiring skills in many areas of physics. Some of the best training I ever received was from manufacturers. Although the experience is the best training one could ever get. I wish you luck and hope this helps you solve the problem.

High Performance HVAC Heating & cooling

New Thermostat Problem or Gas Furnace Issue


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