What to Do If Your Thermostat Was Just Replaced & Now Your HVAC System Won’t Turn On

When you change out your thermostat, it should make keeping your home comfortable more convenient. It shouldn’t leave you wondering why your HVAC system isn’t kicking on.

If you just replaced your thermostat and nothing is happening, don’t panic!

Watch our video and read on for a few simple things you can check on your own before giving our Wheat Ridge HVAC or Arvada HVAC techs at Mighty Pine a call!

Step 1: Check Power and Connections

Sometimes the problem isn’t the thermostat at all but just a power problem feeding your system. 

• Breaker panel: Head to your breaker box and confirm that the HVAC breaker hasn’t tripped. If it has, reset it and see if your system will start back up.
• Furnace and air handler switch: Look for the switch near your furnace or air handler, which often looks like a regular light switch. Check that it’s flipped to the ON position.
• Thermostat wiring: Double-check that each wire is connected to the correct terminal on your thermostat, which are commonly R, C, W, Y, and G. Even one loose or misplaced wire can stop your system from running altogether.

If you are experiencing frequent circuit breaker tripping or wiring trouble, you need help from a licensed electrician to make sure your home is safe. Our team at Mighty Pine can come out to look at your wiring and electrical panel to make sure your circuits are up-to-date and your electrical panel can handle the demand of your household. We can also discuss how to keep your home safer with surge protectors or new switches and outlets.

Step 2: Confirm Thermostat Power

Once you’ve looked over different power sources for your system, it’s time to see if the thermostat itself needs an intervention.

• Batteries: Try swapping out the batteries if you have a battery-powered thermostat. 
• C-wire connection: Many smart thermostats need a C-wire for constant power. If it isn’t connected or wasn’t used with your old thermostat, the new one may not turn on.

Step 3: Look Over System Safety Checks

Did you know that modern HVAC systems have built-in safety features that will shut them off under certain conditions?

• Door safety switch: If your furnace or air handler access door isn’t closed securely, the safety switch won’t allow your system to run.
• Drain or float switch: Some systems have a switch that shuts everything off if the condensate drain is clogged. On the upside, it prevents water damage to your home.

When It’s Time to Call a Pro

If you’ve gone through our checklist and your HVAC system still isn’t turning on, you probably have a deeper problem going on in your system. Some of the possible culprits include:

• A blown low-voltage fuse on the furnace board
• Wiring issues between the thermostat and the HVAC system
• An incompatible thermostat

Don’t try to take a DIY approach. You could void your HVAC or thermostat warranty, expose yourself to risk, or create an electrical hazard. Instead, call one of our HVAC experts at Mighty Pine to diagnose the problem and fix it safely and thoroughly.

Call Mighty Pine for HVAC and thermostat assistance today.

Keep your home comfortable and safe year-round with HVAC and electrical help. Our team offers the services you need, from heating and cooling maintenance to repairs, installations, electrical panel upgrades, and more.

Give us a call today and we’ll get your thermostat working again!

Call (720) 538-8755