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Carrier Furnace Not Turning On? 4 Common Causes (+ Fixes)

Turning on your Carrier furnace at the start of winter only to find that it’s not working is quite a disappointment. This problem can mean many things, so you should follow a step-by-step approach. 

Your Carrier furnace isn’t turning on because of problems with the thermostat, a tripped breaker switch, the fan is off, or the pilot light isn’t lit. Check the thermostat’s settings, ensure the furnace breaker switch and the fan are on, and reignite the pilot light to get your furnace to turn on.

We have compiled a list of common reasons why your Carrier furnace won’t turn on. We’ll help you fix the problem so that you and your family can stay warm. 

Problems With the Thermostat

The first part of the furnace you want to look at is the thermostat. A Carrier furnace not turning on is often a sign of a problem with the thermostat. Make sure the power to the furnace unit is turned on. Then take a closer look at the thermostat. 

There are a few issues that can affect a thermostat. This includes dead batteries, in which case the thermostat won’t send a signal to the furnace. When this happens, your furnace won’t start as it’s waiting for instructions from the thermostat. 

Some furnaces use a direct power connection instead of batteries. The problem may lie with the cables used to provide power to the device. If there are problems with the cables, the thermostat won’t be powered. 

How To Fix

First, check to ensure the thermostat is turned on and the set temperature is higher than the room temperature:

  • Thermostats that use batteries may simply need a new pair. Remove the thermostat from the wall and flip it over. You should see a battery compartment. Replace the batteries and put the thermostat back and test it.
  • If the thermostat uses a cable for power, switch off the furnace and remove the thermostat. Inspect the wires coming from the furnace. If you see a loose wire, reinstall it properly. If the C-wire is damaged, you need to have it replaced by an expert.

Here’s a video that explains how to replace the batteries in a thermostat:

Tripped Breaker Switch

There’s a breaker switch inside the power box of the furnace. The breaker switch is an essential safety feature that all Carrier furnaces have. 

When there’s a power surge, the breaker switch trips, blocking power to the furnace.

The primary goal of this is to prevent the power surge from damaging the furnace. When there’s a power spike, it can cause severe damage to any electric appliance.

How To Fix

To check if the breaker switch tripped, locate the power box. This part of the furnace is sometimes referred to as the fuse box. In addition to containing the breaker switch, it also houses a fuse.

Since you’re already checking the breaker switch, it’s a good idea to check the fuse too. Both act as separate safety mechanisms aiming to protect the furnace against a sudden spike of electricity:

  1. Turn off all power to the furnace. 
  2. Remove the screws that hold the panel on the front of the box in place. 
  3. Check the breaker switch. You can refer to the owner’s manual if you’re not sure where to look. If it tripped, flip it over to reset it. 
  4. While checking the breaker switch, take a look at the fuse too. Make sure the wire inside the fuse is still intact. If not, replace it with a fuse with the same rating. 

Watch this video if you need more help on replacing the furnace fuse:

The Fan Is Off

Another common yet overlooked problem is the fan. The fan switch has three settings — ON, OFF, and AUTO

The auto setting is what most people set it to. It allows the fan to switch on and off based on whether the furnace is running.

But if the fan is off, you might think that your Carrier furnace isn’t turning on as you’re not getting any heat inside your home.

How To Fix

This fix shouldn’t take too much time. Check the owner’s manual to see where the fan switch is located in your Carrier furnace. If it’s off, switch it to auto or on. 

It’s also possible that the wiring to the fan switch is faulty. If the switch is on, but the fan isn’t working, check the cables that connect the switch to the rest of the system.

Unlit Pilot Light

Another possible reason your Carrier furnace isn’t turning on is that the pilot light has gone out. This problem only applies to older furnaces that still use a pilot switch. You should first determine whether your furnace uses a pilot light or an electric ignitor by inspecting the furnace. 

But what does the pilot light have to do with the furnace not turning on?

You see, the pilot light is responsible for igniting the gas coming from the burners. It maintains a small flame at all times. 

How To Fix

There’s a simple fix for getting the pilot light to work again. You simply need to take a candle lighter and ignite it. You must see a flame on the pilot light before turning the furnace on.

Hint: Soot can build up on the pilot light over time. In this case, using a lighter will yield no flame. You must clean the pilot light to get it working again.

Open up the furnace, use fine sandpaper to clean the pilot light, and then ignite it. If it still isn’t working, ask an HVAC technician for help.

Summary

Your Carrier furnace probably isn’t turning on because of problems with the power supply. There could also be a fault with the pilot light or the thermostat. Go over each part mentioned in the article to find the problem.