Why is Heating Still On When Thermostat is Off?

If you ever find your heating still on when thermostat is off, your thermostat is not always the problem.

As a matter of fact, this occurrence can be caused by multiple culprits, and that’s what we’ll be discussing in this guide!

Unlike other guides online, our tutorial will give you a complete walkthrough of the guide!

We’ll not only discuss what’s causing this, but we’ll also help you fix it by giving the complete steps to get rid of it!

If your heat continues to power on even when your thermostat is off, check the wiring of the thermostat. Check if there are wires touching each other or if there’s a shortage in the thermostat. Then, proceed to check if the gas valve is stuck open or if there’s a bad control board.

When you arrive at the situation where your heating system is still on when the thermostat is off, the first thing we need to do is to try and figure out what’s causing it to happen.

Common Reasons Why Heating Remains Even When Thermostat is Off

There are a few reasons why the heating of your HVAC system is maintained even if the thermostat has been turned off.

The most customary ones include, but are not limited to:

• Wire touching something it shouldn’t touch
• Shortage in the thermostat
• Bad/faulty/problematic control board
• Opened gas valve
• Malfunctioning furnace
• Broken thermostat

It’ll be difficult to pinpoint what the exact reason is for the heat to be on continuously even if the thermostat has been deactivated.

That is why, in this tutorial, we will give it to you in the most comprehensive ways we can!

Heating Still On When Thermostat is Off? – Fix Steps

Whether or not you have experience fixing these types of issues, you’ll find it easy to understand our guide!

Step #1: Check the Condition of the Thermostat

Before you go any further, you want to check and assess the condition of your thermostat first.

Doing this step initially will help you try to identify if it’s your thermostat causing the problem.

Here’s how you can check if your thermostat has a continuity problem:

1. Remove the faceplate of the thermostat.
2. Use a short, insulated jumper wire and short the R (power) and G (fan) terminals.

If the vents do not blow air, it means that the thermostat is good – it’s functioning normally.

On the contrary, if it blows air, it means that you’ve jumpstarted the thermostat; the problem is the faceplate, it’s not making contact with the wiring or sensors any longer.

Note: You can simply replace the faceplate of the thermostat by purchasing a new one because the problem is with the unit and it is irreversible.

Step #2: Double-Check the Wiring of the Thermostat

The next step is to double-check the thermostat’s internal wiring. These wires and cables are the device’s vessels in making power flow through it.

There are quite a few things that could signal the end of the wiring of the thermostat to the heater.

And these things include:

• Frayed wires
• Cut/sliced up wires
• Disconnected wires
• Burnt wires

What To Do If You Find These?

If you find loose or disconnected wires, simply screw them tightly and securely for a better connection.

However, if you see cut, frayed, or burnt wires, follow these steps:

1. Unscrew the terminal of the wire that’s damaged.
2. Then, using wire strippers, slice off the outer jacket.
3. This will expose a fresh section of the wire/conductor.
4. Finally, reattach it to the terminal and screw it back in place.

Shortage in the Wiring

In addition to these situations, there could also be shorting/shortage on the thermostat’s wiring.

This means that there are two (2) or more wires that are touching that shouldn’t be in contact with one another in the first place.

So, check if there’s a shortage in the wiring by following these simple and easy steps:

1. Remove the faceplate of the thermostat.
2. Unscrew the base or the back part of the thermostat to reveal the wires.
3. First, check if all the wires are in good condition.
4. Then, ensure that the wires are kept in place.

What you can do is to check the manual of your thermostat and have a look at how the wirings should be placed and installed.

Cross-check these positions to how your device’s wires are currently installed/positioned.

Step #3: Consider the Gas Valve

After that, the next thing you want to check is the burner’s gas valve.

The situation could be that the gas valve has been stuck open, which allows it to light the burner, even if the thermostat is turned off.

You can check this by going into the furnace cabinet and checking the valve that’s present. Usually, this valve will be connected to various wires and cables that run through the interior of the furnace.

1. Check if the gas valve is stuck open (if something’s blocking it).
2. Manually close the opening of the gas valve, but do not force it as it might snap.
3. Remove anything that could block its path of opening and closing on its own.

Many experts believe that this is a unique and rare situation; one that has a low possibility of happening. However, there’s still a possibility – it could still happen!

Step #4: Examine the Control Board

Last, but most definitely not least is to check the control board of your furnace.

Your board could be giving off the signal that your furnace needs to be hot even if you’ve set the thermostat to cool or if it’s turned off.

But how do you know if your control board is going bad?

Is the Control Bard of My Furnace Going Bad?

There are quite a few warning signs that can tell you whether your control board is going bad:

• Check the diagnostics and light indicators of the furnace
• Use a multimeter to check the power coming into your control board
• Test your transformer using a multimeter

If you find that your control board is already faulty, the next best step is to replace it. Here’s the process of how you can do it:

Replacing Your Control Board

Most people think that replacing the control board of the furnace is a job that needs to be done by an expert. But no, it’s actually doable.

In fact, here’s a summary of how the replacement is done:

1. Open the furnace’s control board.
2. Remove all the wires and cables connected to the board.
3. Unscrew the terminals using the necessary tool/screwdriver. 
4. After that, remove the blower motor wiring carefully.
5. Then, carefully pull the board out.
6. Once the old and faulty one is out, install the new board.
7. Place it inside the casing and reconnect all the wires to their respective places.
8. Install the wires of the blower motor last and

NOTE: In case you’re not familiar with wires and cables, take a picture of it before dismantling it. Ensure that the furnace is turned off before you start the process.

Once you’ve reattached all of them, the last step is to reassemble the furnace, turn it on, and test it.

When Should I Contact an HVAC Expert?

There would really be issues and situations where this process wouldn’t be enough.

So, should your heating still remain consistent during the time when the thermostat is turned off or deactivated, the next best step is to contact your local HVAC expert.

Let them know of the problem/dilemma you’re experiencing; give it to them in full detail and narrate what happened that led you to the situation you are in.

Moreover, inform them of the initial troubleshooting steps you’ve done. From there, they’ll be able to identify what the next best steps are to help you with your dilemma.

To fix the problem of your heating still being on even after the thermostat has been deactivated, check the condition of the thermostat. Then, ensure that there’s nothing wrong with the wiring. Check the gas valve and see if it’s been stuck open, and finally, assess the control board of your furnace.

Read Next: Does Low Battery Affect Thermostat?

Bottom Line

With this guide, the dilemma of your heating still on when the thermostat is off should bid you farewell!

Guides and tutorials as comprehensive as this will never leave you bothered and stressed!

Now, you know that even if you’re a beginner in this field, you’ll be able to do it!