Why Furnace Cycles Every 7 Minutes? How To Troubleshoot It?

You’ve moved to a new house and the furnace at home suddenly starts to turn on and off every 7 minutes. As this is the first time you’re facing this issue, you wonder if something is wrong with the system. Should you ask a professional to look at your furnace, or is this how it usually operates?

The furnace cycles every 7 minutes if it has a faulty pressure switch. It can also be due to the control board, the thermostat, or a corroded or dirty flame rod. For most of these issues, you’ll need to replace the faulty piece. You may need professional help.

In this article, I’ll cover various factors that can cause your furnace to cycle every 7 minutes. I’ll also suggest solutions for fixing this problem if you notice something wrong with the system.

1. The Pressure Switches Are Faulty

An easy way to identify which parts to inspect on your furnace is to look for blinking or flashing lights. Known as error codes, they are produced by LEDs. These error codes can vary depending on the furnace manufacturer.

If the lights point you toward the pressure switch, it doesn’t necessarily mean this part has a problem. In fact, it could be anything affecting this component’s functionality. 

How To Fix?

First, you need to identify what is causing the issue with the pressure switch. Is it malfunctioning or is it something else?

There are several reasons the Furnace switch can malfunction. For instance, your furnace will produce condensation during the cycle. Generally, this won’t be a problem as the exhaust pipe will remove the moisture and prevent it from building up inside the system.

However, if something is blocking the exhaust pipe, it can cause the condensate to stay inside the system and enter the inducer motor. This can happen if there is debris or an animal or a bird builds a nest on the exhaust pipe. As a result, the pressure switch will turn off.

Similarly, a blockage in the intake pipe can cause issues as this is connected to the pressure switch. For instance, heavy snowfall or plant debris obstructs airflow in the intake pipe. When this happens, the furnace cannot draw an adequate volume of air to start the combustion process. As a result, the system will keep cycling frequently instead of heating your house properly.

The exhaust pipe can also cause problems if it isn’t installed properly. Ideally, it needs to be going upwards with a tilt. If it goes in the opposite direction (i.e., downwards), condensate can build up in the pipe and enter the system.

Look at the intake and exhaust pipe and ensure nothing is blocking it. Also, make sure the exhaust pipes are angled upwards. You can provide support and lift the pipes every 4 ft–5 ft (1.22 m–1.52 m)

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If there’s nothing wrong with the intake and exhaust pipes, it could be the inducer motor. This component is responsible for improving airflow in the system, affecting efficiency. If the fans are damaged, they won’t work as expected. You’ll have to get a new one for the furnace, which is expensive.

If all these parts are okay, it could be the pressure switch itself. You’ll need tools like a multimeter and manometer for this test. With the multimeter, you should check the resistance value. The manometer can help test the water pressure and ensure the switch works properly.

You can also use an SDMN6 Dual-Port Manometer to test the pressure switch independently from the furnace. If the problem is with this part, you’ll need to replace it.

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Read: Why Furnace Keeps Running And No Heat?

2. The Control Board Isn’t Working Properly

The control board makes the blower motor, hot surface ignitor, and inducer motor work properly. It sends the correct voltage to these parts, ensuring they’ve enough power to run.

How To Fix?

The main reason why the control board doesn’t work properly is because of the wiring. Poor quality finish during manufacturing can cause this issue. It can also happen if a technician recently worked on the control board but wasn’t paying attention. Also, the vibrations from the furnace can make the wiring loose over time. 

The terminals, which are the ends of the wires, have to be soldered on the board properly. This ensures there’s proper contact. Otherwise, it increases the resistance, and the control board won’t send the correct voltage to various parts of the furnace. 

You can check the voltage readings with the help of a multimeter. As fixing this issue requires technical skills and knowledge about how the furnace works, it is always better to get a certified technician to take a look.

3. The Flame Rod Is Corroded or Dirty

The flame rod is essential to a furnace because it detects whether the system produces a flame. If it doesn’t sense one, it will turn off the furnace. The easiest way to check whether this component is faulty is to look at it after you turn on the furnace. 

If there is a flame and the system still turns off, the flame rod may be at fault. 

How To Fix?

If the problem is with the flame rod, the solution is simple. You need to clean this part, and it should work properly. You can use tools like sandpaper or steel wool. However, make sure you’re careful while using these tools.

The flame rod has a special coating, which helps it check whether the flame is active. You may remove this coating if you rub it too hard with sandpaper or steel wool. Then, the flame rod won’t work as intended.

If you’ve cleaned the flame rod several times, or it’s been years since you’ve replaced this part, I recommend installing a new one. 

Read: Why Furnace Blowing Cold Air? – Troubleshooting Guide

4. There’s Something Wrong With the Thermostat

The thermostat lets the furnace know how much to heat the house before switching to the resting cycle. If this component has an issue, it can explain why the system keeps turning on and off repeatedly. 

How To Fix?

There can be several reasons why the thermostat is causing issues with the furnace. For example, the heat anticipator isn’t set correctly, which is why the system is turning on and off rapidly.

You need to change the setting of the heat anticipator to fix this issue. Move the dial to a longer cycle and check whether it has fixed your problem.

Otherwise, the thermostat may not be working because it has old batteries. Swap out the batteries for new ones and test the furnace. 

If that doesn’t solve your problem, it can be the wiring. You’ll need to contact a certified technician to change the wiring.

Also, the thermostat can give you issues if it isn’t installed in the right place. The readings will be inaccurate if it is next to a heat source, like direct sunlight. For this issue, you’ll have to change the thermostat’s location. 

It is also possible that there are cracks in the heat exchanger, which can cause the furnace to short-cycle. I’ve written an article covering this topic extensively so you can quickly get to the bottom of this problem. 

Read: Cracked Heat Exchanger In Furnace – How To Troubleshoot?

Final Thoughts

If the furnace cycles every 7 minutes or is shorter than expected, you should check the pressure switches and every other component connected to it. The problem can also be due to the flame rod, which cannot detect a flame due to corrosion or dirt.

Lastly, the thermostat can also be responsible for the furnace to short cycle. I recommend getting a certified technician to look at the system, as they will quickly identify and fix the problem.

Related: High-Efficiency Furnace Venting Options