Lennox Furnace Codes H70 – What You Need to Know

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Before you can troubleshoot your furnace, you need to know what is going on with your system. Several different codes and error messages could show up while using your furnace. Knowing what they mean and how to respond to them will make fixing the problem much easier. Learning more about the Lennox Furnace Codes H70 will help you diagnose issues before they get worse. If you have a Lennox gas furnace, there’s a good chance you also have a code that begins with H7 followed by another number. This is part of an extended set of codes that are used for all types of gas furnaces produced by Lennox. The extended codes are used because several different components send unique signals from their sensors or input points. In other words, even though all gas furnaces share some common codes and functions, there needs to be some way for each model to have its distinct code so technicians can easily identify the issue when diagnosing problems at a later time.

H70 Codes

H70 is the code that gets triggered when the gas valve detects a fault in the gas supply. This means that the gas valve is not able to complete the connection between the gas source and the furnace. It’s important to note that this does not necessarily mean that you don’t have any gas running to your furnace. It just means that the valve is not able to complete the connection between the two, either because of a blockage or a failed sensor. There are a couple of different reasons why the valve would not be able to connect the gas to the furnace. The first is if the furnace is connected to a faulty or damaged gas line. This could be due to corrosion, a leak, or a rodent chewing through the line. Another possible cause is that the gas shut-off valve for the gas line running to the furnace is not turned on. The valve could also be stuck shut or broken and unable to turn on fully.

H71 Code

If you get an H71 code, it means that your gas valve is not able to close the connection fully. This can be caused by several different issues, including a dirty or misaligned valve, a faulty sensor, or a broken valve seat. If the valve seat is broken, you may need to replace the valve. If the sensor is dirty or misaligned, you may be able to clean it or adjust it to make it work correctly again. If none of these issues apply to your furnace, you may need to replace the gas valve.

H73 Code

H73 is the code that will be triggered when your gas valve detects a short circuit. If this occurs, the valve will automatically shut itself off to protect the rest of your furnace. If you get this code, you will want to turn off the gas to your furnace right away and call a professional to come to check it out. Doing so can help prevent a fire from occurring.

H74 Code

H74 is the code that shows up when the gas valve detects an open circuit. In other words, it senses that the circuit is complete, but it is not sending any power through the circuit. This typically means that the wires coming from your furnace are either broken or disconnected. You should check your wiring to make sure that it is still connected properly. If the wires are connected and nothing looks broken, you may need to replace your gas valve.

H76 Code

H76 is triggered when the gas valve detects an overcurrent condition. This means that the current is running through the circuit at a level that is too high. This can be caused by a wire that is too small or a short in the wiring. If this code is showing up, you will want to make sure that the wiring is properly sized and that there are no shorts or other issues with the wiring. You may also want to replace your gas valve because this problem could be due to a defect.

H77 Code

H77 is the code that will show up when the gas valve detects a low voltage condition. This means that the voltage is too low and that the furnace is not getting enough power to run properly. The most common cause of this is a break in the power line that supplies power to your furnace. You will want to make sure that the break has been repaired before attempting to use your furnace again. This code can also be triggered if you have a circuit breaker turned on that is overloaded. You may even see two or three H7 codes triggered at the same time if multiple circuits are overloaded. If this is the case, you will want to turn off the circuit breakers that are overloaded to protect your furnace from being damaged.

Extended H7 Codes

While the H70-H77 are the most common Lennox furnace codes, you may occasionally see one that begins with H7 followed by another number. These extended codes are used by Lennox to account for all of the different sensors and inputs found on gas furnaces. For example, if the sensor that detects the pressure in the furnace’s run cap detects a fault, you will see a code beginning with H71. If a sensor detects that the motor is overheating, you will see an H71 code followed by a letter. These extended codes will vary depending on the model of furnace you have and the issues that are occurring. In most cases, you will only see an extended code when the furnace is shutting itself off. This can be an indication that the furnace is overheating, has a problem with a sensor, or is low on coolant. In any case, you should call a professional to come to inspect your furnace as soon as possible to make sure it does not need to be repaired or replaced.

Conclusion

Several different Lennox furnace codes can show up when using your furnace. Knowing what these codes mean and how to respond to them will make diagnosing and fixing issues much easier. The most common Lennox furnace codes begin with H70, followed by another number. You may also see an extended code that begins with H7 followed by another number from time to time.