Carrier Furnace Ignition Lockout – What to Do?

Carrier Furnace Ignition Lockout – What to Do?

[vc_row][vc_column][vc_column_text]A furnace that stops heating can be disastrous, especially if the weather outside your home is extremely cold when the carrier furnace enters lockdown mode. Do you know how to deal with this issue properly? We’ve combed the internet for answers to your questions.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”7178″ img_size=”full” alignment=”center” onclick=”custom_link” link=”″][vc_custom_heading text=”everydrop by Whirlpool Ice and Water Refrigerator Filter 1″ font_container=”tag:h3|font_size:17|text_align:center” use_theme_fonts=”yes” link=”″][/vc_column][vc_column width=”1/2″][vc_single_image image=”7179″ img_size=”full” alignment=”center” onclick=”custom_link” link=””][vc_custom_heading text=”MervFilters 20x20x1 MERV 8 Air Filter, 6 Pack” font_container=”tag:h3|font_size:17|text_align:center” use_theme_fonts=”yes” link=””][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]If your Carrier furnace has an ignition lockout, you should inspect some of its components. Examine them thoroughly to see if they need to be cleaned or replaced. These common carrier furnace parts may need to be serviced to resolve this issue.

  • Ignitor
  • An air filter
  • Fan
  • The limit switch.
  • Flame detector.

Isn’t it simple? So, read on because there’s a lot of information below. We’ll go over the various types of ignition lockouts and their causes. Follow us down below!

Also check: American Standard AC Red Light Blinking – Why And What To Do?

What Does Ignition Lockout in Your Furnace Mean?

Ignition locks are classified into two types: soft locks and hard locks. Soft and hard lockouts can occur in furnaces. The purpose of these ignition lockouts is to cut off all power to the furnace unit.

Carrier furnaces now use special sensors in their systems to detect abnormal conditions. Each sensor sends a signal to the furnace console to detect a problem or dangerous situation. Locking down furnace controls eliminates any potential dangers. The furnace will not change ignition lockout modes until it has been reset, regardless of the cause.

When Does A Furnace Enter Soft Or Hard Lockout Mode?

You will encounter ignition blocks during the overall maintenance of the furnace system. You can avoid these problems if you understand why they occur. Even if the furnace is in a “soft lock” state, you can still attempt to restart it. In contrast, if the furnace fails to start four times a row, it will be turned off “tough lock.”

This means that the furnace system will render it inoperable in three hours. This usually indicates faulty wiring or a faulty gas valve relay.

What Causes Ignition Lock in a Carrier Furnace?

Failing to ignite the burner causes a furnace to enter the ignition lockout. This is due to a few flaws. However, most of them are products that do not provide regular service.

Here are some of the most common causes of misfires and how to deal with them.

Flame Sensor Failure:

A faulty flame sensor is one of the most common causes of an ignition lockout. Its purpose is to detect the presence of a flame before turning on your furnace igniter. If the sensor is damaged, it will be unable to detect the flame.

The system will then stop the ignition process and completely lock the system to protect it from further damage. Check the status of the flame sensor to avoid this issue.

Faulty Ignition System:

A faulty igniter is another common cause of carrier furnace ignition lockout. The flame sensor will not turn on if the furnace igniter does not ignite within a few seconds. This can also happen if the pilot is on. The faulty igniter should be replaced as soon as possible.

The Limit Switch Is Not Responding:

Limit switches on the furnace unit monitor air pressure and heat transfer temperature.

A limit switch will cut off the gas supply line if the temperature or pressure is too high or too low. If this unit fails, it will be unable to properly regulate pressure and temperature, so replacing it will resolve the issue.

What Would Trip A Limit Switch And Cause The Ignition Lockout?

Broken or defective heating system components frequently cause misfires. However, other factors concerning this issue must be addressed to avoid it completely.

Clogged Air Filter:

Another cause of an ignition lockout is a dirty air filter in the furnace unit. As previously stated, limit switches require adequate airflow to function properly with your furnace.

Operating the furnace unit with a clogged filter will reduce ideal airflow, trip the limit switch, and eventually lock up the system. Every 30-60 days, you should replace dirty HVAC filters in your home.

A Leaking Air Duct:

Limit switches ensure that the furnace system receives adequate air pressure and heat flow. This problem is solved by sealing the duct, which increases the system’s efficiency by about 20%.

How Do You Tell If Your Limit Switch Is Faulty?

Determining whether the furnace unit’s limit switches are defective is critical for the furnace’s efficient operation. Limit switches monitor the system’s gas pressure and temperature output.

A digital multimeter connected to the limit switch can accurately evaluate and determine if there is a failure. The typical operating voltage of the limit switch is less than 0.1 volts DC VDC.

The limit switch may be defective if the voltage drop reading is 0.2 VDC or higher. Limit switch contacts can rust, wear out, or break over time.

Also check: Dyson Fan Has A Burning Smell – Why And What To Do?

How To Reset A Carrier Furnace

A simple reset can easily resolve a carrier furnace unit ignition interlock failure. Trying to repair the furnace before consulting an HVAC technician is not a bad idea.

Of course, DIY repairs are acceptable if you can complete the necessary steps in your specific situation. We’ve outlined a few simple steps for resetting your carrier furnace below.

  1. Check that your thermostat is turned off. This ensures safety if it is accidentally turned “on” while resetting the furnace.
  2. Turn off the circuit breaker for the furnace unit or unplug the power cord from the electrical outlet.
  3. Leave everything to the system or reboot for 30 seconds.
  4. Flip the circuit breaker back to the “on” position.
  5. Finally, you can change the thermostat to “on.”


One or more faulty components are associated with the carrier furnace ignition interlock. Critical parts must be serviced regularly to keep your furnace system in good working order.

Learn about all of our useful information to assist you in properly maintaining your carrier furnace unit. We can now confidently depart, leaving you with all of this vital information.[/vc_column_text][/vc_column][/vc_row]


About Author

Mobeen Shahid

Mobeen Shahid

Mobeen Shahid is a Mechanical Engineer with two years of experience in the HVAC industry. His passion is analyzing HVAC issues, and he works relentlessly to devise customized solutions. He has been in the industry long enough to know the ins and outs and ensures that areas are optimally heated, cooled, and ventilated.

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