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Fixing a Post-Installation Furnace: 6 Tips to Start


Having just installed a new furnace system, it can be frustrating when the HVAC pro fails to start up due to issues like an intermittent pilot igniter, clogged filter, or dirty flame sensor. However, furnace problems are a common issue that many homeowners face in their house. When faced with furnace problems, it is important to seek professional furnace repair services from an HVAC pro. It is crucial to address common furnace startup problems promptly to ensure efficient gas furnace repair. This guide will provide an overview of troubleshooting steps for non-starting furnaces and help you diagnose and fix problems related to the heating system, heating element, flame sensor, and blower.

After installation, some common issues may prevent your heating system from starting. If you’re experiencing this problem, it’s best to call an HVAC pro to inspect the burners and flame sensor. These common furnace problems could range from issues with the front panel to more complex internal malfunctions, such as furnace blower noises. It’s important to address these issues promptly to avoid the need for costly furnace repair. By following the troubleshooting steps outlined in this guide, you can identify and resolve furnace blower, burners, sensor, and home problems without having to call an HVAC technician immediately.

Stay tuned as we explore the most common causes of startup problems with home furnaces, including issues with burners and blowers. This step-by-step guide will equip you with the knowledge needed to get your furnace up and running again.

Possible Reasons for a Furnace Not Turning On

Lack of power supply to the furnace

One common reason why a furnace may not turn on after installation is due to a lack of power supply. This can happen if the blower and burners do not receive the power they need. To troubleshoot this issue, follow these steps. If the furnace does not receive electricity, it will not be able to start up and provide heat. In this case, you may need to check the blower to ensure it is functioning properly. This is an important step in troubleshooting the issue. This can happen if there’s a problem with the circuit breaker or fuse that controls the furnace’s power blower. In this case, you will need to take the following step to fix the issue. To troubleshoot furnace problems, the first step is to check if the circuit breaker hasn’t tripped or if the fuse hasn’t blown. Additionally, it’s important to inspect the blower for any issues.

Malfunctioning thermostat causing startup failure

Another possible culprit behind a furnace failing to start is a malfunctioning thermostat step. It could be that the blower is not functioning properly. The thermostat acts as the control center for your heating system, telling the blower when to turn on and off based on temperature settings. It is an essential step in maintaining a comfortable indoor environment. If the thermostat isn’t working correctly, it may not send the signal to start up the furnace. This step is crucial for proper furnace operation. To troubleshoot this issue, follow these steps: try adjusting the temperature settings or replacing the batteries in your thermostat.

Clogged air filters restricting airflow and preventing ignition

Clogged air filters can also lead to startup failure in furnaces, making it an important step to regularly check and replace them. Air filters are the first step in trapping dust, debris, and other particles from circulating through your HVAC system. However, over time, these filters can become dirty and clogged, limiting airflow and affecting ignition step. When airflow is restricted, it puts strain on your furnace’s blower motor and heating elements, making it difficult for them to function properly. This can be resolved by following a simple step. Regularly changing or cleaning air filters is an important step that can help prevent this issue.

Faulty wiring or loose connections disrupting furnace operation

Faulty wiring or loose connections can cause disruptions in the operation of your furnace. In order to fix this issue, it is important to follow a step-by-step process. If there are damaged wires or loose connections between components like the blower motor or heating element, it can prevent proper functioning of the furnace. This can be resolved by following a step to check for any damaged wires or loose connections. In such cases, the first step is to seek professional assistance to inspect and repair any faulty wiring issues.

When troubleshooting a furnace that won’t start post-installation:

  • Check the power supply and ensure that the circuit breaker hasn’t tripped or fuse hasn’t blown. Make sure to follow this step.

  • Verify if the thermostat is functioning correctly by adjusting temperature settings or replacing batteries.

  • Regularly clean or replace air filters to prevent clogging and restricted airflow.

  • If there are any signs of faulty wiring or loose connections, seek professional help for inspection and repair.

Remember, safety should always be a priority when dealing with furnaces. If you’re unsure about any troubleshooting steps, it’s best to consult a qualified HVAC technician to avoid any potential hazards.

Safety Measures: Understanding the Safety Switch on Furnace Door and the Safety Float Switch

It’s crucial to understand the safety measures in place. Two essential safety devices to be aware of are the safety switch on the furnace door and the safety float switch.

Role of Safety Switch in Preventing Accidents during Maintenance or Repairs

The safety switch on the furnace door plays a vital role in ensuring your safety while working on your furnace. This device acts as a safeguard by shutting off power to the furnace when you open the door. It prevents accidents such as electric shocks or injuries caused by moving parts inside the unit.

Here are some key points to consider about the safety switch:

  • The safety switch is typically located near the top or side of your furnace’s access panel.

  • When you open the furnace door, this switch interrupts power supply to prevent any mishaps.

  • It works similarly to how a light switch turns off power when flipped.

It’s important always to keep this safety feature in mind when performing maintenance or repairs on your furnace. Make sure you turn off power before opening the door by switching off both electrical and gas supplies. This will help protect you from potential hazards.

Functionality of Safety Float Switch in Detecting Water Leaks and Shutting Down Furnace

Another critical safety device is the safety float switch, which helps detect water leaks within your HVAC system. This device is usually installed in areas where water can accumulate, such as drain pans or condensate lines. Its primary function is to shut down your furnace if it detects excessive water levels, preventing damage caused by flooding.

Here are some key points about how a safety float switch works:

  • The float switch contains a small plastic float that rises with increasing water levels.

  • When water reaches a certain level, it triggers an electrical circuit connected to your furnace.

  • This circuit shuts down the furnace to prevent further water damage.

Ensuring proper installation and functionality of the safety float switch is crucial. Regularly inspecting and cleaning drain pans, condensate lines, and the float switch itself can help prevent clogs or malfunctions that may lead to water leaks.

By understanding the role of these safety devices in your furnace, you can take necessary precautions to avoid accidents and protect your HVAC system from potential damage. Remember to always follow manufacturer guidelines for maintenance and repair tasks.

Checking Ignition Components: Ignition Switch, Ignition Sensor, and Electric Ignition/Pilot Control

To troubleshoot a furnace that won’t start post-installation, it’s essential to examine the ignition components. These components play a crucial role in initiating the heating process and ensuring the presence of a flame. Let’s delve into the purpose of the ignition switch, the function of the ignition sensor, and how to troubleshoot different types of ignition systems.

Purpose of Ignition Switch

The ignition switch is responsible for starting the entire heating process in a furnace. When you adjust your thermostat to increase or decrease the temperature, it sends an electrical signal to activate the ignition switch. This switch then allows electricity to flow through to other components such as the motor and igniter.

Role of Ignition Sensor

The ignition sensor is an important safety feature that detects whether there is a flame present in your furnace. It ensures that fuel is only released when there is an actual flame, preventing any potential hazards caused by gas buildup without combustion. If there is no flame detected by the sensor, it will shut off the gas supply to avoid any dangerous situations.

Different Types of Ignition Systems

There are two common types of ignition systems used in furnaces: electric ignition and pilot control (also known as intermittent pilot igniter). Each system has its own troubleshooting methods:

  1. Electric Ignition:

  • Check for power supply: Ensure that your furnace has electricity running to it by checking if circuit breakers are tripped or if there’s a blown fuse.

  • Inspect wiring connections: Look for loose or damaged wires that may be preventing proper electrical flow.

  • Examine control board: The control board could be faulty or damaged; consider consulting a professional technician for further inspection.

  1. Pilot Control (Intermittent Pilot Igniter):

  • Verify pilot light status: Check if your pilot light is lit. If not, follow the manufacturer’s instructions to relight it.

  • Clean the pilot assembly: Over time, the pilot assembly can accumulate dirt or debris, which may hinder proper ignition. Use a soft brush to clean it gently.

  • Check for gas supply issues: Ensure there is an adequate supply of gas reaching the pilot assembly. If not, contact your gas provider for assistance.

Remember to consult your furnace’s manual for specific troubleshooting steps tailored to your model and brand.

By addressing issues with the ignition switch, ignition sensor, and electric ignition/pilot control systems, you can effectively troubleshoot a furnace that won’t start post-installation. Always prioritize safety when dealing with any components involving electricity or gas.

Gas Line and Thermostat Check: Common Issues Affecting Furnace Startup

When troubleshooting a furnace that won’t start after installation, it’s crucial to evaluate both the gas line and thermostat. These components play a significant role in ensuring proper furnace operation. Let’s delve into some common issues that may arise with the gas line and thermostat, causing startup failure.

Potential gas line problems causing startup failure

One of the first things to check when your furnace won’t start is the gas line. Several issues can arise with the gas supply, leading to startup failure. Here are some potential problems to consider:

  1. Gas valve issues: Ensure that the gas supply valves leading to the furnace are fully open. Sometimes, they may get accidentally closed during installation or maintenance.

  2. Insufficient gas pressure: Low gas pressure can prevent the furnace from starting up properly. Check if there are any restrictions or blockages in the gas line that could be affecting the flow of natural gas.

  3. Pilot light malfunction: If you have an older furnace model with a pilot light, make sure it is lit correctly. A faulty pilot light can prevent ignition and cause startup failure.

  4. Gas leak: Gas leaks are hazardous and must be addressed immediately by a certified furnace services technician in Portland. If you suspect a gas leak, shut off the main gas supply and contact your utility company right away.

Importance of checking thermostat-related issues affecting furnace operation

The thermostat plays a crucial role in communicating with your furnace and regulating its operation based on temperature settings. Here are some thermostat-related issues that may affect furnace startup:

  1. Incorrect thermostat settings: Double-check that your programmable thermostat is set to “heat” mode at an appropriate temperature for your heating and ac service comfort needs.

  2. Faulty wiring or connections: Inspect the wiring connections between your thermostat and furnace for any loose or damaged wires that could disrupt communication signals.

  3. Malfunctioning thermostat: If your thermostat is not functioning correctly, it may not send the proper signals to the furnace, causing startup failure. Consider replacing it if necessary.

  4. Heat exchanger or air filter issues: A dirty air filter or a malfunctioning heat exchanger can impact airflow and prevent the furnace from starting up. Regularly clean or replace the air filter and have a professional inspect the heat exchanger for any problems.

Remember, troubleshooting a furnace that won’t start after installation requires careful evaluation of both the gas line and thermostat. By addressing potential gas line problems such as gas valve issues, low pressure, pilot light malfunction, and gas leaks, you can ensure proper fuel supply to your furnace. Checking for thermostat-related issues like incorrect settings, faulty wiring or connections, malfunctioning thermostats, and airflow obstructions will help identify any problems affecting communication between your thermostat and furnace.

Circuit Breakers: Tripped Breakers and their Impact on Furnace Operation

If you’ve recently installed a furnace and it’s not starting up, one possible culprit could be a tripped circuit breaker. Circuit breakers are designed to protect electrical circuits from overloading or short circuits by automatically cutting off the power supply. When a circuit breaker trips, it interrupts the flow of electricity to the furnace, causing startup failure. Here are some signs that indicate a tripped breaker might be the cause:

Signs of a Tripped Breaker

  1. No Power: If your furnace is completely unresponsive and shows no signs of power, such as lights on the control panel or sounds indicating ignition attempts, it’s likely that a tripped breaker is to blame.

  2. Partial Functionality: In some cases, certain components of the furnace may still work while others do not. For example, you may have power to the blower fan but no heat being produced in your heating and ac service. This partial functionality can be indicative of a tripped breaker affecting specific circuits.

Resetting Circuit Breakers Safely

To troubleshoot this issue and potentially resolve it without professional help, you can try resetting the circuit breakers safely by following these steps:

  1. Identify the Correct Breaker: Locate your home’s main electrical panel or fuse box and find the corresponding circuit breaker for your furnace. It should be labeled accordingly.

  2. Switch Off: Flip the switch for that particular circuit breaker into its “off” position.

  3. Wait for a Moment: Give it a few seconds before proceeding to ensure any residual charge dissipates.

  4. Switch On: After waiting, flip the switch back into its “on” position firmly until you hear or feel it click.

It’s important to note that if resetting the circuit breaker doesn’t solve the problem or if it continues to trip repeatedly, there may be an underlying electrical issue that requires professional assistance. In such cases, it’s best to contact a licensed electrician or HVAC technician to diagnose and resolve the problem.

Pros and Cons of Resetting Circuit Breakers


  • Simple Troubleshooting: Resetting a tripped circuit breaker is a relatively simple troubleshooting step that can potentially solve the startup issue.

  • Cost Savings: If the problem is indeed a tripped breaker, you can save money by resolving it yourself instead of hiring a professional.


  • Safety Concerns: Working with electricity always carries some level of risk. If you’re not comfortable or experienced in handling electrical components, it’s best to leave it to the professionals.

  • Underlying Issues: A tripped breaker could be indicative of an underlying electrical issue that needs professional attention. Resetting the breaker may only provide a temporary solution.

Investigating Limit Switch Functionality for Furnace Startup

The limit switch plays a crucial role in regulating the temperature inside your furnace. It acts as a safety device that monitors the heat levels and prevents any potential hazards. However, there are instances where issues with the limit switch can cause shutdowns or prevent the furnace from starting up altogether.

Purpose of Limit Switch in Regulating Temperature Inside the Furnace

The main purpose of a limit switch is to ensure that the temperature inside the furnace remains within safe limits. It is designed to monitor and regulate both high and low temperatures. When the temperature rises above a certain threshold, known as the high limit, it triggers a shutdown to prevent overheating and potential damage to components or even fire hazards.

Conversely, if the temperature falls below a specific threshold, referred to as the low limit, it activates mechanisms to restore heat production until optimal conditions are reached again. By constantly monitoring these temperature levels, the limit switch helps maintain safe operating conditions for your furnace.

Issues with Limit Switch Causing Shutdowns or Preventing Startup

There are various issues that can arise with the limit switch, leading to shutdowns or preventing startup:

  1. Faulty High Limit Switch: If your high limit switch malfunctions or becomes faulty, it may trigger unnecessary shutdowns even when there is no actual danger of overheating. This can be frustrating and disrupt proper furnace operation.

  2. Pressure Switch Problems: The pressure switch works in conjunction with the limit switch to ensure proper airflow within your furnace system. If there are any issues with the pressure switch such as clogs or malfunctions, it can interfere with startup procedures.

  3. Power Supply Issues: A malfunctioning power switch or capacitor can also impact how your furnace’s limit switch functions. If there is a problem with the power supply, it may prevent the limit switch from receiving the necessary signals to initiate startup.

Testing and Troubleshooting Limit Switch Problems

If you suspect that your furnace’s limit switch is causing shutdowns or preventing startup, here are some steps you can take to test and troubleshoot the issue:

  1. Inspect for Visible Damage: Start by visually inspecting the limit switch for any signs of damage or wear. Look for loose connections, frayed wires, or any other visible issues that could be affecting its functionality.

  2. Check Continuity: Use a multimeter to check for continuity in the limit switch. This will help determine if it is functioning properly or if there is a break in the circuit.

  3. Clean and Reset: Sometimes, dust or debris can accumulate on the limit switch, affecting its performance. Carefully clean the switch using compressed air or a soft brush. Try resetting the switch by turning off power to your furnace for a few minutes before turning it back on.

  4. Seek Professional Assistance: If you have gone through these troubleshooting steps and are still experiencing issues with your furnace’s limit switch, it may be time to seek professional assistance from an HVAC technician who can diagnose and resolve more complex problems.

Remember, when dealing with furnace troubleshooting and repairs, always prioritize safety first. If at any point you feel uncomfortable or unsure about performing any of these steps yourself, it is best to consult with a qualified professional who can ensure proper resolution without jeopardizing your safety or causing further damage to your furnace.

Troubleshooting Tips: DIY Steps to Try When Your Furnace Won’t Turn On

Simple Steps to Check Power Supply, Thermostat Settings, and Air Filters

If you’ve recently installed a new furnace and it’s not starting up, don’t panic! There are some simple troubleshooting steps you can take to try and get it running. First things first, check the power supply. Make sure the furnace is properly plugged in and that the circuit breaker hasn’t tripped. If everything seems fine on that front, move on to checking the thermostat settings. Ensure that it’s set to heat mode and at a temperature higher than the current room temperature.

Next up is checking the air filters. A clogged or dirty filter can restrict airflow and cause your furnace to malfunction. Take out the filter and give it a good look – if it’s covered in dust or debris, it’s time for a replacement. Remember, clean filters help your furnace run more efficiently!

How to Inspect Ignition Components for Signs of Malfunction

If your power supply, thermostat settings, and air filters all seem fine but your furnace still won’t start, it might be an issue with the ignition components. Start by inspecting the pilot light (if applicable). Is it lit? If not, follow the manufacturer’s instructions on how to relight it safely.

For furnaces with electronic ignition systems, check for any error codes displayed on the control panel. These codes can provide valuable information about what might be causing the startup issue.

Take a look at other ignition components like spark igniters or hot surface igniters. Are they worn out or damaged? If so, your furnace in Portland may need certified services or installation by a professional technician.

Additional Troubleshooting Techniques for Common Furnace Startup Issues

Sometimes even after checking power supply, thermostat settings, air filters, and ignition components, your furnace may still refuse to start. In such cases, here are a few additional troubleshooting techniques you can try:

  1. Check the gas supply: Ensure that the gas valve is open and that there are no leaks or blockages in the gas line.

  2. Inspect the blower motor: A malfunctioning blower motor can prevent your furnace from starting. Listen for any unusual noises or vibrations coming from the motor.

  3. Reset the system: Turn off the power to your furnace and wait for a few minutes before turning it back on. This can sometimes reset any minor glitches in the system.

Remember, if these troubleshooting steps don’t solve the problem, it’s best to contact a professional HVAC technician. As a trusted HVAC company, we have the expertise and tools to diagnose and fix complex furnace issues. Our commercial HVAC services near me are designed to provide efficient and reliable solutions for all your heating needs.

Signs Indicating Need for Professional Furnace Repair or Replacement

We discussed possible reasons for a furnace not turning on, safety measures such as the safety switch on the furnace door and the safety float switch, checking ignition components, gas line and thermostat checks, circuit breakers, investigating limit switch functionality, and provided troubleshooting tips for DIY steps to try when your furnace won’t turn on.

By understanding these sections and following the steps outlined, you can gain valuable insights into identifying and potentially resolving issues with your furnace. However, when it comes to installation in Portland, it is important to note that some problems may require professional assistance. If you have tried all the suggested troubleshooting steps without success or if you are unsure about performing repairs yourself, it is recommended to contact a qualified HVAC technician who can accurately diagnose and address any underlying issues with your furnace.

Remember, proper maintenance and timely repairs are crucial in ensuring your furnace operates efficiently and safely. Regularly scheduling professional inspections can help identify potential problems before they escalate into costly repairs or replacements. Don’t hesitate to reach out to an expert when needed!


How often should I schedule maintenance for my furnace?

It is generally recommended to schedule annual maintenance for your furnace. Regular maintenance helps ensure optimal performance, extends the lifespan of your equipment, improves energy efficiency, and identifies potential issues early on.

What are some signs that indicate my furnace needs repair or replacement?

Signs that indicate your furnace may need repair or replacement include frequent breakdowns, insufficient heating output, unusual noises or odors coming from the unit, increased energy bills without changes in usage patterns, inconsistent temperature throughout your home, or if your furnace is more than 15 years old.

Can I perform repairs on my own if my furnace stops working?

While there are some basic troubleshooting steps you can try, it is generally recommended to leave furnace repairs to professionals. Furnaces involve complex systems and potentially hazardous components, so it’s best to rely on trained technicians from a reputable HVAC company who have the knowledge and experience to handle these repairs safely and effectively. When searching for commercial HVAC services near me, it’s important to find experts who can provide reliable and professional assistance.

How long does a furnace typically last?

The average lifespan of a furnace is around 15 to 20 years. However, this can vary depending on factors such as regular maintenance, usage patterns, and the quality of the equipment.

Is it necessary to replace my furnace if it’s still working but old?

While an older furnace may still be functioning, it may not be operating efficiently or providing optimal comfort. Upgrading to a newer, more energy-efficient model can help reduce your energy bills and improve overall heating performance. Consulting with an HVAC professional can provide valuable insights into whether replacing your old furnace is a worthwhile investment for your specific situation.

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