When the temperatures drop in Northern Utah, a reliable furnace is essential for keeping your home warm and comfortable. But what happens when your furnace suddenly stops working or isn’t heating properly? Before you panic and call an HVAC professional, there are a few common issues you can troubleshoot on your own.

Many furnace problems have simple fixes that don’t require technical expertise. Checking your thermostat settings, replacing a dirty filter, or making sure your vents aren’t blocked could solve the issue and save you the cost of a service call. In this guide, we’ll walk you through some of the most common furnace problems and what you can do to fix them before reaching out to the experts at MTN Valley Heating & Air Conditioning.

1. Furnace Won’t Turn On

Few things are more frustrating than a furnace that refuses to turn on, especially on a cold Northern Utah night. Before assuming the worst, try this:

• Check the Thermostat: Make sure your thermostat is set to “heat” and that the temperature is set higher than the current room temperature. If the display is blank, it could be due to dead batteries or a tripped circuit breaker.
• Inspect the Circuit Breaker: A tripped breaker can cut power to your furnace. Check your home’s electrical panel and reset the breaker if needed. If it trips again, you may need professional assistance.
• Make sure the Furnace Switch is On: Many homeowners don’t realize their furnace has a power switch that looks like a regular light switch. Make sure it’s in the “on” position.
• Check the Pilot Light or Ignition System: If your furnace has a standing pilot light, it may have gone out and need relighting. For newer furnaces with electronic ignition, a sensor issue may prevent it from firing up.

2. Weak or No Airflow from Vents

If your furnace is running, but the airflow from your vents is weak—or worse, nonexistent—there may be a blockage or issue within the system. Here’s what to check:

• Dirty or Clogged Air Filter: A clogged air filter restricts airflow and forces your furnace to work harder, potentially causing overheating and system shutdowns. Replacing your filter every 1-3 months can prevent this.
• Blocked or Closed Vents: Walk through your home and make sure all vents are open and unblocked by furniture, curtains, or rugs. Restricted airflow can cause uneven heating and system strain.
• Blower Motor Issues: If your thermostat is on and the furnace is running but you’re not feeling air, your blower motor could be the issue. Check if you hear the fan running—if not, it will likely need professional repair.
• Leaky Ductwork: If airflow is weak in some rooms but strong in others, your ductwork may have leaks that need sealing. Over time, gaps or holes in the ducts can reduce efficiency and drive up energy costs.

3. Furnace is Blowing Cold Air

If your furnace is running but only blowing cold air, it can be uncomfortable and frustrating. Here are a few common reasons why this might happen and how to fix them:

• Check the Thermostat Settings: Make sure your thermostat is set to “heat” and not just “fan.” If the fan is set to “on” instead of “auto,” it will run continuously, even when the furnace isn’t heating.
• Pilot Light is Out (for Older Furnaces): If you have an older furnace with a standing pilot light, check to see if it has gone out. If it has, follow the manufacturer’s instructions to relight it. If it won’t stay lit, you may have a faulty thermocouple.
• Dirty Flame Sensor: A dirty or faulty flame sensor can cause the burners to shut off shortly after igniting, leading to cold air blowing from your vents. Cleaning the flame sensor with a soft cloth can sometimes fix this issue, but if it continues, professional service may be required.
• Overheated Furnace: If your furnace overheats due to a dirty air filter or restricted airflow, it may trigger a safety shut-off, stopping the burners while the fan continues running. Try replacing the air filter and opening all vents.

4. Furnace Turns On and Off Too Frequently

A furnace that cycles on and off too frequently—known as short cycling—can reduce energy efficiency and put unnecessary strain on the system. Here’s what might be causing it:

• Dirty Air Filter: A clogged air filter restricts airflow, causing the furnace to overheat and shut off prematurely. Replacing the filter is one of the easiest ways to prevent short cycling.
• Incorrect Thermostat Placement: If your thermostat is located near a heat source (like a fireplace, space heater, or direct sunlight), it may signal the furnace to shut off too soon. Consider relocating the thermostat or shielding it from heat sources.
• Blocked or Closed Vents: When too many vents are closed or obstructed, it can cause pressure imbalances in the system, leading to erratic cycling. Keep vents open to maintain proper airflow.
• Oversized Furnace: If your furnace is too large for your home, it may heat up the space too quickly and shut off before completing a full cycle. This can cause increased wear and tear on the system over time.

5. Unusual Noises Coming from the Furnace

If your furnace is making strange noises, it’s often a sign that something isn’t working properly. Here are some common furnace sounds and what they might mean:

• Loud Banging or Popping: This can happen when there’s a delayed ignition due to a dirty burner or when air ducts expand and contract suddenly. If the banging is coming from the furnace itself, it’s best to have it inspected.
• Squealing or Screeching: This usually indicates a worn-out blower belt or motor bearing. Lubricating the motor or replacing the belt can fix this issue.
• Rattling or Vibrating: Loose panels or components can cause a rattling sound. Tighten any screws or panels that appear loose, but if the sound persists, it could be a more serious issue with the blower motor or heat exchanger.
• Whistling or High-Pitched Hissing: This may indicate restricted airflow due to a dirty air filter or ductwork issues. Replacing the air filter or checking for duct leaks can help.

6. When to Call a Professional

While many furnace issues can be resolved with simple troubleshooting, there are times when you need to call in the experts. You should contact a professional if:

• Your furnace won’t turn on, even after checking the thermostat and power supply.
• The system is short cycling or frequently shutting off.
• You notice a persistent gas smell—this could indicate a leak and requires immediate attention.
• The pilot light won’t stay lit, or the ignition system isn’t working.
• You hear loud or unusual noises that don’t go away after basic maintenance.
• You’ve tried troubleshooting, but the furnace is still blowing cold air or not heating efficiently.

Contact MTN Valley Heating & Air Conditioning Today

We offer fast and reliable furnace repair services to keep your home comfortable all winter long. Whether your furnace won’t turn on, is blowing cold air, or making strange noises, our experienced technicians are here to help.

Need professional furnace repair? Contact MTN Valley Heating & Air Conditioning today to schedule a service appointment and make sure your heating system is running efficiently!