Common Reasons For Furnace Breakdowns: The Complete Guide


We all know that feeling. When that big investment is working, but not working properly. The squealing in your car. The jumpy TV screen. The noise in your furnace. It seems well enough to work — but doesn’t seem well enough to last.

Like any other major investment in your life – car, home entertainment center, margarita maker – different furnace makes and models have advantages, disadvantages, and differences on results.

Often times in the event of a furnace breakdown (or heat pump issue), homeowners call HVAC services in a panic. Customers are charged a diagnostic service fee, and an emergency service charge if they feel like they they need immediate help. Sometimes, it’s as simple as bad thermostat batteries or a clogged air filter.

Using This Page As Your Furnace/Heat Pump Breakdown Guide


If you are having issues with your gas furnace or electric heat pump, there’s a good chance it’s listed below –– from how to solve it, to immediate steps you can take to remedy the situation and what you should expect to pay.

Are you thinking about investing in a new furnace or heat pump? Home Advisor has a great guide to help you choose what’s right for you. While a furnace may have more safety concerns, a heat pump issue is more costly to fix. 

Cost Key:

$ – DIY
$$ – low $100’s
$$$ – high $100’s to low $1,000
$$$$ – many $1,000’s/full replacement

Gas Furnace Problems 


Many natural gas furnaces are in it for the long haul. They can operate efficiently for up to 20 years. In Northern California, where winter months are not severe, purchasing the most expensive furnace may not be necessary.

The biggest issue with natural gas furnaces? It has always been, and will be, safety hazards. Along with being combustible, natural gas leaks can leave your home susceptible to carbon monoxide poisoning. Most homes come equipped with a carbon monoxide detector. If you don’t have one, you GET one!  They cost just over a $20 on Amazon. However, if a furnace is installed correctly, it should also have a backup protection system, preventing harmful elements from entering your home.

My Gas Furnace Won’t Kick On

One of the biggest reasons for a furnace breakdown may not even take a trip to the basement to fix – your thermostat. Often times, homeowners make meaningless service calls only to later discover their heating function wasn’t switched on, or an older thermostat unit ran out of batteries. The same can be said about your power grid. Make sure your breaker isn’t tripped off. Other problems to look for:

  • Gas supply. If there is a disruption to your gas supply, your furnace will not work.
  • Pilot light. If you can not re-light it, you may have an issue with the sensor or assembly.
  • Your furnace has an ON/OFF switch. Locate it to ensure its in the ON position.
  • Condensate pan. If the condensate pan is full, your furnace will not run.
  • If the blower motor isn’t working, you will need a replacement part.
  • Make sure the ventilation pipe on the side of your home or your roof is clear of debris/ice.

Looking for help? Check out our DIY Widget on our maintenance page! Don’t forget to get a tune-up every year — especially if your gas furnace is an older model. 

Cost to Repair Furnace: $-$$

If your furnace is not turning on, thermostat and breaker issues can be DIY fixes. Turn your furnace to 5-10 degrees higher than your normal room temperature. 

Repairing a pilot light sensor or thermocouple might require a service call, but it’s not a major repair. A blower motor carries a similar quote, though a full replacement might cost hundreds of dollars.

For more information, check out this video —————->

My Furnace Is Not Blowing Hot Air

Again, the thermostat is your first order of recourse. If your furnace is set to ON instead of AUTO, it may be running the fan in its normal cycle. 

A common cause is a dirty air filter. Don’t forget to change your air filters regularly – especially if you live with a family and/or pets. A dirty air filter will block air flow and cause the furnace to overheat.

A furnace overheating too often can ruin your heat exchanger, which can be a major issue.

Cost To Repair Furnace Not Blowing Hot Air: $-$$$$

In most instances of your furnace not blowing hot air, a thermostat issue or air filter problem is something you can take care of on your own. But a cracked heat exchanger is like a needing a transmission replacement in your vehicle. It is a labor-intensive component that could cost thousands to replace.

My Gas Furnace is Making a Noise

Is it cranking, pounding, grinding, hissing, whining? Whatever it is, ignoring these noises, seemingly harmless as most could be, may cost you. Some common examples

Bang – This can happen when your burners are dirty, and the gas builds up, delaying the ignition until it finally lights. This can be an issue, as small gas explosions like this can crack your heat exchanger.

This sound also happens when your ducts expand. Your duct system may not be sized properly or needs better support, your vents are closed, or you have a dirty air filter.

Grind – This may be an issue with your squirrel cage blower wheel. It could be lose or the mount could be broken.

Whine – This can be a blower belt issue. Your shaft bearings need lubricated, or you have a bad blower motor.

For more information on strange furnace noises, check out this sponsored content from A.J. Perri, a home services provider on the USA Today Network.

Cost to Repair Furnace Making A Noise: $-$$$

A variety of furnace noises can bring about a variety of service costs. Generally, blower wheel/motor fixes or replacements run in the hundreds. If your duct system is an issue, talk to your insurance company, particularly if you inherited the home recently. A new duct system can cost thousands of dollars.

My Gas Furnace Won’t Shut Off

Check your air filter and thermostat. Your furnace may need to continuously run to provide heat because the airflow is blocked, or your thermostat may simply be in the ON position.

Other issues could include a fused contact, or a control board short-circuit.

Cost to Repair Furnace Not Shutting Off: $-$$$

You can purchase control boards online and replace them yourself for about half the cost of a service technician, but you do run the risk of sacrificing quality.

My Gas Furnace Pilot Light Is Out

Furnaces that have them have instructions on how to light the pilot light. Check for a gas supply issue by testing your faucet and stove (if it is gas-powered). If your furnace pilot light works and then keeps burning out, you might have a thermocouple malfunction.

Cost To Repair Pilot Light Out: $-$$

Newer furnaces do not have pilot lights. If a home you recently purchased has a furnace with a pilot light, it could be more than 10 years old and require routine maintenance.

Furthermore, it might be costing you more to run over the course of its lifetime than it would be to install a new furnace. Moore has financing and rebates available to suit the needs of any homeowner!

For more information, check out this video —————->





My Home Smells Like Gas

Natural gas is actually odorless and tasteless, which is why you should have a carbon monoxide detector in at all times. The smell of mercaptan (rotten eggs) often accompanies this as an additive to help residents detect leakage.

If you smell this, turn off your gas supply and gas-using appliances immediately and extinguish all flames, ventilate the area, and call your gas provider.

Cost To Repair Home Smelling Like Gas: $-$$$$

Gas is typically a publicly owned entity, so the onus is likely on your gas company to fix the issue. However, if you have a leak inside the home, it depends. A leak to an appliance can be a couple hundred, but a mainline can cost thousands.

My Gas Furnace Is Cycling Too Frequently, Repeatedly, or Short-Cycling

Poor thermostat placement can be a common cause of short cycling. If your thermostat is near a heat source, it could mis-read the actual temperature of your home. Another common issue is an oversized furnace that pumps too much heat into a home in an unequal fashion.

Other things to watch for include dirty air filters and rusted flame sensors.

Cost to Repair: $-$$$

Replacing a flame sensor can cost hundreds of dollars, and is not recommended as a DIY fix. Thermostat replacement costs can vary in the low hundreds, but if you are savvy enough to attempt a DIY fix in your house, it might require little to nothing at all.

Electric Heat Pump Problems


In moderate temperatures Northern California experiences throughout the year, electric might be the best option. It operates at the highest efficiency, and offers the lowest installation costs. However, if you live in an area where the temperature could dip below freezing, an electric heat pump loses its effectiveness. It’s important to note that PG&E rates for electric(kWh) are less than for gas (therm).

My Heat Pump Doesn’t Run at All

You can DIY common issues for an outdoor unit that is not running. This includes a thermostat not being set properly, an emergency shut-off switch or blown fuse/circuit breaker. Check your condensate pump to make sure it’s not unplugged.

However, issues that might require a service call include a broken contactor/capacitor, control module, bad cable/wiring or a faulty relay.

Cost: $-$$

Blown fuses and improperly functioning thermostats can be DIY fixed, however, many of the other fixes can range in the low- to mid-hundreds.

 Thermostat malfunctions are a common cause of heat pump issues. To just make sure it’s sending a signal, set it at 5 degrees higher than your typical setting. Make sure your wires are properly mounted on their respective screws. 

Need a New Thermostat? 

Ask us about our ENERGY STAR Certified Thermostats by Honeywell®

You can save through the Energy Upgrade California program.

Get a $75 kicker incentive when you have Moore Home Services install an ENERGY STAR Certified Thermostat by Honeywell®.

My Heat Pump Freezes

If your heat pump is covered in ice, shut it down! A couple things you can do on your own include:

  • Changing your dirty filters
  • Checking your indoor air registers to ensure they’re not blocked
  • Clean away debris that could be preventing airflow
  • Check your gutters – clogged gutters could cause water overflow on your outside unit.
  • Add refrigerant or replace the defrost timer.

Cost To Repair Frozen Heat Pump: $-$$

Typically, a frozen heat pump is due to external factors. A simple air filter change or gutter cleaning could free up the flow of air. Adding refrigerant or replacing a defrost timer can be a tad more expensive, but it shouldn’t break your bank.

My Heat Pump Blower Doesn’t Work

This is likely an issue with the limit switch located below the plenum (the box that gives heat to your duct system), or a thermostat problem. You can change your heat pump limit switch, which is designed to shut off when the plenum gets too hot.

See your instruction manual for details or make a service call to reset the pointers on the fan side of the limit control.

If the blower motor is running but there’s no air, you probably have a belt issue.

Cost To Repair Heat Pump Blower: $-$$

A fan limit switch or thermostat typically cost under $100.

Heating System Repairs

Heat pump issues? One of the first things you should check is your thermostat.

My Heat Pump Is Short- or Long-Cycling

Your outside unit may be overheating. Check your air filters and thermostat. It is possible your thermostat isn’t properly calibrated or has been placed too close or far from a heat source.

Cost: $-$$$$

An overheating unit could require a replacement, however, a simple thermostat fix can be taken care of quite easily. 

My Heat Pump Makes Odd Noises

Squealing/Grinding Noise – you might have an issue with the motor bearings. This isn’t a DIY fix. Call us!

Rattling – your heat pump’s cover panel might be loose, or your ductwork isn’t well connected. This might be a DIY fix, depending on where your loose ductwork is located. Knowing where to find it might require an expert, though. It depends on how long you’ve lived in your home, and how well you know the layout. 

Popping Noise – this sound is possibly expansion from your ductwork. This sound can be very common, especially in cold months when pressure contracts your ducts. It’s likely not a major issue, but check with your local HVAC contractor to make sure. Each home is structurally different. 

Cost: $-$$$

Simple noises don’t always require an immediate fix. But if you are in need of new ductwork, you could be facing an expensive project – up to $55/linear foot. 

Mathematical Evidence: Save Your Investment With Maintenance 


Here’s something to think about. Maybe you could get away for a year without changing the oil on your car. 

But would you pay a couple hundred dollars annually to ensure that car lasted an extra three, five, or even seven years? The eventual thousands you’d save on major repairs, or purchasing a new vehicle years earlier than you’d prefer, more than balance the short-term spend. 

The best way to ensure you’re not revisiting your furnace issues is to get routine maintenance. Moore Home Services recommends getting your system checked once per year. Want to make it easy? Schedule an appointment today or check out our Gold Club for year-over-year benefits. 

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