Few things cause more frustration for homeowners than realizing their HVAC system is running but not producing heat. You turn up the thermostat, hear the system engage, feel air coming from the vents — and yet the house stays cold. At that point, the question becomes unavoidable: why is my HVAC not heating?
Over the years, I’ve had countless conversations with homeowners facing this exact situation. Sometimes the fix is simple. Other times, the issue involves deeper system controls or safety logic that most people never see. In this article, I’ll walk you through the most common reasons an HVAC system not heating occurs, using the Goodman MBVK electric furnace as a reference point to explain how modern electric systems work, what can go wrong, and how to approach troubleshooting safely and logically.
Understanding What “HVAC Not Heating” Really Means
When homeowners say their HVAC isn’t heating, they’re often describing one of several different scenarios:
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The system runs but blows cool or lukewarm air
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The thermostat calls for heat but nothing happens
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The blower runs continuously without warmth
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Heat works intermittently
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The system shuts off shortly after starting
All of these fall under the umbrella of hvac system not heating, but they do not all have the same cause. The Goodman MBVK electric furnace helps illustrate why.
Unlike gas furnaces, electric furnaces rely entirely on electrical components—heating elements, sequencers, control boards, and blower motors—to generate and distribute heat. When any one of those components fails or behaves abnormally, the system may still run but fail to produce heat.
How the Goodman MBVK Electric Furnace Is Designed to Heat
Before diagnosing problems, it helps to understand how this system works.
The Goodman MBVK is a variable-speed air handler designed to pair with electric heat kits. When your thermostat calls for heat, several steps happen in sequence:
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The thermostat sends a heating signal
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The control board receives the call
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Electric heating elements energize in stages
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The blower ramps up to distribute warm air
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Safety switches monitor temperature and airflow
There is no flame, no pilot light, and no combustion chamber. That distinction matters greatly when diagnosing why an HVAC system is not heating.
For a technical overview of how electric air handlers function, Goodman provides detailed documentation within its product ecosystem, including the MBVK series overview available through their official product resources (https://www.goodmanmfg.com/products/air-handlers-and-coils/air-handlers/mbvk-series).
Common Reasons Your HVAC System Is Not Heating
Let’s walk through the most common causes I see in the field, starting with the simplest and moving toward more complex mechanical issues.
Thermostat Configuration Issues
One of the most overlooked reasons homeowners ask why is my HVAC not heating is improper thermostat configuration.
Check the following:
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Thermostat is set to HEAT, not COOL or AUTO
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Fan is set to AUTO, not ON
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Temperature is set several degrees above room temperature
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Programmable schedules are not overriding manual input
With electric furnaces like the MBVK, incorrect fan settings can create the illusion of cold air. If the fan is set to ON, it may circulate unheated air between heating cycles.
Power Supply and Electrical Issues
Because the MBVK is fully electric, power delivery is everything. A partial loss of power can leave the system running without heat.
Common electrical causes include:
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Tripped circuit breakers
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Blown fuses
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Loose wiring connections
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Failed sequencers or relays
Many electric furnaces use multiple breakers—one for the blower and one or more for the heating elements. If only one breaker trips, the blower may still operate, creating the impression that the HVAC system is running but not heating.
This is one of the most frequent reasons homeowners report an hvac system not heating condition.
High-Limit Switch Activation
Every electric furnace includes high-limit switches designed to protect the system from overheating. If airflow is restricted or internal temperatures rise too high, the system will shut off heating elements automatically.
Common causes include:
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Dirty air filters
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Blocked return vents
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Closed supply registers
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Failing blower motors
When this happens, the furnace may continue to move air without producing heat, leading homeowners to ask why their HVAC is not heating even though it seems “on.”
The U.S. Department of Energy highlights airflow restriction as a major contributor to heating inefficiency and system shutdowns in residential HVAC systems (https://www.energy.gov/energysaver/maintaining-your-heating-system).
Dirty or Restricted Air Filters
If there’s one maintenance task that solves more heating complaints than any other, it’s replacing the air filter.
A clogged filter reduces airflow, causing:
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Overheating of electric elements
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High-limit switch trips
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Reduced heat output
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Short cycling
In a Goodman MBVK system, airflow is critical because the variable-speed blower relies on feedback to maintain safe operating conditions. When airflow drops, safety systems intervene.
This often leads to calls where homeowners say, “My HVAC is running, but it’s not heating.”
Heating Element Failure
Electric furnaces depend on heating elements similar to those found in electric ovens or dryers. Over time, these elements can burn out or fail electrically.
Signs of a failed heating element include:
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Cold or lukewarm air
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One stage of heat working while others do not
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Tripped breakers
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Uneven heating
Because the MBVK uses staged electric heat, partial failures can be confusing. You may still get some warmth, but not enough to raise indoor temperatures effectively.
Control Board or Sequencer Problems
Modern electric furnaces rely heavily on electronic control boards rather than mechanical sequencers. If the board fails to energize heating elements in the correct order, the system may never produce heat.
Symptoms include:
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Blower runs continuously
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No heat even though thermostat is calling
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Inconsistent heating cycles
Control boards are not user-serviceable components. Diagnosis requires voltage testing and system knowledge, which is why professional evaluation is recommended.
Ductwork and Distribution Problems
Sometimes the furnace is producing heat, but it never reaches living spaces efficiently.
Common duct-related causes:
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Disconnected ducts
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Leaks in unconditioned spaces
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Poor insulation
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Collapsed flex duct
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Closed dampers
When airflow is compromised, homeowners assume the HVAC system is not heating, when in reality the heat is escaping elsewhere.
The Environmental Protection Agency emphasizes that duct losses can significantly reduce heating effectiveness and efficiency in residential systems (https://www.epa.gov/indoor-air-quality-iaq/duct-sealing).
Heat Pump Integration Confusion
Many Goodman MBVK units are installed as part of a heat pump system. In these setups, the electric furnace acts as auxiliary or emergency heat.
During mild weather:
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The heat pump does most of the work
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Supply air may feel cooler than expected
During colder weather:
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Electric heat engages automatically
This transition can confuse homeowners into thinking their HVAC system is not heating. In reality, the system may simply be operating in low-stage heat pump mode.
Understanding system staging and thermostat settings is critical when diagnosing perceived heating failures.
Why Electric HVAC Systems Feel Different Than Gas
A major reason homeowners ask why is my HVAC not heating after switching from gas to electric is perception.
Gas furnaces produce very hot supply air quickly. Electric furnaces produce steady, moderate heat that feels less intense but maintains temperature more evenly.
This difference often leads to unnecessary service calls even when the system is functioning normally.
For a broader explanation of electric versus gas heating characteristics, HVAC.com provides a useful comparison resource (https://www.hvac.com/resources/gas-vs-electric-furnace/).
When the System Cycles On and Off Frequently
Short cycling can also create the impression that an HVAC system isn’t heating properly. Causes include:
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Oversized equipment
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Faulty thermostat placement
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Airflow restrictions
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Electrical control issues
The Goodman MBVK’s variable-speed design helps reduce short cycling, but it cannot compensate for installation or configuration errors.
Signs You Should Call a Professional
While homeowners can check filters, breakers, and thermostat settings, some issues require professional diagnostics. Call a licensed HVAC technician if:
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Breakers trip repeatedly
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Heat works intermittently
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Burning smells appear
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Error codes display
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System shuts down unexpectedly
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Electrical components show signs of damage
The Consumer Product Safety Commission emphasizes professional service for electrical heating issues to prevent fire hazards and equipment damage (https://www.cpsc.gov/Safety-Education/Safety-Guides/Home/Heating-Safety).
Why the Goodman MBVK Is Still a Strong Choice
Despite troubleshooting scenarios, the Goodman MBVK remains a reliable and efficient electric furnace when properly installed and maintained. Its strengths include:
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Variable-speed airflow for comfort
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Compatibility with modern thermostats
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Quiet operation
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Strong safety controls
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Flexible configuration options
When homeowners understand how the system works, many “HVAC not heating” concerns turn out to be normal operating behavior or minor maintenance issues.
Final Thoughts from Mike Sanders
If you’re asking why is my HVAC not heating, start with the basics. Confirm thermostat settings, airflow, and power supply before assuming major failure. Electric furnaces like the Goodman MBVK operate differently than gas systems, and understanding those differences makes all the difference.
A properly installed and maintained electric furnace delivers steady, reliable comfort. Most problems stem from airflow restrictions, electrical interruptions, or misunderstandings about how modern HVAC systems operate—not from major equipment failure.
When in doubt, get a professional involved early. Small issues caught early prevent expensive repairs later and keep your home comfortable when you need it most.
