Few things create more frustration for a homeowner than realizing the house is cold while the thermostat insists the system is running. When you hear “the fan is on, but there’s no heat,” or you start asking yourself why is my HVAC not heating, you’re not alone. This is one of the most common service calls technicians receive every winter.
In this guide, I want to walk you through the real-world causes behind an HVAC system not heating, using the Goodman MBVK electric furnace as our reference platform. Along the way, we’ll break down what actually happens inside an electric furnace, how heating commands are processed, where failures tend to occur, and how to separate simple fixes from problems that require professional attention.
This article is written to help homeowners, property managers, and HVAC professionals understand why heating stops working, how to diagnose the most common issues, and what makes the MBVK platform particularly well-suited for stable, dependable electric heat.
Understanding the Question: “Why Is My HVAC Not Heating?”
When someone says my HVAC is not heating, they’re usually describing one of several scenarios:
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The system turns on, but only blows cool or room-temperature air
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The thermostat calls for heat, but nothing happens
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The unit starts and stops quickly
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The blower runs continuously with no warmth
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The system worked yesterday but not today
These symptoms all fall under the broader category of HVAC system not heating, but the causes vary depending on system type, wiring, airflow, and safety controls.
With electric furnaces like the Goodman MBVK, the troubleshooting logic is more straightforward than with combustion-based systems. There is no gas pressure, flame sensing, or venting — but that doesn’t mean failures can’t occur.
The Goodman MBVK Electric Furnace: A Quick Overview
Before diving into failures, it helps to understand how the Goodman MBVK is designed to work.
The MBVK is a variable-speed electric air handler that becomes a full electric furnace when paired with electric heat kits. Its core components include:
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A variable-speed ECM blower motor
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Electric resistance heating elements
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A control board that manages staging and safety logic
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Temperature and limit sensors
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Airflow and safety interlocks
Unlike gas furnaces, the MBVK does not burn fuel. Instead, it converts electrical energy directly into heat through resistance elements, achieving near-100% point-of-use efficiency.
Goodman’s documentation and distributor education resources such as those available through Goodman's website emphasize that proper airflow and correct electrical configuration are essential for reliable heating performance.
How Heating Is Supposed to Work in an Electric HVAC System
To understand why your HVAC is not heating, you need to understand the sequence of operation.
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The thermostat calls for heat
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The control board receives the signal
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Heating elements are energized in stages
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The blower motor ramps up
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Warm air is delivered through ductwork
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Safety switches monitor temperature and airflow
If any part of this chain breaks, heating will stop — sometimes silently.
Unlike gas systems, electric furnaces rarely “lock out,” but they do shut down heating circuits when unsafe conditions are detected.
The Most Common Reasons an HVAC System Is Not Heating
Let’s walk through the most frequent root causes I see when homeowners say “my HVAC is not heating.”
1. Thermostat Configuration Errors
Before assuming mechanical failure, always start at the thermostat.
Common thermostat-related issues include:
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System set to “cool” instead of “heat”
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Fan set to “on” instead of “auto”
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Incorrect system type selected
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Dead or weak batteries
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Faulty wiring connections
Many modern thermostats allow configuration for gas, electric, or heat pump systems. If the wrong system type is selected, the furnace may never receive a proper call for heat.
This is a surprisingly common cause of HVAC system not heating complaints and is often resolved in minutes.
2. Power Supply or Electrical Interruptions
Electric furnaces require significant electrical input. If part of that supply is interrupted, heating will not occur.
Check for:
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Tripped breakers
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Blown fuses
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Loose electrical connections
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Power interruptions to the air handler
Even if the blower runs, heating elements may be on a separate breaker. This can lead to a situation where the system appears “on” but produces no heat.
Electrical reliability is one reason manufacturers stress proper installation and inspection, as outlined in homeowner safety guidance from sources like HVAC.com.
3. Dirty or Restricted Airflow
Airflow problems are one of the most underestimated causes of HVAC heating failures.
If airflow is restricted, safety switches may shut down the heating elements to prevent overheating. This leads homeowners to believe their HVAC system is not heating, when in reality it is protecting itself.
Common airflow issues include:
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Dirty or clogged air filters
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Closed or blocked supply vents
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Obstructed return grilles
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Collapsed or undersized ductwork
The Goodman MBVK relies on precise airflow to regulate its staged heating system. When airflow drops below design thresholds, limit switches open and disable heating.
According to HVAC airflow standards referenced by organizations such as ACCA, improper airflow is one of the most common root causes of comfort and performance complaints.
4. Heating Element Failure
Electric furnaces depend entirely on heating elements. If one or more fail, heating output drops or disappears.
Common signs of heating element problems:
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Blower runs but air is cool
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Heat works intermittently
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Breakers trip when heat engages
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System heats briefly then shuts off
The Goodman MBVK uses staged heating elements, meaning multiple elements activate depending on demand. If one element fails, the system may still operate at reduced capacity, confusing homeowners into thinking the HVAC is partially working.
Over time, heating elements can degrade due to thermal stress. While they are designed for long life, replacement is sometimes unavoidable.
5. Safety Limit Switch Activation
Every electric furnace includes safety limit switches designed to shut off heating if temperatures exceed safe levels.
Common triggers include:
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Restricted airflow
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Dirty filters
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Blocked ductwork
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Failed blower motor
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Electrical issues
When a limit switch opens, heating stops until temperatures return to normal. In some cases, the switch automatically resets; in others, it requires professional inspection.
This is a major reason homeowners report that their HVAC system is not heating “sometimes but not always.”
6. Control Board or Relay Issues
The control board is the brain of the Goodman MBVK. It manages:
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Thermostat communication
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Heating stage sequencing
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Blower timing
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Safety logic
If relays or control circuits fail, heating may not activate even though power and airflow are present.
Symptoms of control board issues include:
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No response to thermostat calls
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Erratic operation
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Heat only working after power reset
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Clicking without heating
Control boards are sensitive to voltage fluctuations and wiring errors. Diagnosing them requires proper testing tools and experience.
7. Improper Installation or Configuration
Even a high-quality system like the MBVK can underperform if improperly installed.
Installation-related causes of HVAC not heating include:
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Incorrect breaker sizing
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Improper wiring of heat kits
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Incorrect airflow configuration
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Mismatched thermostat
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Duct sizing errors
This is why manufacturers and distributors emphasize correct setup procedures, such as those outlined in installation guidance provided by distributors like This Old House.
8. Seasonal Transition Issues
Many heating complaints appear at the beginning of cold weather. Systems that sat unused for months may reveal issues once activated.
Common seasonal problems:
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Dust buildup on elements
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Electrical contacts oxidized
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Filters clogged since last season
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Thermostat programming errors
Running a pre-season test and inspection helps catch these issues before cold weather sets in.
9. What Makes the Goodman MBVK Reliable When Properly Maintained
Despite all the potential issues listed above, the MBVK remains a strong performer when installed and maintained correctly.
Key design advantages include:
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Variable-speed ECM blower for airflow consistency
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Staged electric heat for efficiency
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Advanced safety monitoring
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Flexible installation options
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Compatibility with modern thermostats
These features help reduce the likelihood of nuisance shutdowns and uneven heating.
Industry guidance from organizations such as Energy.gov highlights that properly maintained electric heating systems can provide consistent comfort with minimal intervention.
10. A Step-by-Step Approach When Your HVAC Is Not Heating
Here’s a practical troubleshooting sequence I recommend:
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Confirm thermostat mode and temperature setting
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Check breakers and electrical supply
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Replace or clean air filters
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Ensure all vents are open
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Listen for blower operation
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Observe whether heat ever engages
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Look for flashing diagnostic indicators
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Call a professional if heating still does not engage
Avoid repeatedly cycling power or bypassing safety switches — doing so can cause damage or create unsafe conditions.
11. When to Call a Professional Technician
You should contact a licensed HVAC technician if:
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Heating never activates
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Breakers trip repeatedly
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You smell burning or electrical odors
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The system short-cycles
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You see error codes you cannot interpret
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Heat works intermittently
Professional technicians have the tools to test resistance, voltage, and airflow accurately — all essential for diagnosing electric furnace issues.
12. Final Thoughts from Jake Lawson
When homeowners ask, “Why is my HVAC not heating?”, the answer is rarely just one thing. Heating systems are interconnected networks of electrical, mechanical, and airflow components. The Goodman MBVK electric furnace is a solid, reliable platform, but like any system, it depends on proper installation, airflow, and maintenance to perform as intended.
If your HVAC system is not heating, approach the issue methodically. Start with the basics, understand how your system is designed to work, and don’t ignore early warning signs. Most heating problems are solvable — and many are preventable.
