Few things are more frustrating during the cold months than turning on your furnace and discovering that the furnace fan runs but no heat comes out. You may hear the blower running, feel the airflow, but the house remains cold. This problem, often described as “furnace blower working but no heat” or “furnace fan on but no heat”, can have multiple causes.
In this guide, I’ll walk you through why your furnace behaves this way, how it relates to the Goodman MBVK electric furnace, and practical troubleshooting steps to restore warmth efficiently and safely.
Understanding the Problem: Fan Runs but No Heat
When a furnace blower motor operates but the heat doesn’t come on, it indicates that the airflow system is functioning while the heating element or combustion process is not activating. In electric furnaces like the Goodman MBVK, this usually involves:
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Heat strips not energizing
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Thermostat malfunction
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Safety switches preventing operation
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Electrical issues or tripped breakers
Gas furnaces may have similar symptoms due to ignition failure or flame sensor problems. For homeowners, phrases like “furnace fan turns on but no heat” or “furnace fan works but no heat” describe the same frustrating scenario.
Goodman MBVK Electric Furnace Overview
The Goodman MBVK electric furnace is designed for efficiency, reliability, and ease of maintenance. Key features relevant to troubleshooting fan-only operation include:
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Modular electric heat strips – staged for energy efficiency
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ECM variable-speed blower motor – delivers consistent airflow
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High-limit safety switches – prevent overheating
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Thermostat interface – communicates call-for-heat signals
Because the MBVK separates airflow (blower) from heating elements, it’s possible for the fan to operate normally while the heat fails to engage.
Common Causes of Furnace Fan Running Without Heat
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Thermostat Issues
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Incorrect thermostat settings, miswired terminals, or faulty thermostat sensors can prevent heat signals from reaching the furnace.
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Ensure the thermostat is set to “Heat” and the temperature is above the current room temperature.
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Tripped High-Limit Switch
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Safety switches monitor furnace temperature and will shut off heat if overheating occurs.
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On the MBVK, a tripped high-limit switch can leave the blower running but no heat.
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Blown Fuses or Tripped Breakers
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Each heat strip requires a dedicated power circuit.
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A blown fuse or tripped breaker may disable one or more heat strips.
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Faulty Heat Strips
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Worn or damaged heat strips may fail to energize.
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Even if some strips work, the system may not produce noticeable heat.
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Control Board Malfunction
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The MBVK control board manages both the blower motor and heat stages.
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A board failure can leave the fan operational while preventing heat activation.
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Wiring or Connection Issues
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Loose or disconnected wires between the thermostat, control board, and heat elements can cause this problem.
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Diagnosing the Problem Step by Step
Step 1: Verify Thermostat Settings
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Set to “Heat” and confirm the set temperature is above room temperature.
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If using a programmable thermostat, check schedules and battery levels.
Step 2: Inspect the Breaker Panel
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Turn off the furnace breaker, then turn it back on.
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Check for tripped breakers or blown fuses for the furnace and heat circuits.
Step 3: Check Airflow and Filters
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Replace dirty air filters. Restricted airflow can trip high-limit switches, shutting off heat while keeping the blower running.
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Confirm that supply and return vents are unobstructed.
Step 4: Examine High-Limit Switches
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Locate the high-limit switch on the MBVK furnace (usually near the blower compartment).
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Press the reset button if tripped, but only after ensuring airflow is unobstructed. (HVAC.com)
Step 5: Test Heat Strips
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Electric furnaces like the MBVK have modular heat strips that can be individually tested.
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Use a multimeter to check for continuity across each strip.
Step 6: Inspect the Control Board
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Look for burnt components, loose connectors, or error indicators.
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Control board issues may require professional replacement.
Why the Blower Motor Keeps Running
Even when the furnace doesn’t heat, the blower motor often continues to circulate air. Reasons include:
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Maintaining airflow to prevent overheating
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Cooling the system after a high-limit trip
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Continuous fan setting on the thermostat
This design ensures safety and system longevity, even when heat isn’t available.
Differences Between Electric and Gas Furnaces
While the MBVK is an electric furnace, gas furnaces can show similar symptoms. Causes for furnace fan working but no heat in gas units include:
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Faulty ignition system
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Flame sensor issues
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Gas valve problems
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Control board errors
Electric furnaces simplify troubleshooting because there are no burners, flames, or combustion safety systems involved. (Energy.gov)
Safety Considerations
Before troubleshooting or working on a furnace:
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Turn off power at the breaker
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Use insulated tools when working near electrical connections
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Do not bypass safety switches
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Consult a licensed HVAC technician if unsure
Ignoring safety precautions can cause electric shock, component damage, or fire hazards.
Maintenance Tips to Prevent Fan-Only Operation
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Replace air filters regularly
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Inspect ductwork for obstructions
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Check thermostat batteries and wiring
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Schedule annual professional inspection
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Monitor breaker and fuse status
Preventive maintenance helps avoid scenarios where the furnace fan turns on but no heat is produced. (The Furnace Outlet)
When to Call a Professional
Call an HVAC technician if:
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The furnace fan runs but heat does not return after basic troubleshooting
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High-limit switch trips repeatedly
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There are unusual noises, burning smells, or sparks
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Control board or wiring issues are suspected
Professional service ensures safe, efficient repair without risking personal injury or furnace damage. (ACCA)
Summary: Solving Furnace Fan Runs But No Heat
When your furnace fan runs but no heat is produced, it’s usually a symptom of:
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Thermostat issues
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Tripped high-limit switches
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Blown fuses or breakers
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Faulty heat strips
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Control board or wiring problems
The Goodman MBVK electric furnace makes diagnosis simpler due to its modular design, separate blower operation, and safety features. By following step-by-step troubleshooting and regular maintenance, you can restore heat quickly and safely, keeping your home comfortable throughout the winter.
