If there’s one thing that drives homeowners absolutely nuts in winter, it’s inconsistent heat. I’ve lost count of how many calls start with some version of the same complaint: “Mark, my furnace blows cold air then hot,” or “My heater blows cold air then hot—what’s going on?”
These aren’t new problems, but as more homeowners switch to high-efficiency electric systems like the Goodman MBVK electric furnace, the way those problems show up—and the way we explain them—has changed.
Let me be clear right up front: in many cases, what you’re experiencing is normal operation, not a defect. In other cases, it’s a sign that something needs attention before it turns into a real comfort or reliability issue. The key is knowing the difference.
In this article, I’m going to break down how the Goodman MBVK works, why temperature swings happen, and exactly why does my furnace blow hot air then cold is such a common question with modern electric furnaces. I’ll also explain when you should stop worrying—and when you should pick up the phone and call a professional.
A Quick Overview of the Goodman MBVK Electric Furnace
The Goodman MBVK is not your grandfather’s furnace. It’s a multi-position, variable-speed electric furnace designed to pair seamlessly with modern heat pumps and air handlers. It’s built for efficiency, comfort, and flexibility, especially in regions where electric heating makes sense.
What sets the MBVK apart is its variable-speed ECM blower motor. Unlike older single-speed blowers that were either on or off, this motor ramps up and down gradually. That one feature alone explains a large percentage of the “temperature confusion” homeowners experience.
The MBVK is also designed to work in staged heating modes, particularly when paired with a heat pump. That means it doesn’t always blast full heat immediately—and that’s intentional.
Goodman didn’t design this system to feel dramatic. They designed it to feel efficient, even, and controlled. Sometimes, though, that design clashes with what homeowners expect heat to feel like.
Why “Cold Air” Isn’t Always Cold
Let’s tackle the biggest misconception first.
When someone tells me their furnace blows hot then cold, nine times out of ten the “cold” air isn’t actually cold. It’s air that’s closer to room temperature than the previous heated air. Your skin notices the difference, and your brain translates that difference as a problem.
With a variable-speed system like the MBVK, airflow often continues after the heating elements cycle off. The blower is designed to squeeze every last bit of usable heat out of the system. That means you’ll feel warm air, then neutral air, then eventually cooler air—all in one cycle.
This is especially noticeable if:
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You’re standing near a vent
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The room was already warm
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The system is running on a low heating stage
In other words, your furnace isn’t confused. It’s being efficient.
Furnace Blows Cold Air Then Hot: What’s Really Happening?
When someone says their furnace blows cold air then hot, the order of operations matters. With the Goodman MBVK, this usually happens during system startup.
Here’s the sequence:
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The thermostat calls for heat
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The blower motor starts at a low speed
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Heating elements energize seconds later
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Air temperature gradually increases
That initial airflow before the elements fully engage can feel cool—especially on a cold morning. Older furnaces delayed the blower until the heat exchanger was already hot. The MBVK prioritizes airflow management and system protection, so the blower may start earlier.
Is that a flaw? No. It’s a design choice aimed at extending component life and improving efficiency.
Heater Blows Cold Air Then Hot in Heat Pump Systems
If your MBVK is paired with a heat pump, the situation gets even more interesting.
Heat pumps don’t create heat—they move it. When outdoor temperatures drop, the heat pump may struggle to keep up. During these times, the system may switch between:
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Heat pump operation
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Electric resistance backup heat
That transition can feel like a temperature swing. Homeowners often describe this as “my heater blows cold air then hot.” What they’re really feeling is the system shifting from one heat source to another.
According to the U.S. Department of Energy, heat pumps are most efficient when they run steadily at lower output rather than cycling aggressively, which explains why airflow may feel different than what you’re used to with fossil-fuel systems. This is well documented in their overview of how heat pumps operate.
The MBVK is designed to support that steady operation, even if it feels unfamiliar at first.
Furnace Blows Hot Then Cold: When It’s Normal
Let’s flip the order.
When a homeowner says their furnace blows hot then cold, I start by asking one simple question: How long does the “cold” last?
If it’s brief—30 seconds to a couple of minutes—there’s a good chance nothing is wrong.
Here’s why:
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The thermostat reaches setpoint
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Heating elements shut off
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Blower continues running to dissipate residual heat
That leftover airflow cools down gradually. The MBVK’s variable-speed motor makes this transition smoother, but it also makes it more noticeable.
This is not short cycling. This is not a malfunction. This is the system doing exactly what it was designed to do.
When Hot-Then-Cold Air Is a Problem
That said, not every case gets a free pass.
If your furnace blows hot then cold repeatedly and never seems to maintain temperature, that’s when we start digging deeper.
Possible issues include:
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Incorrect thermostat configuration
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Undersized heating elements
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Airflow restrictions
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Improper staging setup
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Duct leakage
The MBVK is highly configurable, and that’s a double-edged sword. When it’s set up correctly, it’s outstanding. When it’s not, comfort suffers.
Goodman provides extensive technical documentation for proper setup, but configuration still requires real-world experience. That’s why professional installation matters more with variable-speed equipment than it ever did with old-school furnaces. This emphasis on proper installation aligns with broader HVAC best practices outlined by organizations like ACCA in their system design standards.
Why Does My Furnace Blow Hot Air Then Cold? The Thermostat Factor
If I had to point to one overlooked cause of temperature swings, it would be the thermostat.
Modern electric furnaces like the MBVK don’t play well with outdated or improperly programmed thermostats. A thermostat that’s set up for a gas furnace may shut off heating stages too aggressively or fail to coordinate properly with a variable-speed blower.
Common thermostat-related issues include:
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Incorrect cycle rate settings
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Missing heat pump parameters
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Improper staging delays
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Poor placement in the home
When homeowners ask, “why does my furnace blow hot air then cold?” the answer often lives on the wall, not in the furnace cabinet.
The Role of Airflow and Duct Design
Here’s another truth that doesn’t get enough attention: the furnace is only as good as the duct system attached to it.
The MBVK moves air differently than older systems. If your ductwork was sized for a single-speed blower, airflow may be uneven. That can exaggerate temperature swings and make normal operation feel like a problem.
Signs of duct-related issues include:
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One room heating faster than others
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Strong airflow at some vents, weak at others
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Temperature complaints that change by room
Energy Star has long emphasized the importance of proper duct sealing and airflow balance for comfort and efficiency, especially in high-efficiency systems.
This is not a Goodman problem. This is a system design problem.
Electric Furnaces Feel Different—And That’s Okay
One thing I always tell homeowners is this: electric heat feels different than gas heat.
Gas furnaces deliver short bursts of very hot air. Electric furnaces deliver longer cycles of moderately warm air. Neither is “better,” but they feel different on your skin.
When you switch to an electric system like the MBVK, your expectations may need a reset. That adjustment period is often when people start searching phrases like furnace blows cold air then hot or heater blows cold air then hot.
Understanding how your system is supposed to behave goes a long way toward peace of mind.
When to Call a Professional
Here’s my rule of thumb.
Call a professional if:
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The air is truly cold for extended periods
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The system short cycles constantly
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Your energy bills spike unexpectedly
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You hear unusual electrical or blower noises
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The system never reaches set temperature
Do not call just because the air temperature changes slightly during a cycle. That’s normal for the MBVK.
A qualified technician will check staging, airflow, thermostat programming, and electrical performance before declaring a problem.
Final Thoughts from the Field
The Goodman MBVK electric furnace is a solid, well-engineered piece of equipment. Most of the complaints I hear about temperature swings aren’t failures—they’re misunderstandings.
When someone asks me why their furnace blows hot then cold, or why their heater blows cold air then hot, my answer usually starts with education, not repair.
Modern systems are smarter, more efficient, and more nuanced than ever before. The challenge is that comfort isn’t always intuitive. Once you understand how your furnace thinks, the anxiety fades—and so does the urge to stand over the vent wondering what’s wrong.
If you’re experiencing inconsistent heat, don’t panic. Learn the system. Verify the setup. And when in doubt, get a professional set of eyes on it.
That’s how you get the comfort you paid for—and the peace of mind you deserve.
