Mitsubishi Electric Heat Pump FAQ: Symbols, Inverter Not Heating, and How Heat Pumps Work

I spend a lot of time reviewing HVAC systems before they ship—wiring, labels, controller settings, actual heat output. After four years of this, I can tell you two things: most Mitsubishi Electric heat pumps work very well, and most problems people see are small. This FAQ covers the questions I hear most—including what those heat pump symbols mean, why an inverter system might not heat, how a heat pump compares to a simple baseboard heater, and when a fan actually helps.

What do Mitsubishi Electric heat pump symbols mean?

First, a caveat: Mitsubishi Electric uses different remote controls for different lines, and the icons can shift slightly by region and model. The basic set is pretty consistent.

• Sun — Heat mode.
• Snowflake — Cool mode.
• Water drop — Dry mode.
• Fan — Fan-only operation.
• Clock — Timer.

I've seen quite a few 'not heating' reports where the controller was simply in fan mode. If the display shows a fan icon and you expect heat, that's the first thing to fix. Newer thermostats sometimes show text instead of icons, but the heat symbol is usually a sun on standard Mitsubishi Electric remotes.

Why is my Mitsubishi Electric inverter not heating?

Start with the controller. The setpoint must be a few degrees above the current room temperature. If the room is 69°F and the controller says 68°F, the system won't heat. That's not a malfunction.

Next, check heat mode versus fan mode. I remember a batch of 16 units that all 'failed heating' in our quality area—the handheld controllers had been left in fan mode. Zero hardware faults. Look, I've done that too. It happens.

Then think about ice. In cold weather, the outdoor unit goes into defrost mode. You'll see steam rising from the coil, and the indoor airflow may feel cool for a while. A typical defrost cycle is 5 to 15 minutes. If it repeats every 20 minutes all day, that's more likely a refrigerant or maintenance issue.

One more thing: an inverter heat pump moves a large volume of air at a lower temperature. It won't blow furnace-hot air. If the air feels warmer than the room and the outdoor unit is running, the heating is probably working.

How does a heat pump work?

A heat pump doesn't create heat in the same way a baseboard heater does. It moves heat from one place to another. In heating mode, the outdoor coil extracts heat from the outside air, even when it's cold outside. Refrigerant absorbs that heat and evaporates; the compressor raises the pressure and temperature; then the hot gas enters the indoor coil. A fan blows indoor air across the coil, and warm air comes out.

A reversing valve is what switches the cycle between heating and cooling. In summer, the refrigerant direction reverses, and the indoor coil becomes the evaporator that absorbs heat from your room. In winter, the cycle runs the other way.

The inverter in Mitsubishi Electric units controls the compressor speed. Instead of starting and stopping full speed, the compressor slows down to hold the setpoint. Why does that matter? Because every start-up cycle wastes energy. Fewer cycles, less energy, quieter operation. This is where the efficiency difference starts.

Why does the fan on my heat pump keep running?

Sometimes that's normal. Some controllers are set to continuous fan, so the indoor fan runs even after the compressor stops, just to keep air moving. Other systems run the fan for a short time after heating to capture the residual heat in the coil. That's useful, not a fault.

Check whether the outdoor unit is also running. If the fan is on but the outside unit is off and the room hasn't reached the setpoint, you might have a fan timer setting or a relay issue. If the fan is on Auto and never stops, that's a reason to call a technician.

Heat pump or baseboard heater: which is more efficient?

Let's do the simple efficiency comparison. An electric baseboard heater converts electricity directly into heat: one unit of electricity in, one unit of heat out. A heat pump with an inverter compressor can often deliver two to three units of heat for every unit of electricity, because it moves heat from the outside air instead of generating it. According to the U.S. Department of Energy, heat pumps can provide roughly three times more heating energy than the electricity they use (Source: energy.gov, accessed 2025).

That advantage matters for whole-home heating, but I try not to be one-sided. Baseboard heaters are simpler, cheaper to install, and have no outdoor unit to worry about in winter. In a small room that only needs occasional heating, baseboard can still make sense. The 'baseboard is simple and basically the only choice' thinking comes from an era before variable-speed inverter compressors. For year-round comfort and running cost, a properly sized heat pump usually wins.

Can a fan help a baseboard heater?

Generally yes. A regular fan helps distribute the warm air that collects near the ceiling and pushes it back to the floor. That makes the room feel more even, but it doesn't change how much heat the baseboard produces. If you're using a fan with baseboard heat, aim it along the floor toward the middle of the room, not straight at the heater.

A heat pump has a different advantage. Its indoor fan pulls air through a filter and blows it directly across the indoor coil, circulating the whole room. That's why a heat pump can keep a room comfortable at a lower setpoint than a baseboard heater, even if the air leaving the indoor unit isn't as hot as the surface of a baseboard.

What should I check before calling a service technician?

Here's a checklist I give every customer who calls about a Mitsubishi Electric unit that stops heating:

• Confirm the controller is in Heat mode and the setpoint is above room temperature.
• Clean or replace the indoor air filter. This is the most common 'not heating' fix I see in service logs.
• Clear the outdoor unit of snow, leaves, or anything blocking the sides and top.
• Wait through one defrost cycle if the outdoor temperature is near or below freezing.
• Check airflow at the supply vents to confirm the indoor fan is circulating air.

In Q1 2024, more than a third of the 'not heating' tickets we reviewed were solved with a cleaned filter or a corrected controller setting. Nobody wants a service bill for a dirty filter, and good prevention starts with checking the easy stuff first.