How To Troubleshoot Weak Heating And Check Auxiliary Heat Strips

When the cold sets in, a heat pump becomes the unsung hero of indoor comfort—quietly maintaining a steady, warm temperature. But when it starts blowing lukewarm air or just doesn’t seem to keep up, frustration quickly builds. One of the most common reasons for this issue lies in a part that many homeowners overlook: the auxiliary heat strips.

This article breaks down what auxiliary heat strips are, why they matter, and how you can safely check them when your heat pump isn’t delivering enough warmth.

Understanding the Role of Auxiliary Heat

The Backup Behind the Warmth

Heat pumps are designed to transfer heat from outside air into your home. This process works efficiently most of the time, but as the temperature drops, the system can struggle to extract enough heat from the cold air. That’s when auxiliary heat (often called “emergency heat”) kicks in.

Auxiliary heat uses electric resistance heating elements, also known as heat strips, to supplement the heat pump’s output. They act like an electric furnace, boosting the system’s heating capacity during frigid conditions or when the pump alone can’t meet the thermostat’s demand.

Why Heat Strips Are Essential

Without auxiliary heat, your home might feel chilly on extremely cold mornings. These strips are especially important in regions that experience significant temperature swings. They ensure consistent comfort, protect the system from overworking, and maintain energy efficiency—when functioning properly.

Signs That Your Heat Pump Isn’t Heating Properly

Before diving into the technical checks, it’s helpful to identify symptoms that suggest a possible issue with the heat strips. Some of the most common warning signs include:

• Cool or lukewarm air from vents: The system runs, but the air never feels truly warm.
• Extended heating cycles: The heat pump runs continuously without reaching the desired temperature.
• Spike in energy bills: A malfunctioning heat strip can cause the system to rely too heavily on inefficient backup modes.
• “AUX” or “EM HEAT” light stays off: Most thermostats show when auxiliary heat is active; if the light never comes on, the strips may not be engaging.

If you notice one or more of these signs, it’s time to check whether the auxiliary heat is working as it should.

Step-by-Step: How to Check Auxiliary Heat Strips

While some diagnostic steps should be left to a professional, there are several safe and simple ways to determine whether your auxiliary heat is functioning.

1. Check the Thermostat Settings

Start with the basics. Set your thermostat a few degrees higher than the current indoor temperature—say, from 68°F to 72°F. Wait for a few minutes and listen for the system to shift gears. On most thermostats, an indicator (like “AUX” or “HEAT ON”) appears when the auxiliary heat activates.

If that indicator never appears, even as the system struggles to warm the home, the problem could lie within the heat strips or their control system.

2. Listen and Feel for Temperature Changes

When the auxiliary heat engages, you should notice a subtle change in sound and temperature. The air coming from the vents should feel noticeably warmer, and the system may sound slightly different as the strips activate.

If the airflow feels unchanged—especially if it’s still cool—there’s a good chance the strips are not heating properly.

3. Inspect the Air Handler

Warning: Only attempt this step if you’re comfortable working around electrical equipment and know how to turn off the power safely.

Locate the air handler, which houses the heat strips. Before opening any panels, switch off power to the unit at the circuit breaker. Once it’s safe, remove the access panel and look for the metal heating elements. Signs of damage—such as corrosion, broken coils, or burnt wiring—can indicate a malfunction.

If everything looks intact, you can visually check for signs of overheating or debris buildup that might restrict performance. Do not attempt to test the electrical components without proper tools and training.

4. Test the Heat Strips with a Multimeter

If you’re comfortable using a multimeter, you can check the continuity of each heating element. With power still disconnected, place the meter’s probes on each terminal of the heat strip. A reading that shows no continuity means the strip is faulty and will need replacement.

This test also helps confirm whether the problem is mechanical (like a damaged element) or electrical (like a control board or relay issue).

5. Examine the Breakers and Fuses

Heat strips draw significant power. If a breaker trips or a fuse blows, the auxiliary heat won’t activate at all. Check the circuit panel and reset any tripped breakers. However, if they continue to trip, that’s a strong indicator of an underlying electrical problem that requires a technician’s attention.

When to Call a Professional

Even if you’re comfortable with basic maintenance, heat strip issues often require professional service. A licensed HVAC technician can run in-depth diagnostics, such as checking voltage to the strips, inspecting relays, and verifying the thermostat’s control signals.

In some cases, the strips themselves might be fine, but the control board or sensors could be failing to signal them correctly. Professionals can identify these subtler issues and ensure your system is calibrated for efficiency and safety.

Preventive Tips to Keep Auxiliary Heat Working

To prevent problems before they start, regular maintenance is key. Here are a few practical habits to keep your heat pump and auxiliary heat in top condition:

1. Change air filters monthly during peak heating and cooling seasons.
2. Schedule professional inspections at least once a year to test all heating components.
3. Keep vents clear of furniture or drapes to promote good airflow.
4. Monitor thermostat readings—inconsistent temperatures may hint at heat strip problems.
5. Clean coils and ducts periodically to prevent dust buildup from straining the system.

These steps help your system run more efficiently and extend the lifespan of critical parts like the heat strips.

The Bottom Line: A Little Warmth Goes a Long Way

A heat pump that’s not heating enough can be frustrating, especially during the coldest months. Often, the problem isn’t with the pump itself but with the auxiliary heat strips that support it when temperatures plummet.

By understanding how auxiliary heat works and learning to identify potential problems early, you can keep your home comfortable without unnecessary energy waste or repair costs. And if you’re ever unsure, don’t hesitate to bring in a qualified technician—sometimes the best fix is a professional touch.

Conclusion

Your heat pump and auxiliary heating system work hand in hand to maintain comfort, efficiency, and reliability throughout winter. A little knowledge about how these components interact can save time, money, and frustration when the chill sets in.

By checking thermostat settings, inspecting components safely, and scheduling routine maintenance, you can ensure your auxiliary heat strips remain ready to step up when your home needs that extra boost of warmth.

When your heat pump feels like it’s not quite keeping up, remember: the solution might be as simple as giving your auxiliary heat a little attention.