Heat Pump Frozen or Iced Over? What's Normal vs. What Needs Repair

If your heat pump's outdoor unit is covered in frost or ice, don't panic. Light frost is completely normal during heating mode, and your system has a built-in defrost cycle to handle it. The problem is knowing when normal frost crosses into "call for service" territory. This guide helps you tell the difference and shows what to do if your heat pump won't defrost or needs professional heating repair.

Normal Ice vs. Problem Ice: Quick Assessment

Use this table to identify what you're seeing and whether it needs immediate attention.

In North Texas, you'll see more frost during humid mornings in the 30-40°F range. This is when your heat pump works hardest, and defrost cycles run every 30-90 minutes. That's completely normal.

What NOT to Do

Before we get into repair causes, here's what you should never do when you see ice on your heat pump:

• Never pour water on the ice. Hot water causes thermal shock that cracks components and damages electronics. Cold water just adds more ice.
• Never chip or scrape ice off. You'll damage the delicate coil fins (expensive to replace) and can bend fan blades or puncture refrigerant lines.
• Never use a heat gun or torch. You'll melt plastic parts, damage wiring, and create a fire hazard.

If ice is severe, switch your thermostat to "emergency heat" mode. This stops the outdoor unit and runs backup heat inside while you wait for service.

Causes That Need Service

Defrost Control Failure

Your heat pump has a control board, sensor, or timer that triggers defrost cycles. When this component fails, the system doesn't know when to defrost. Ice continues building because there's nothing telling the unit to reverse and melt it off. You'll see thick ice that never clears, even after the unit runs for hours.

Cost to fix: $150-400 for sensor replacement, $300-600 for control board.

Low Refrigerant from a Leak

When refrigerant levels drop due to a leak, the outdoor coil runs too cold. This causes excessive frost formation that the defrost cycle can't keep up with. You'll often see ice on the refrigerant lines (copper pipes) in addition to the coils. Low refrigerant also reduces heating capacity, so your home won't warm up properly.

An EPA-certified technician must find the leak, repair it, and recharge the system.

Cost to fix: $500-1,500 depending on leak location and refrigerant type.

Reversing Valve Malfunction

The reversing valve is what allows your heat pump to switch between heating and cooling modes. During defrost, the system needs to temporarily reverse to cooling mode to send hot refrigerant to the outdoor coil. If the valve sticks or fails, the unit can't defrost. Ice builds continuously because the heat pump stays locked in heating mode.

You might hear unusual hissing or clicking sounds when the system tries to defrost but can't complete the cycle.

Cost to fix: $400-800 for reversing valve replacement.

Outdoor Fan Motor Failure

The outdoor fan moves air across the coil during both heating and defrost cycles. When the motor weakens or fails, there's not enough airflow to dissipate ice during defrost. You'll notice the fan running slowly, making strange noises, or not running at all while ice continues to accumulate.

This is a common issue in systems that are 10+ years old or units exposed to extreme weather.

Cost to fix: $300-600 for fan motor replacement.

Dirty or Blocked Outdoor Coil

When your outdoor coil gets clogged with dirt, cottonwood seeds (common in North Texas springs), or debris, airflow restriction causes ice to form faster than defrost cycles can clear it. The coil fins get packed with material, and the system can't exchange heat properly.

Cost to fix: $100-200 for coil cleaning.

When to Call for Service

Contact Dallas Heating and Air Conditioning if you see:

• Ice that doesn't clear after 2 hours
• The entire unit encased in solid ice
• Ice returning immediately after defrost cycles
• Ice on refrigerant lines or inside your home
• Your heat pump not producing heat

Our EPA-certified technicians have 20+ years of experience diagnosing heat pump issues in Dallas and the north suburbs. We understand how North Texas humidity and temperature swings affect defrost cycles, and we'll get your system running efficiently again.

Call (214) 710-2515 for same-day service on frozen heat pump repairs.