There is a specific kind of frustration that comes with a heat pump that almost works. The thermostat says 70. The house says 66. The outdoor unit has been humming since breakfast. Nothing is broken enough to call it broken, and nothing is working well enough to call it fine.
That gap between setpoint and actual is a capacity problem, and capacity problems have a short list of causes. Here is how we work through them on service calls in Federal Way, Kent, Puyallup, Tacoma and Olympia — starting with the checks that cost nothing.
First, confirm it is actually a capacity problem
Two situations look identical from the hallway and are completely different underneath.
- The system runs constantly and the house slowly gains, just not fast enough. That is a capacity shortfall. Keep reading.
- The system runs constantly and the house loses ground. Same list of causes, further along. Treat it as urgent during a cold snap.
- The system cycles on and off and still misses the setpoint. That is a control or sensor issue, not capacity, and it points at the thermostat, wiring, or defrost board.
Also check what the thermostat is set to. A programmed setback that recovers slowly is not a fault — a heat pump recovering from a 62-degree setback can take two to three hours to climb back to 70, because it is designed to deliver low, steady output rather than a furnace's short hot blast. If the house only misses the mark after a scheduled setback, flatten the schedule before you call anyone.
The free checks, in order
1. The filter
This is not a throwaway line. A clogged filter is the single most common reason a heat pump underperforms in this region, and crawl-space air handlers make it easy to forget for two years at a stretch. Restricted airflow drops the amount of heat the system can move into the house even when the equipment itself is perfectly healthy. Pull it. If light does not pass through it, replace it and give the house four hours.
2. Registers and returns
Closed vents in unused rooms, a rug over a floor register, furniture against the return grille. Every blocked opening raises static pressure and lowers delivered capacity. Open everything.
3. The outdoor unit
Walk out and look at it. In Puget Sound the usual offenders are fir needles packed into the coil fins, blackberry growth, a tarp someone threw over it in October, or leaves banked against the base after a wind storm. The outdoor coil is how the system pulls heat out of the air. If it cannot breathe, it cannot heat.
4. Thermostat mode
Make sure it is on HEAT, not EM HEAT or AUX only, and that the fan is on AUTO. If none of that applies and the system is simply not responding, our guide to a heat pump that isn't heating covers the breaker and control checks in more detail.
The real causes, and what each one costs to fix
If the free checks pass and the house still will not get there, it is time for a heat pump repair diagnostic. Here is what we actually find.
Low refrigerant from a leak
Refrigerant is not consumed. If the charge is low, it leaked. A system running 15 or 20 percent undercharged still runs, still blows air that feels vaguely warm, and still cannot produce enough heat to close a four-degree gap. This is the number one cause of the almost-works complaint. The fix is finding and sealing the leak, then recharging — topping off a leaking system is paying for refrigerant that will be in the atmosphere by spring.
A dirty indoor or outdoor coil
Coils collect what the air carries. Indoor coils glaze over with dust that slipped past a cheap filter. Outdoor coils in Des Moines, Burien, Steilacoom and Gig Harbor get salt-air corrosion on top of ordinary grime. Either one acts like insulation on the exact surface that is supposed to transfer heat. Cleaning is maintenance pricing, not repair pricing.
Duct leakage and undersized returns
The equipment can be perfect and still fail if a third of the heated air is dumping into a vented crawl space. Puget Sound crawl spaces and attics are damp, and old flex duct pulls apart at the collars. We see homes losing real capacity to disconnected branches nobody has looked at in 20 years. A duct inspection is part of every estimate, and targeted repairs are often far cheaper than new equipment.
A failing defrost cycle
In winter the outdoor coil frosts, and the system periodically reverses to melt it. That is normal, including the steam. What is not normal is a defrost board or sensor that leaves the unit iced over for hours, or that triggers defrost constantly and spends half the day not heating. Either way the house never catches up.
A weak blower or failing capacitor
A blower motor that has slowed with age moves less air through the same ducts. A weak capacitor lets the compressor or fan start but not perform. Both produce partial heat rather than no heat, which is exactly why this symptom confuses people.
Backup heat that never engages
Most ducted heat pumps here include electric backup strips for the coldest hours. If the strips, their sequencer, or the thermostat staging has failed, the system loses its last 20 percent of capacity on the coldest mornings — the only days you would notice.
Equipment that is simply too small
Sometimes nothing is broken. A 2.5-ton system on a house that needs 4 tons will run nonstop all winter and never hit the setpoint on a cold morning, right out of the box. Olympia, Lacey and Tumwater homes are designed against a 17°F winter design temperature, while Tacoma and Gig Harbor sit at 29°F — a twelve-degree spread across our service area that a lazy sizing job ignores. The only honest fix is a real Manual J load calculation and correctly sized equipment.
Repair or replace
| Situation | Typical cost, standard markets |
|---|---|
| SituationFilter, cleaning, sensor, capacitor | Typical cost, standard markets$150 – $600 |
| SituationRefrigerant leak repair, blower motor, defrost board | Typical cost, standard markets$600 – $1,500 |
| SituationHeat pump replacement on existing ducts | Typical cost, standard markets$10,000 – $16,000 |
| SituationNew ducted heat pump system | Typical cost, standard markets$12,000 – $18,000 |
Affluent and luxury markets run higher — repairs to $1,800 and $2,000, replacement to $19,200 and $21,600. Our Washington heat pump cost guide breaks down every line.
The rule we use: if the system is under about 15 years old and the repair costs less than half of replacement, repair it. Most of the causes above are well under that line. Where replacement earns its keep is a compressor failure, a coil that leaks again after being sealed, or equipment that was never the right size for the house.
One more thing about cold weather
Western Washington is one of the best heat pump climates in the country, and a correctly sized modern system holds setpoint here through a normal winter without breaking a sweat. If someone tells you the house is cold because heat pumps just do not work when it gets chilly, that is a sales line. We wrote the long version in do heat pumps work in Washington winters. Short version: yes, and a system that cannot reach setpoint at 30°F has a fault worth finding.
What happens when you call us
A technician diagnoses the problem and gives you a price before any work starts. Same-week scheduling, Monday through Friday, 8 to 6. If the fix is a $300 part, we say so — several of our reviews exist precisely because we talked someone out of a new system.
If replacement genuinely is the right call, every Varsity install carries a 10-year parts and labor warranty, most are finished in one day, and local utility rebates may apply. The amount depends on what is being replaced and the equipment installed, and programs change, so we read the utility off your bill, confirm what it currently pays, and file the paperwork.
Call (253) 785-4622 or request an estimate and we will find out why your house is four degrees short.