Answer first, context after
Why does my heat pump blow lukewarm air? Is it broken?
Probably not. A gas furnace blasts genuinely hot air, but a heat pump delivers air around 90 to 100 degrees, which heats the house fine yet feels cool against your 98.6 degree hand. If the house holds temperature, the system is working as designed. If the house is losing ground, or the air is actually cold, then it is a service call.
This is the most common phantom problem in heat pump ownership, and it peaks every winter when someone who grew up with gas heat gets their first heat pump. The register that used to blast hot air now breathes warmish air, and it feels like something failed. Usually nothing did.
The hand test is lying to you. A gas furnace delivers air hot enough to feel unmistakably toasty. A heat pump delivers air in the 90s to low 100s, warmer than your room but cooler than your skin, and anything cooler than skin registers as “cool” to a hand held in the airflow. The room is being heated the entire time. Heat pumps compensate for the gentler supply air by running longer, steadier cycles, which is not a defect either: long low runs are how they achieve their efficiency, and the even temperature they hold is one of the reasons people end up preferring them.
The actual test: ignore the hand, watch the thermostat. Set a temperature, give the system time, and see whether the house reaches and holds it. Holding setpoint means healthy. A system running constantly while the house loses ground is a real problem, and air that is genuinely cold, room temperature or below, in heating mode is a real problem too.
One more normal-but-alarming behavior: on cold mornings a heat pump periodically runs a defrost cycle, during which the outdoor unit may steam like a kettle and the indoor air may briefly go cool. Steam from the outdoor unit in winter is the machine clearing frost off itself, not smoke, and it is routine.
When it is actually broken: low refrigerant from a leak, a failing reversing valve, or backup heat quietly carrying the load and inflating the bill. The tell for that last one is an electric bill spike alongside the lukewarm complaint. Any of those earns the $89 diagnostic, waived with the repair. But if your only symptom is air that feels less dramatic than the gas furnace you grew up with, your heat pump is fine, and it is costing you less than that furnace did.
Still stuck? That's what the truck is for.
The diagnostic is $89, waived when you book the repair, with a written flat price before any work starts.