heat pump troubleshooting
Heat pump turns on and off every few minutes
What it probably is, what you can safely check yourself, and the point where it becomes our job.
It is still running, so you have a few days. It is not going to fix itself, and the part that failed rarely fails alone.
What is most likely going on
Short cycling means the system satisfies or trips before it reaches steady operation, and that wastes the efficient part of every run while wearing the compressor. The usual causes are oversized equipment, restricted airflow, a badly located thermostat, or a repeating safety trip.
Likely causes, most common first
- 1
Equipment oversized for the actual load
A system sized off square footage rather than a load calculation at our 19°F design temperature overshoots the setpoint and shuts down. It is the most common design error we find in Whatcom County, and it is not fixable with settings; it is a sizing decision made at purchase. Inverter equipment hides it better than single-stage equipment, but it still costs you comfort.
- 2
Restricted airflow across the indoor coil
A clogged filter, a closed-off supply register, or crushed flex duct in a crawlspace starves the coil and drives the system onto a limit switch. It stops, cools down, restarts and repeats. This is the cheapest possible cause and the first one to eliminate.
- 3
Thermostat location or a very narrow differential
A thermostat above a woodstove, in direct sun from a west-facing bay window, or on an exterior wall reads a temperature the rest of the house does not have. A differential set too tight has the same effect, cutting the run before the house has actually moved. Both are correctable without touching the equipment.
- 4
A repeating pressure or temperature safety trip
High or low pressure trips from a dirty coil, low charge, or a failing fan look exactly like short cycling from inside the house. The difference is that the equipment is protecting itself rather than satisfying the thermostat, and each trip is a data point that a technician can read.
- 5
Failing capacitor or contactor
A weak run capacitor lets the compressor start and then drop out on overload, producing a stop-start pattern that mimics a control problem. It is a component-level repair, and catching it before it takes the compressor with it is the whole point of calling early.
What you can safely check yourself
Work down the list before you book anything. Plenty of calls end here, and we would rather you keep the money.
- Replace the indoor filter and open every supply register in the house, including in rooms you keep closed.
- Time the cycles and write down how many minutes it runs and how many it rests, which tells us a lot before we arrive.
- Look at where the thermostat is mounted and note any heat source, direct sun, or draft near it.
- Confirm the thermostat is not in emergency or auxiliary heat, which changes the staging behavior entirely.
- Check the breaker and the outdoor disconnect, since a marginal connection can drop the unit out under load.
What is deliberately not on that list
Nothing above involves refrigerant, gas piping, or opening a live electrical panel. Refrigerant work is federally regulated and needs recovery equipment. Gas work done wrong kills people. An energised panel turns a $300 repair into a hospital visit. Electrical work on the circuit itself is done by a licensed electrical contractor. If a step you have read elsewhere involves any of those three, stop and call instead.
When to call us
Call us if cycles stay under about ten minutes after a filter change, or if the pattern started suddenly, which points at a component rather than at sizing. Bring your cycle timings to the call. We answer at (360) 592-3824 during regular hours of Monday–Friday 8:00 AM–5:30 PM.
Monday–Friday, 8:00 AM – 5:30 PM · Emergency calls answered 24/7
Tell us what it is doing
Describe the symptom and we will tell you what it takes to fix, what it is likely to cost, and whether it is worth fixing at all.
Monday–Friday, 8:00 AM – 5:30 PM · Emergency calls answered 24/7