Why Does My Heat Pump Make a Repeated Clicking Sound Right Before It Starts?
A clicking sound is heard right before the heat pump actually starts up, a sound that seems harmless most of the time but, in some cases, repeats in a loop without the unit ever managing to start.
Why one or two clicks are generally normal
The electrical relay that activates the compressor produces an audible click at the moment of engagement, a normal mechanical sound accompanying most systems' startup. A single click followed by the unit's normal startup generally poses no problem.
When repeated clicking signals a real problem
| Sign | What it indicates |
|---|---|
| One or two clicks followed by normal startup | Normal operation of the starting relay |
| Repeated clicking in a loop with the unit never starting | Failing start capacitor, unable to deliver the needed jolt |
| Click accompanied by a burning smell | A more serious electrical issue requiring an immediate shutdown |
| Clicks becoming more frequent over the weeks | A component gradually deteriorating toward complete failure |
The role of the start capacitor
The start capacitor supplies the electrical jolt needed to launch the compressor motor; a weakened or failing capacitor can try and fail repeatedly, producing the characteristic click of the relay retrying without success. This component naturally wears out over time and is a relatively standard replacement part.
Why this symptom shouldn't be ignored
A system repeatedly trying and failing to start puts the compressor under repeated stress, which can eventually damage this far more expensive component than the capacitor itself. A capacitor problem caught early generally avoids a costlier repair later.
What to do if the repeated clicking occurs
Turn the system off at the thermostat to avoid repeated startup attempts straining the compressor, and contact a technician for a diagnosis — replacing a failing capacitor is generally a quick, affordable repair once the cause is confirmed.
Frequently asked questions
How much does replacing a start capacitor cost?+
Generally one of the more affordable heat pump repairs, particularly compared to the cost of a compressor damaged by repeated failed attempts.
Can I keep using the system while the clicking happens?+
It's better to shut off the system as soon as the repeated clicking is noticed, rather than continuing to strain the compressor with failed startup attempts.
Does the capacitor wear out faster under certain conditions?+
Yes, frequent startup cycles and extreme temperatures can accelerate this component's normal wear over time.
Does a single click at startup mean everything's fine long term?+
Generally yes for the present moment, but regular maintenance helps catch a weakening capacitor before it causes a complete startup failure.
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By Marc Tremblay — Certified HVAC technician, 12 years of experience in Quebec
Updated on July 22, 2026