If a heat pump will not start, safe checks can include thermostat settings and obvious power and control status. Repeated breaker trips, burning smells, or electrical abnormalities should not be repeatedly reset or investigated as DIY work — they need a licensed technician.
A heat pump that will not turn on at all — no fan, no compressor, no response — typically has a cause related to power supply, thermostat, or controls. The most common non-emergency causes are a thermostat with dead batteries or lost settings, a tripped circuit breaker, or a disconnect switch that is in the off position.
Safe checks any homeowner can perform: verify thermostat operation, check the outdoor disconnect switch, and look for a tripped breaker in the electrical panel. If none of these resolve the issue, or if there is a burning smell, sparking, or the breaker trips again immediately after reset, stop and call a licensed technician.
Do not attempt to open electrical panels, inspect wiring, or repeatedly reset a breaker that keeps tripping. These actions can cause injury and damage equipment rather than resolve the underlying fault.
Work through these in order. Each check is safe to perform without tools or technical knowledge. Stop at any point where the check reveals a problem that needs professional attention.
Is the thermostat screen on and showing a reading? A blank or dark display can mean the thermostat has lost power. If it uses batteries, replace them and see if the display comes back. Some systems have a C-wire (common wire) powering the thermostat — if it's battery-backed only, this is often the first place to check.
Confirm the thermostat is set to Heat (or Cool, depending on the season), and that the setpoint is above (for heating) or below (for cooling) the current room temperature. If the room is already at the setpoint, the system will not call for operation. Raise the setpoint a few degrees and wait 2–3 minutes.
Most heat pumps have a dedicated disconnect switch in a box mounted on the exterior wall near the outdoor unit. This switch should be in the ON position. It may have been switched off after a maintenance visit or by accident. Verify it is on, then wait a few minutes for the system to attempt a start (some systems have a built-in time delay).
Go to your main electrical panel. Look for a breaker that is in the middle "tripped" position — it will be between fully ON and fully OFF. If you find a tripped breaker labelled for the heat pump or air handler, reset it once: switch it fully to OFF then back to ON. Then observe — if the system starts and the breaker holds, monitor for the next cycle. If it trips again, stop resetting.
The indoor air handler (if you have a split system) may have its own power source — either a dedicated breaker or a power switch on or near the unit itself. Some air handlers have a power switch that looks like a light switch, mounted on the unit or on the nearby wall. Make sure it is in the on position.
If the safe checks above do not resolve the issue, these are the most common causes a technician will diagnose.
A loss of power to the heat pump — whether from a tripped breaker, a blown fuse in the disconnect, or a supply issue — will prevent any operation. A single trip may be an isolated event. Repeated trips indicate a fault in the electrical circuit, compressor, or wiring that requires diagnosis before the system can be safely operated.
A failed thermostat — blank screen, corrupted programming, dead communication board, or no signal to the heat pump — can prevent the system from receiving a call to start. Even if the display is on, the thermostat may not be communicating correctly with the outdoor unit. A technician can verify the signal the thermostat is sending.
The outdoor disconnect switch may be off following a maintenance visit, an accidental bump, or an intentional but forgotten shutdown. This is one of the simplest causes — and one of the safest for a homeowner to check — but is sometimes overlooked. Check it is firmly in the ON position.
Heat pumps have built-in protection that causes the system to lock out and stop operating if it detects a pressure condition outside of safe parameters. A lockout can be triggered by a refrigerant issue, a blocked coil, or an equipment fault. Once triggered, some systems require a manual reset by a technician before they will operate again.
An internal electrical failure — a burned control board, failed capacitor, damaged wiring harness, or compressor issue — can prevent the system from starting. These faults may or may not produce an error code on the thermostat display. A technician uses diagnostic tools to identify which component has failed and what the repair or replacement path is.
There is a burning smell coming from the air handler, outdoor unit, or any electrical panel. You can see sparking or arcing near any electrical component. There is visible smoke. The breaker trips again immediately after you reset it — this means the circuit is detecting an active fault, and resetting it further risks damage and injury.
In these situations, do not continue resetting breakers, do not attempt to open any electrical panel or access point, and do not operate the system. Call a licensed HVAC technician or electrician. Climax Energy provides heat pump diagnosis and repair across Metro Vancouver — call (250) 201-2030.
Diagnosis and repair for all heat pump makes and models across Metro Vancouver.
System starts but produces no heat? Different causes than a system that won't start at all.
Annual tune-ups to identify issues before they cause a no-start or breakdown.
When the diagnosis indicates the repair cost exceeds replacement value, we can help you choose the right new system.
If power and reset checks do not resolve the problem, request professional heat pump service — do not continue resetting breakers.
Answers to the questions we hear most often when a heat pump will not turn on.