Direct answer: If a squirrel chewed an AC wire, turn the AC off at the thermostat and shut off power to the outdoor unit before touching anything nearby. Chewed insulation can leave live conductors exposed, short the unit, or damage low-voltage control wiring, and this is usually not a safe guess-and-patch DIY repair.
Most likely: Most often, the damage is on the outdoor condenser wiring where squirrels can reach it easily: the whip feeding line voltage, the low-voltage thermostat cable, or insulation around wires near the disconnect and cabinet entry.
Start by separating two lookalikes: visible chewing on the outdoor AC wiring versus a no-cooling problem with no visible wire damage. If you can actually see chewed insulation, exposed copper, melted spots, or arc marks, treat it as an unsafe wiring condition first and a cooling problem second. Reality check: even a small tooth mark can be enough to create a short or intermittent fault once the unit vibrates and gets wet. Common wrong move: resetting the breaker over and over to 'see if it holds.'
Don’t start with: Do not start by taping over the bite marks and turning the system back on. That hides damage, misses nicked conductors, and can turn a nuisance problem into a burned wire or failed equipment problem.
The insulation is nicked, shredded, or missing on one or more wires near the condenser, disconnect, or line set area.
Start here: Shut off the thermostat and outdoor unit power first, then inspect from a safe distance without moving the wire.
You heard or saw squirrels near the unit, and now the condenser will not start, the breaker tripped, or the thermostat calls for cooling with no outdoor response.
Start here: Check whether the breaker tripped or the disconnect is off, but do not re-energize a visibly damaged wire.
There is a sharp electrical smell, soot, melted insulation, or a pop when the AC tried to start.
Start here: Leave the system off immediately and treat it as an urgent unsafe condition.
The thin low-voltage cable jacket is damaged, but the heavier power wiring looks intact and the unit may be partly responsive or completely dead.
Start here: Still shut power off before inspection, because low-voltage damage often sits right next to line-voltage wiring and cabinet edges.
This is common because the small cable is easy for squirrels to bite, and damage here can keep the contactor from pulling in so the outdoor unit never starts.
Quick check: With power off, look for damage to the small multi-conductor cable entering the condenser cabinet or running along the line set.
If the breaker tripped, insulation is badly torn, or you see heavier black wires damaged, the squirrel may have reached the power feed rather than just the control wire.
Quick check: From a safe distance, look for torn conduit, exposed copper, melted insulation, or arc marks near the disconnect and where wiring enters the unit.
A wire can look only lightly chewed at first, then fail once moisture gets in or the unit shakes during startup.
Quick check: Think about timing: if the AC worked briefly after the chewing and then failed during rain or the next cooling call, hidden conductor damage is likely.
A hard short can take out a fuse, contactor coil, or other control component, so the visible chew marks may not be the only problem left.
Quick check: If wiring damage is obvious and the system still will not run after professional wire repair, the fault may have traveled into AC controls.
Animal-damaged AC wiring can be live even when the unit is not running. Your first job is to stop the equipment from trying to start and keep people away from the damaged area.
Next move: The unit is de-energized and you can do a careful visual check without the system trying to start. If you cannot clearly shut power off, or the breaker panel labeling is unclear, stop and call for service rather than guessing.
What to conclude: You have stabilized the hazard first, which matters more than figuring out whether the AC itself is still healthy.
You want to separate low-voltage control wire damage from line-voltage power wire damage early. They can look similar from a few feet away, but the risk level and likely repair path are different.
Next move: You can tell whether the damage appears limited to the small control cable or involves heavier power wiring too. If the damage disappears into conduit, wall cavities, or the unit cabinet where you cannot see it clearly, assume the repair needs a pro inspection of the full run.
What to conclude: Visible damage to only the small control cable often explains a dead outdoor unit, but any damage to heavier wiring or any sign of heat raises this into a strict pro repair.
A tripped breaker, dead condenser, or indoor blower running by itself helps confirm whether the squirrel damage likely opened the control circuit or caused a harder short.
Next move: You have enough symptom detail to describe the failure clearly when you call for repair, which speeds up the visit and reduces guesswork. If symptoms are inconsistent, intermittent, or you are not sure what powered down and what did not, keep the system off and avoid more testing.
Most squirrel-chewed AC wiring lands on the pro side because the damaged section is outdoors, near line voltage, and often tied to HVAC controls. The goal here is to avoid turning a visible wire repair into a hidden equipment failure.
Next move: You have a clear next action instead of guessing with tape, wire nuts, or repeated resets. If you are still tempted to patch and test, treat that as a sign to stop. This is one of those repairs that gets expensive when the first fix is sloppy.
The safe finish here is not a temporary restart. It is a proper repair, insulation integrity check, and confirmation that the AC starts and runs without tripping, overheating, or losing control voltage.
A good result: The AC runs normally again without exposed wiring, nuisance trips, or signs of heat damage.
If not: If the repaired wiring is sound but the unit still will not start or trips again, the original short may have damaged AC controls and the technician should continue with equipment diagnosis.
What to conclude: You are finished only when the wiring is repaired properly and the system proves it can start and cool normally under load.
No. Tape may cover the damage, but it does not prove the conductor underneath is intact or that the termination did not loosen or arc. On AC wiring, especially outdoors, that is not a reliable or safe final repair.
It is less hazardous than damaged line-voltage wiring, but it still should not be ignored. The low-voltage cable often runs right next to higher-voltage wiring, and the damaged section can short, corrode, or fail again if it is not repaired properly.
The chewing may have opened the low-voltage control circuit so the outdoor unit never gets the signal to start, or it may have shorted the power wiring and tripped the breaker. In harder faults, it can also damage control components inside the unit.
Not if the damage is still visible and unrepaired. Resetting the breaker can re-energize exposed conductors and make the fault worse. Leave it off until the wiring is repaired and inspected.
Either may be appropriate depending on where the damage is. If the damage is on the condenser whip, disconnect, or branch wiring, an electrician is often the right call. If it involves the thermostat cable, condenser controls, or possible equipment damage, an HVAC technician is usually the better first stop. When in doubt, describe the exact location and symptoms when you book the call.