Where is the fuse that controls the AC?

In most cases, the fuse or protective device for the air conditioning system is either a circuit breaker in the home’s main panel or a dedicated disconnect near the outdoor unit; in a car, the A/C fuse or relay is typically found in the engine bay or interior fuse box. This article explains where to look for these protections and how to verify them.

The phrase “fuse that controls the AC” can refer to different protections depending on the system. For a home central air conditioner, protection can be provided at the main service panel (a breaker) and, for the outdoor condenser, at a local disconnect box that may hold fuses. Some indoor units (furnace/air handler) also contain a fuse protecting the 24-volt control circuit. In vehicles, the A/C compressor is controlled by a fuse and often a separate relay located in the engine bay fuse box or the interior fuse box. Knowing these locations helps diagnose a non-working system safely.

Home Central Air Conditioning: Fuse/Breaker Locations

Check these common spots first when a central air conditioner won’t run or trips a breaker.

• Main electrical panel: Look for a circuit breaker labeled HVAC, A/C, outdoor unit, COND, or something similar. The breaker is typically 20A or 30A, depending on the installation.


• Outdoor disconnect box: Mounted near the outdoor condenser, this weatherproof disconnect may contain fuses (often two) or simply a switch. If there are fuses, they are usually 20A each, but ratings vary by system.


• Furnace or air handler control panel: Some systems include a small fuse protecting the 24V control circuit inside the indoor unit. If present, it will be shown on the unit’s wiring diagram or inside the service panel.


• Other protective devices: In older or apartment setups, there may be an additional dedicated disconnect or a separate fuse in a nearby enclosure. Always consult the system’s label or manual for exact protection points.

If a fuse has blown or a breaker has tripped, reset or replace it with a device of the same rating. If problems recur, contact a licensed HVAC technician to diagnose underlying causes such as electrical faults or refrigerant issues.

Safety and Next Steps

Always turn off power to the affected unit before inspecting electrical components. If you’re unsure about handling electrical panels or disconnect boxes, seek professional help to avoid shock or fire risk.

Automotive Air Conditioning: Fuse Locations

Cars protect the A/C circuit with fuses and relays located in the engine bay fuse box and, in some models, a secondary fuse box inside the vehicle. The exact locations are model-specific, so consult the owner’s manual or the fuse diagram on the fuse box cover.

• Engine bay fuse box: This is the most common location. Look for fuses labeled A/C, AC, HVAC, or compressor, and note the corresponding relay for the clutch. Fuses are typically 10A, 15A, or 20A, depending on the vehicle.


• Interior fuse box: Some cars place an A/C fuse or the A/C relay in the passenger-side or driver-side interior fuse box. Check the diagram for labels related to air conditioning.


• Relays: The A/C compressor clutch relay is often separate from the fuse and can be located in either the engine bay or interior fuse box. A faulty relay can prevent the compressor from engaging even if the fuse is intact.


• Diagrams and manuals: Always verify with the vehicle’s diagram, as fuse ratings and locations vary widely by make, model, and year.

If the A/C fuse blows repeatedly or the relay fails to click, there may be an electrical short, a faulty compressor, or wiring between the relay and the compressor clutch. Replace fuses only with identical ratings and replace faulty relays as needed; persistent issues require a professional automotive technician.

Summary

Locating the fuse that controls the AC depends on the system: for homes, start at the main panel and the outdoor disconnect box, and check indoor service panels if present; for cars, inspect the engine bay fuse box and, if applicable, the interior fuse box for A/C fuses or the A/C relay. Always use the correct fuse rating, follow safety precautions, and consult a professional if the problem persists after checking these common protection points.

Which fuse controls air conditioning?

TR”
Typically, AC systems use “TR”-type fuses to ensure safe system operation.

How do you reset the fuse on an air conditioner?

If you have fuses, you can only reset the AC by taking the fuse out. After the 30 minutes lapses, reinstall the fuse back in position if it's still in good condition, but replace a worn-out fuse with a new one. Now turn the AC back on, confirm if the thermostat is set to cool, and observe how the unit functions.

How to locate an AC fuse?

Has our control board and our main furnace blower. Now you'll see right here on this control board there's a little fuse. And right there it says three on the end of it which means it's a 3 amp fuse.

How do you know if your AC fuse is blown?

You can tell if an AC fuse is blown by checking if the air conditioner won't turn on, if warm air is blowing from the vents despite the fan running, or by visually inspecting the fuse for signs of damage like a black or cloudy appearance. If you can't tell visually, use a multimeter to test the fuse for continuity; a lack of continuity indicates it's blown. 
Signs that suggest a blown fuse 
This video shows how to check if an AC fuse is blown by visually inspecting it: 58sgrayfurnacemanYouTube · May 13, 2012

• No power at all: The unit is completely silent and the thermostat may show no display, indicating the system is not receiving power at all. 
• Warm air from vents: The fan is running, but the air is not cool. This can happen if the fuse for the compressor has blown while the fan's fuse is still good. 
• Visible damage: If you can safely access the fuse (often in a disconnect box near the outdoor unit), look for a fuse that is blackened, cloudy, or has a broken filament inside. 
• Burning smell: A sharp, burnt smell near the unit can indicate a blown fuse or other electrical damage. Shut the system off immediately and call a professional. 

How to test a fuse
Note: Always turn off power to the unit at the breaker before inspecting fuses. If you are uncomfortable with any of these steps, call a professional technician. 
This video shows how to test an AC fuse with a multimeter: 57sVanport Mechanical & Fire Sprinkler Inc.YouTube · Jul 2, 2020

1. Turn off the power: Shut off the power to the AC unit at the main circuit breaker. 
2. Locate the fuse: Find the fuse box or disconnect block near the outdoor unit. It often contains one or two cartridge-style fuses. 
3. Remove the fuse: Carefully pull the fuse out of its holder. 
4. Test with a multimeter: 
   • Set your multimeter to the continuity or resistance (ohms) setting. 
   • Touch the probes to each end of the fuse. 
   • If the multimeter reads continuity (e.g., a beep or a low resistance reading), the fuse is good. 
   • If the multimeter shows no continuity (e.g., it beeps, says "OL," or displays an open circuit), the fuse is blown. 

What to do if the fuse is blown

• Replace it correctly: If the fuse is blown, replace it with a new one of the exact same type and amperage rating. Never use a fuse with a higher amperage, as this can be a fire hazard. 
• If it blows again: If the new fuse blows again immediately, there is likely another electrical problem in the system, and you should call a professional for diagnosis.