Fuses play a vital role in maintaining the overall integrity of the AC system, ensuring its safe and reliable operation while also safeguarding against potential fire hazards that could arise from electrical failures. If the AC fuse blows, your air conditioner won't turn on.
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.
The AC fuse on most HVAC systems is typically on the unit's control board. You'll normally find the board behind an access panel on the unit's lower compartment. While you sometimes have to unscrew areas to access the control board, others have clips.
Blowing the fuse cuts the power to the unit to prevent electrical damage. If your AC has shut down and won't start again, especially if you've noticed odd electrical behavior immediately before the shutdown, chances are the fuse has done its job and will need to be replaced.
Wear and Tear on the Fuse
The lifespan of a fuse can be up to 20 years. AC fuses are usually what is known as 'slo-blow' or 'time delay' fuses. This means that they are at work every time you turn the machine on and off and eventually, will simply wear out due to the strain of the operation.
It's important to be able to recognize the signs. If your device suddenly stops working, it could be a blown fuse. Check for discoloration or markings on the fuse. If you see any damage, there's a good chance the fuse needs to be replaced.
Fuses for protecting HVAC equipment are typically cylindrical cartridges that snap into fuse holders inside the manual disconnect box. They're opaque, so when one blows you may not be able to tell by looking at it. You can test for a blown fuse with a multimeter, or do as some people do and simply replace it.
In AC systems, the air conditioner reset button is on the outside unit's lower edge, typically close to the ground. Some models have the reset button located behind the service panel, which may require tools to remove. Reset buttons are usually red or yellow with a clear “reset” label.
If your AC capacitor has broken down, it may cause the air conditioner to blow fuses. You should have your capacitor tested or replaced if necessary by trustworthy AC professionals. Loose wiring is another common culprit for blown AC fuses.
Check the thermostat
You should check if it's been set to the correct temperature and also make sure it's set to “cool”. If the AC settings are not right, it won't turn on. You can also check if the batteries in the thermostat are fresh and replace them if needed.
For AC capacitor replacement, anticipate spending between $150 and $400, depending on the capacitor's type and accessibility. A bad AC capacitor is a fairly minor repair, and most HVAC technicians will recommend a repair rather than replacing the unit when the capacitor is the problem.
If you think your air conditioner has blown a fuse, the first sign you'll notice is that the outside AC unit is inoperable. The best way to check for a blown fuse is by using a voltmeter. Be warned — you are working with live electricity and should use extreme caution when troubleshooting your system.
Not all air conditioning units have a reset button, but if yours does, it's typically located on the outdoor unit. Here's how to locate it: Turn Off the Power: Before you search for the reset button, ensure the power to the unit is turned off for safety reasons.
A fuse is a glass tube with a thin piece of wire inside (also known as a ribbon) that handles a specific amount of current. The ribbon is sized to match a circuit's wire size (or gauge) and if too much current passes through the ribbon, it will melt, or blow.
Look at the fuse wire. If there is a visible gap in the wire or a dark or metallic smear inside the glass then the fuse is blown and needs to be replaced. If you cannot see whether the fuse is blown, follow steps 4 and 5.
The blown fuse will be apparent because the wire element within will have melted or burned from the higher electrical current. You can also leverage diagnostic tools like a test light or a multimeter to identify the dead fuse without having to pull it out. Both devices are affordable and easy to use.
Because the fuse has blown, the air conditioner is protected. If your AC fuse is blown, it's most likely that your air conditioner will stop functioning entirely. Or, it will keep the blower running, but every other component will stop working. Of course, there could be other problems that make your AC stop working.
A fuse replacement can cost between $75 and $300. These are similar to car fuses and can blow if they get overloaded. The good news is that this type of repair is quick and not likely to rack up excessive labor fees. A relay turns on an AC unit's outdoor condenser unit.
With general wear and tear, breakers can go bad over time, too. You'll know your circuit breaker is bad if you notice these signs: Circuit breaker is hot to the touch. Burning odor around the breaker.