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Why A/C Keeps Blowing Fuse in Circuit Board (How to Fix)

air conditioner blowing fuse

An A/C that is blowing the fuse in the circuit board means that there is a fault with the electrical circuits, or the cooling system.

One of the most inconvenient and common problems with cooling systems is the AC that blows a fuse in the electrical control box during cycling or a breaker that trips often. Having to replace the fuse frequently is a time-consuming process.

An issue in the electrical connection, the circuit that powers the system or the power supply, are the most common causes of a air conditioner tripping a breaker or blowing a fuse.

Fuses and breakers trip or blow when the voltage going through the line is too much to handle.

Understanding the root cause of the issue can help you decide if you should repair it or whether it requires assistance from a professional.

Read on to understand the reasons behind your air conditioning unit blowing a fuse in the circuit board frequently, and a few possible ways of fixing these issues.


Why Is My AC Blowing a Fuse?

The electric circuit feeding your AC and the AC unit comprises of several components. The reason behind your AC blowing a fuse could be because of the malfunction of any of these components.

Here is a list of the most common reasons that could be the cause of your AC blowing fuse.

  • Dirt and Temperature Fluctuations

Damaged motors, dirty coils and intense temperature fluctuations can put a strain on your AC’s condenser and cause it to breakdown. This, in turn, causes the electric circuit to be overloaded and the fuse to blow up.

Repair damaged motors immediately, clean dirty coils and set right temperature fluctuations.


  • Deterioration of the Fuse

A fuse lasts for approximately 20 years. It also depends on how often the AC is used. Fuses installed in the AC are time-delay fuses and work when the machine is turned ON or OFF.

The fuse wires will be subject to wear and tear due to the constant use of the AC unit. These should be checked regularly and worn or frayed fuse wires should be replaced immediately.


  • Old or Clogged Motor

The AC’s capacitor needs to exert extra effort in case the motor is clogged or worn out. A condenser is responsible for the running of the cooling system.

The role of the capacitor is to help the condenser. It helps in regulating the current flowing through the condenser.  Therefore, if the capacitor is not working properly, it will blow the fuse in no time.


  • Unsteady Electrical Connection

Another reason could be unsteady connections within the breaker box due to extreme temperature changes. Temperature fluctuations can lead to sudden expansion and contraction of fuses, which makes them loose and unsteady. Get the unit inspected by a qualified service technician to set right this problem.


  • Loose electricity cables 

A short circuit could be caused by loose electrical cables within the circuit box or anywhere in the air conditioner. It is important to get these checked and tightened by a trained technician to prevent short circuits.


Why Your Air Conditioner Keeps Blowing Fuse in Circuit Board


  • Decreased Refrigerant Level 

Decreased refrigerant level causes strain in the AC as it struggles to reach the set cooling levels of your home. The additional work that the AC has to execute can blow the fuse or trip the circuit breaker. Ensure that the refrigerant level is always maintained correctly.


  • Undersized Fuse 

If your AC’s circuit board has a fuse with inadequate capacity, then it will fail to stand the load of the AC causing it to blow fuse frequently until it is changed to one of the right specs.


How do I stop my air conditioner from blowing fuse?

Here are some steps you can follow to ensure that your air conditioner does not trip the circuit breaker or blow fuse frequently.


  • Ensure your air filter is clean

Homeowners often ignore to check their air filter, which could be the source of many problems in their AC.

Dirt and dust can clog the filter and restrict the airflow, which will force the unit to struggle. To avoid this, it is recommended to check your AC’s air filter every three months. In case the air filter is dirty, get it cleaned immediately.


  • Ensure your outdoor unit is clean

Just like the air filter, it’s essential to ensure that the surroundings of your air filter are clean and free from outside dirt, grass clippings and dried leaves. For this, you may use a firm brush or an old screwdriver to dislodge the debris.

Make sure that the vents are not being blocked by any furniture, window curtains or the carpet.


  • Reset the breaker

Another important quick fix is to reset the breaker. In case you have an old electrical system, you can also swap the fuse.


How to replace a blown Air Conditioner Fuse

When the fuse blows out you might hear a faint humming sound from the outside equipment which is harmless.

It is important to ensure that the problem is caused by a blown fuse, which can be done with the help of a voltmeter. A zero-volt reading confirms a blown fuse. If the voltmeter shows a reading, the problem could lie elsewhere.  Here is how you can safely replace a blown fuse.


Step 1 – Identify the fuse

Before you dismantle the parts of your air conditioner to replace the fuse, it is important to find out the fuse and its type.

It is imperative to turn off your air conditioning unit’s electricity source before you open the unit’s compartment.

Look for a switch close to the compressor. The circuit breaker that controls the air conditioner should also be turned off. Finally, turn off the switch in your unit.


Step 2 – Check the electric circuit

When you open the compartment door near the compressor’s switch, you will find two cartridge fuses. There are wires connected to both ends of the fuses. Take the voltage tester and test the two wires emerging from the disconnect switch.

The disconnect switch is placed on the top of the fuses.

Take your voltage tester and test both the terminals, as well as the wires at the bottom. You must only proceed if no voltage is registered after testing the wires.


Step 3 – Remove the fuses

You may use a fuse puller to take the fuses out. Note the amperage mentioned on each. Usually, there is a 30-amp label on the fuses. However, verify the kind of fuses, namely- fast, standard or delay-rated. Buy a pair of fuses that are like the ones that were taken out.


Step 4 – Test out the new fuses

When you buy a new fuse, ensure that you check them thoroughly for consistency. Good quality fuses help your air conditioning unit to work properly. Quite often, there is a need to replace only one of the fuses. However, to ensure that the AC unit works smoothly, it is recommended to replace both the fuses.


Step 5 – Insert the new fuses

Use the fuse puller to install the new fuses. It is extremely important to make sure that the fuses are rightly placed in their respective clamps. Note that if the wires of the clamps are not correctly positioned on the fuse terminals, the air conditioner will still not work.


Step 6 – Finally, test your air conditioner

After confirming that the fuse has been placed correctly and all other connections are proper, turn the circuit breaker and thermostat on. Turn on the power and switch ON the AC. If it works properly, you have successfully repaired it!


3-Amp fuse keeps blowing on AC

Here are some reasons why the3 Amp fuse keeps blowing up on your air conditioner:


  • Fault in the contactor

If you have a low voltage fuse and power is coming off a 24-volt transformer, the contactor in your condensing unit may have shorted out causing it to blow the fuse.


  • Thermostat wire nicked

If you have a rodent problem in your area, they could have bitten through the wires. Another reason could be a weed whacker that might have cut the thermostat wire to the condenser and caused the unit to trip while cooling.


  • Disconnect everything

Turn the power switch OFF and disconnect everything. Start turning on the switches in order, one after the other. If the fuse blows out again, note at what stage the fuse blew out.

Look for any wire rub-outs, cracked wire insulations or a bad connection in this area. Fix the problems that you have come across and test your unit again.


5-Amp fuse keeps blowing on AC

  • Disconnect the compressor contactor
  • Once you disconnect the compressor contactor, set thermostats to cooling mode and tape off the low voltage wire to restart. You may also cut off the REV valve low-voltage wire.

If the 5-Amp fuse keeps blowing, the probable reason could be in the thermostat or the defrost board. You must remove the thermostat and hard wire at the wall, which will help you establish the location of the short.

Once you locate the problem, rewire the control back into the circuit and retest after fixing the part that caused the fuse to blow.

Ernie Lo

Ernie Lo is a qualified web designer and web developer. He works as an IT support technician and website manager at Benleigh Vending, and he also fixes vending machines.

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