Why My AC Fuse Keeps Blowing In My Car [8 Ways To Solve!]

A blown AC fuse can result from a faulty AC pressure switch and damaged wires. Other reasons include broken compressor clutch, low refrigerant levels, bad field coils, overheating, or dirty HVAC filters. Maintenance may be required to restore function, including fixing, cleaning, and replacing components.

Now, let’s jump into a quick overview of the most common reasons why your Ac fuse keeps blowing. Refer to the below table for the reasons, their symptoms, and solutions.

AC Fuse Blows When Turned On – 8 Reasons And Solutions

Reasons	Symptoms	Solutions
Dirty HVAC Filter	Dust In The Cabin	Clean The Filter
Faulty AC Pressure Switch	High AC Pressure	Replace The AC Pressure Switch
Low Refrigerant Levels	Hissing Sound Near The AC Compressor	Repair With Leak Sealants
Damaged Wire Harness	Short Circuits	Replace The Wires
Malfunctioning Field Coil	Electric Motor Current Surging	Replace The Field Coil
Disengaged Compressor Clutch And Clutch Coil	AC Not Working Properly	Replace The Compressor Clutch
Overheating	Loss Of Cold Air From The Air Vents	Flush The Cooling System And Clean The Radiator
Faulty Cooling System Capacitor	Fluctuations In Electric Current	Replace The Capacitor

Knowing how to troubleshoot and fix an AC Fuse that blows when turned on can be a valuable skill to have. This can help you work better with repairmen to save some costs. 

Reason 1: Dirty HVAC Filter

An excessively dirty or blocked HVAC filter can cause the car’s AC fuse to blow. When the filter is too clogged, the air cannot pass through freely, requiring the system to draw excessive power. 

The dirty filter can also cause the evaporator coils to freeze, leading the system to draw too much power and blow a fuse.

Symptom: Dust In The Cabin

Dust particles can accumulate on the components of the system, such as the blower motor or the fan. 

Solution: Clean The Filter

Step 1: First, remove the HVAC filter from the AC unit. 

Step 2: Then, gently suck up any debris accumulated on the filter using a vacuum cleaner. 

Step 3: If the filter is filthy, you may need a mild detergent and a soft brush to scrub it. 

Step 4: Once the filter is clean, allow it to dry completely before reinstalling it. 

Doing this will help ensure that the car’s AC fuse doesn’t blow. You may not need expert hands for this; if you are confident, you can do this by yourself. 

Reason 2: Faulty AC Pressure Switch

An AC pressure switch is a safety device that monitors the refrigerant pressure in an air conditioning system. It is designed to protect the compressor from damage due to low or high refrigerant pressures.

If the pressure switch detects a problem with the refrigerant pressure, it can trigger the AC system to shut down or prevent it from turning on altogether.

If the pressure switch fails and does not detect a problem with the refrigerant pressure, it can cause the AC compressor to continue running, which can result in overheating and eventually blow the AC fuse

This situation could result in the frequent fusing of the AC fuse due to an excessive pressure buildup within the system. 

Symptom: High AC Pressure

Symptoms of malfunction may encompass a reduction in air conditioning efficiency. For instance, longer cooling time or abnormally high pressure in the AC unit. There are a few signs that can indicate high pressure in an AC unit:

1. The AC system may not cool as effectively as it normally does.
2. The compressor may make loud noises or vibrate excessively.
3. The pressure relief valve may release excess refrigerant, causing a hissing sound.
4. The high-pressure safety switch may shut off the AC system to prevent damage.

Solution: Replace The AC Pressure Switch.

To install a new AC pressure switch in a car, you must gather the necessary tools and materials to complete the job. 

Tools:

1. Pair of pliers
2. A flat-head screwdriver
3. Replacement pressure switch
4. A wire crimper

Step 1: Locate the faulty oil pressure switch, typically near the AC compressor. The pressure switch can also be mounted on the A/C pressure switch line or in the accumulator. 

Step 2: Once located, disconnect the negative battery cable first to avoid any electrical hazards. 

Step 3: Disconnect the electrical connections from the old switch and any other connections that may be present. 

Step 4: You can remove the faulty AC pressure car switch using the pliers and screwdriver. 

Step 5: You will need to install the new AC pressure switch. This involves connecting the electrical and other connections to the new switch and mounting it in the car. Tighten the new switch using pliers until it is securely in place.

Step 6: Reconnect the negative battery cable. 

When the entire process is completed, you can turn on the car and test the AC pressure switch to ensure it works correctly.

The expense of replacing an air conditioning refrigerant pressure switch is between $260 and $280. This total incorporates labor expenses of $60 to $75 and parts priced around $205. 

This estimation does not include any taxes or supplementary charges, and the specific make and model of the vehicle or the location is not considered.

Reason 3: Low Refrigerant Levels

Low refrigerant levels in cars are caused by a refrigerant leak. When the refrigerant level gets too low, it causes the AC fuse to blow repeatedly. This happens because the low refrigerant level prevents the AC compressor from getting the right amount of pressure it needs to operate efficiently.

Symptom: Hissing Sound Near The AC Compressor

There will be a hissing sound near the AC compressor, or the AC can’t provide enough cooling when running.

Solution: Repair With Leak Sealants

Step 1: The first step is to locate and clean the leaking area. Inspecting the area around a leak can be done by utilizing a torch. If any noticeable dampness or staining is present, it can be cleaned with a moist cloth or sponge. Also, a vacuum designed for wet and dry use can remove any liquid.

Step 2: Next, seal the leak using a sealing compound. 

Step 3: Subsequently, utilize a vacuum pump to remove any residual moisture and regulate the refrigerant pressure in accordance with the manufacturer’s guidelines. The  information regarding the manufacturer’s guidelines can be obtained from the user manual or the official website of the manufacturer.

Step 4: Check the AC fuse to confirm it hasn’t blown. 

The air conditioning system should run smoothly again when you are done with the process. It is recommended to seek assistance from a professional to ensure proper task completion. Attempting to handle the task solo may not yield optimal results.

Reason 4: Damaged Wire Harness

A poor wire harness connection resulting from a damaged wire harness can lead to the AC fuse in a vehicle. This is often because the damaged wires can result in short circuits, leading to excessive current flow and subsequent fuse blowout.

Symptom: Short Circuit

A damaged wiring harness can cause a short circuit which may lead to sparks and fires.

Solution: Replace The Wires

Tools:

1. Wire cutters,
2. Wire stripper tool,
3. Electrical tape or zip ties.
4. Screwdriver

Step 1: Locate the wiring harness for the AC system in your vehicle. The location may vary depending on the car brand and model.

Step 2: Cut the old wires with the wire cutters and remove them from the wiring harness.

Step 3: Strip the ends of the new wires with the wire stripper tool and connect them to the wiring harness. Make sure the connections are secure and tighten them nicely using a screwdriver. 

Step 4: Secure the new wires to the wiring harness with tape or zip ties. Electrical tape or friction tape is recommended.

Step 5: Reinstall the wiring harness into the vehicle and reconnect any other removed connections. Do reconnection in the reverse order that was connected. 

Test the new wiring connections using a multimeter to ensure they function correctly. When using a multimeter to test the wiring connections, reading within the designated range (commonly 12 volts for a vehicle’s electrical system) indicates proper functionality. 

On the other hand, if the reading registers as low or shows a zero value, it may indicate that the connection is not secure or there may be an issue with the wiring.

Then, test the AC system to ensure it is functioning correctly and that the fuse won’t blow again.

Reason 5: Malfunctioning Field Coil

A field coil is an electromagnet that is used in some types of AC systems, particularly in older ones. It is made up of a coil of wire that is wrapped around an iron core, and when an electric current flows through the wire, it creates a magnetic field.

However, newer AC systems typically use a different type of compressor called a scroll compressor, which does not use a field coil. Instead, it uses two spiral-shaped scrolls that compress the refrigerant.

When a field coil malfunctions, it can draw too much current, causing the AC fuse to blow. This is because the current flowing through the field coil is much higher than it should be, creating an overload that then trips the fuse.

Symptom: Electric Motor Current Surging

If the field coil is functioning correctly, it will have a current range of 3-4 amps. However, if there is damage, its current may exceed 10 amps, leading to the AC fuse being tripped due to the heightened energy flow.

Solution: Replace The Field Coil

Step 1: Loose the passenger side front wheel by loosening its nuts.

Step 2: Raise the car using a jack and secure it with car stands.

Step 3: Take off the passenger side front wheel to access the system.
Step 4: Remove the splash guard/skid plate.

Step 5: Use a loaner tool and socket wrench set to loosen the timing belt. Also, unplug the compressor and loosen its 4 bolts with a socket wrench.

Step 7: Gently move the compressor to the hood area and secure the top freon line to the mounting frame.

Step 8: Use an AC clutch holder tool to remove the nut holding the clutch to the pulley.

Step 9: Take off the snap ring using tools such as the clutch pulley puller to remove the pulley.

Step 10: Take off the second snap ring and remove the grounding green wire and the clamp holding the red/green wire to the compressor.

Step 11: Slide out the field coil to replace the coil and reattach the clamp and grounding wire.

When the entire work is completed, reverse the steps to complete the process.

Reason 6: Disengaged Compressor Clutch And Clutch Coil

The car’s AC fuse may blow if the compressor clutch is broken or disengaged and the compressor is still running and drawing too much current. This is because the compressor can’t restrict the flow of refrigerant properly. 

Symptom: AC Not Working Properly

No power is transferred from the engine to the compressor. So, the compressor cannot properly compress the refrigerant, which is necessary for the AC system to cool the air.

Solution: Replace The Compressor Clutch

Tools: 

1. A set of wrenches
2. A socket set
3. A torque wrench

Step 1: The first step in replacing the compressor clutch involves taking out the skid plate situated at the front of the vehicle. This will provide access to the compressor clutch.

Step 2: Once the skid plate has been taken off, the belt connected to the compressor clutch must be uninstalled. This can be done by loosening the bolts on the belt tensioner and then sliding the belt off the pulleys.

Step 3: Once the belt has been removed, the clutch must be detached by unscrewing the bolts that attach to the motor.

Step 4: Once the clutch has been removed from the engine, it will need to be removed. This includes taking out the clutch plate, the bearing, and other connected pieces.

Step 5: Once the clutch has been taken apart, the new parts must be put back together. This involves putting the clutch plate, bearing, and other attached components back in place.

Step 6: Once the clutch has been taken apart, the new parts must be put back together. This involves putting the clutch plate, bearing, and other attached components back in place.

Step 7: Once the clutch has been put in place, the lug nuts must be securely tightened. This will guarantee that the clutch is safely attached to the engine.

Replacing the compressor clutch can be tricky, but one should take time and ensure all components are correctly installed. A professional must do the job if any doubts arise regarding the steps or the need for proper tools.

Reason 7: Overheating

A car can overheat for several reasons, such as a low coolant level and a clogged AC Condenser. These issues can cause the engine to become too hot, and the AC fuse can blow due to an overload of electricity caused by the heat.

Symptom: Loss Of Cold Air From The Air Vents

System overheating reduces the cooling capacity caused by a lack of refrigerant. The cold air is escaping due to broken components in the system.

Solution: Flush The Cooling System And Clean The Radiator.

Precautionary Guide:

1. Check the coolant level regularly
2. Never run the engine without coolant in it
3. Never overfill the coolant system
4. Wear safety glasses and protective gloves
5. Any repair work should be done by a certified professional

Step 1: Flush the cooling system to remove any dirt, debris, or buildup of rust and corrosion. This can be done using a coolant flush kit available at most auto parts stores.

Step 2: A radiator brush or pressure washer can eliminate any residue from the fins.

Step 3: After cleaning the radiator, you can top it up with water or antifreeze. 

Reason 8: Faulty Cooling System Capacitor 

If the cooling system capacitor is not functioning correctly, it may lead to an AC fuse being blown. This is due to the motor drawing too much current, which causes an excess of current that subsequently overloads the fuse and causes it to blow.

Symptom: Fluctuations In Electric Current

Intermittent electric currents in a capacitor can be detected by measuring the voltage across it and comparing it to the expected voltage for the given capacitance. 

The voltage reading of a capacitor can indicate if there is an issue, with fluctuations up to +/- 10% being average.

Solution: Replace The Capacitor

Step 1: First, you must disconnect the battery from the car. This will ensure that no power is running through the system while you are replacing the capacitor.

Step 2: You will need to locate the capacitor after that. In most cars, the capacitor is located near the radiator. The location may vary depending on your car brand and model; check the user manual for the exact location.

Step 3: Then remove the faulty capacitor. Carefully unscrew the screws holding the capacitor in place, then gently pull the capacitor out.

Step 4:Here, you will be installing the new capacitor. Ensure that the new capacitor is securely installed and that all the screws are tightened.

Step 5: Reattach the battery by ensuring that all connections are secure before turning the car back on.

Following the points outlined, you can make the car’s cooling system run as efficiently as possible.

The AC Fuse Blowing Prevention Guide In Vehicles

It’s essential to know how to prevent a fuse from blowing to keep your car in a good and safe condition. 

1. Always use the correct size fuse or amp rating for your specific application. If the fuse is too large, it won’t react to a power surge quickly enough and could cause the circuit to overheat and blow.
2. Inspect for frayed wires, loose connections, and other signs of damage and replace them as needed.
3. Make sure you’re not overloading a circuit. Keep an eye on the wattage of any appliances you’re plugging in and don’t exceed the rated capacity of the circuit.
4. Keep your fuse box clean and debris-free to prevent any issues.
5. It is of utmost importance to keep your car in top condition by regularly servicing and maintaining it.
6. Make sure to keep the car’s refrigerant levels up, clean the air filter regularly, and service all other vehicle parts.

Following these tips can help prevent fuses from blowing and keep your electronics powered and your home or car functioning correctly.

FAQs

Bottomline

There could be various reasons to answer why my ac fuse keeps blowing in my car. To determine the exact cause, it is best to seek the help of a professional automotive technician, who can diagnose the issue and recommend the necessary repairs.

We hope we have helped you the right way; it is time to go.

Adios!