What happens if you put too much AC Pro in your car?

Putting too much AC Pro refrigerant in your car’s AC system can cause serious problems. AC Pro is a popular do-it-yourself AC recharging kit that allows you to add more refrigerant (also known as Freon) when the AC isn’t blowing as cold as it should.

What is AC Pro?

AC Pro is a can of R-134a refrigerant designed to recharge vehicle AC systems. It includes a built-in gauge and hose so you can connect it directly to your car’s low-pressure AC port and add refrigerant when needed. The main advantages of AC Pro are that it’s inexpensive and easy to use yourself.

R-134a is the approved, EPA-compliant refrigerant for most modern vehicles. Older cars used a refrigerant called R-12 (Freon) but this was phased out in the 1990s due to environmental concerns. All cars made since around 1995 use R-134a.

How Much AC Pro Should You Use?

The AC Pro kits are designed as a one-can, single-use product. Each 12 oz can contains enough R-134a refrigerant to fully recharge a small AC system or add a partial recharge to a larger system. The packaging states it will add 1-2 lbs of refrigerant.

You should only use one can per recharge. Adding more refrigerant than the system is designed for will lead to serious problems (covered in the next section). Do not discharge more than one can into the AC system without first having a professional evaluate the system.

What Happens if You Put Too Much AC Pro?

Adding an excessive amount of AC Pro or other R-134a refrigerant can damage your air conditioning system. Potential problems include:

  • Over-pressurizing the AC system
  • Stressing the AC compressor
  • Decreased cooling efficiency
  • Refrigerant leaks
  • Contaminating the refrigerant oil
  • Tripping low and high-pressure safety switches, disabling AC operation

Let’s look at each of these issues in more detail:

Over-Pressurizing the System

The air conditioning system in your vehicle is designed to hold a specific amount of refrigerant. Adding too much refrigerant over-pressurizes the system since there is nowhere for the excess gas to expand.

The high pressures caused by overcharging will strain system components like the compressor, condenser, and hoses. This can lead to leaks, damaged seals, and even catastrophic component failures.

Damaging the Compressor

One of the most serious risks of overcharging the AC system is compressor damage. The AC compressor is the heart of the system – a mechanical pump that pressurizes refrigerant gas during the AC process. It has tight tolerances and is susceptible to damage if subjected to abnormally high internal pressures caused by overcharging.

Too much refrigerant can overwhelm the compressor and cause it to overheat or break down prematurely. A damaged compressor usually requires complete replacement, an expensive repair.

Decreased Cooling Efficiency

Adding more refrigerant than needed will actually reduce your AC system’s cooling capabilities. The proper charge amount is essential for peak operating efficiency.

When overcharged, the compressor struggles to fully vaporize excess liquid refrigerant. This leaves less capacity for absorbing heat energy, resulting in warm air from your vents. Plus, higher head pressures impede the condensation process.

Causing Refrigerant Leaks

High internal pressures from overcharging place strain on AC components and seals. O-ring seals and gaskets can be forced out of their grooves. Leaky fittings and compromised components then allow refrigerant to escape.

Once a refrigerant leak starts, it’s difficult to stop. The AC system needs to be repaired to re-seal any fittings or replace damaged parts. Adding more refrigerant only leads to further leaks until underlying problems are fixed.

Contaminating Refrigerant Oil

Moisture is the refrigerant system’s worst enemy. Water contamination causes refrigerant oil to break down and lose its lubricating properties. Eventually the oil can become acidic and corrode the compressor from the inside.

Overfilling the system with liquid refrigerant increases risk of water contamination. It allows excess moisture to mix with the compressor oil. Preventing moisture infiltration is why AC recharging should always be done quickly with the system sealed.

Triggering Safety Switches

Your vehicle’s AC system has high and low-pressure switches designed to disable the compressor if pressures exceed safe limits. Adding an overcharge of refrigerant may be enough to trip one of these switches.

When a safety switch trips, the compressor will stop running and you’ll lose AC cooling. A technician has to reset the switch after evacuating the excess refrigerant. Simply adding more refrigerant without addressing the underlying overcharge problem will lead to repeated switch trips.

Signs Your AC System is Overcharged

Watch for these common indicators that too much refrigerant has been added:

  • High system pressures (over 300 psi)
  • Bubbling sight glass (if equipped)
  • Poor cooling performance
  • Compressor cycling on and off rapidly
  • AC shutoff due to tripped safety switches

High pressures, poor cooling, and tripped low-pressure switches point to overcharging. If you experience these after using AC Pro, have your system inspected by a professional before adding more refrigerant.

Recovering From an AC Pro Overcharge

The only remedy for an AC overcharge is to evacuate the excess refrigerant to lower system pressure. DIYers do not have the proper tools or knowledge to do this safely and legally.

A professional AC service uses a refrigerant recovery machine to safely remove the excess gas and bring your charge down to the proper level. Simply venting refrigerant into the air is illegal due to environmental concerns. Proper evacuation and disposal or recycling of recovered refrigerant is required.

Depending on how much extra AC Pro was added, the technician may need to evacuate and reclaim the entire refrigerant charge, then weigh in the proper amount. Contaminated refrigerant oil would need to be flushed as well.

Damaged components like a failing compressor or leaky evaporator core may also need repair or replacement. Preventing damage is why overcharging needs to be addressed quickly, before it leads to major AC repairs.

How Much Does it Cost to Fix an AC Overcharge?

It’s hard to put an exact price on fixing an AC overcharge, since different vehicles and damage levels will result in different repair costs. However, here are some ballpark estimates:

AC Overcharge Repair Estimated Cost
Refrigerant evacuation and recharge $100 – $200
Compressor replacement $600 – $1,000
Evaporator core replacement $600 – $1,200

Keep in mind these prices can vary greatly depending on your vehicle model and your location. More extensive damage will result in higher repair bills. Your best bet is having an experienced AC tech evaluate your exact situation.

How to Properly Recharge AC with AC Pro

To avoid potential overcharge problems, follow these steps when using AC Pro:

  1. Only add refrigerant when the system is completely empty and has been evacuated of all remaining gas. Adding refrigerant to an existing charge without properly evacuating it first results in overcharging.
  2. Carefully follow the AC Pro charging instructions. Always start with one can only. Only add a second can if the system did not reach a full charge with the first.
  3. Use an AC manifold gauge set to monitor system pressures during the recharge process. High pressures over 300 psi likely indicate overcharging. Stop adding refrigerant if pressures exceed recommendations.
  4. Run the AC system for at least 10 minutes after recharging to ensure the sight glass clears and all refrigerant circuits are fully saturated.
  5. Avoid recharging the system with AC Pro more than once or twice without a thorough system evaluation. Repeated recharging often leads to overfilling.

DIY AC recharging can provide a fast, low-cost way to restore cooling performance if done carefully and only when truly needed. But the only way to accurately charge an AC system is by weighing the extracted and replaced refrigerant – a task requiring professional equipment. Have your AC system periodically inspected to ensure pressures, leaks, and charge levels remain within factory specifications.


Adding too much AC Pro or other refrigerant is one of the most common DIY AC mistakes. Overcharging the system pressures components to failure, decreases cooling performance, and can lead to expensive repairs.

Watch for signs of overcharge like high system pressures and poor cooling. If suspected, have a professional service evacuate any excess refrigerant to prevent damage. With proper procedures, AC Pro can be a quick and cost-effective way to recharge an empty AC system and restore cooling comfort.

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