Does your car’s air conditioner blow cold air when you first turn it on, but then start putting out warm air after a few minutes? Or does the AC seem to work well at high speeds, but barely blow any cold air when idling at stoplights? These are common signs that your vehicle’s air conditioning system has too much refrigerant – also known as being overcharged.
An overcharged AC can lead to a number of problems, from reduced cooling performance to compressor damage. Thankfully, diagnosing an overcharge is straightforward with some basic tools and knowledge. And correcting it simply involves safely evacuating the excess refrigerant.
This handy guide will walk through the common symptoms so you can recognize if your car’s air conditioner is overfilled with refrigerant. You’ll also learn what causes it to happen in the first place, how to confirm the overcharge, steps for properly discharging the extra refrigerant, and tips for recharging the system correctly going forward.
Table of Contents
Do You Notice These 5 Symptoms of an Overcharged Car AC?
While an overcharge may not be hugely apparent at first, certain signs tend to pop up that indicate too much refrigerant in the system:
1. AC Blows Cold Then Warm Air
This is one of the most common indicators of an overcharge. When you first turn on the AC, it blows nice and cold. But after a few minutes, even though the compressor is still running, the air coming out the vents gets warmer and warmer.
This happens because the excess refrigerant can still expand and absorb heat initially. But with too much in the confined space, it can’t evaporate fast enough through the evaporator to continue cooling the air.
2. Cold Air at High Speeds, Not When Idling
Similarly, a car AC system with too much refrigerant may still blow cold at higher engine speeds and air flow, like while cruising on the highway.
Once you come to a stop and idle at a light though, suddenly no cold air comes out. That’s because at low speeds, the saturated evaporator coil can’t dissipate the heat fast enough for the overfilled refrigerant.
3. Short Cycling of AC Clutch
Pay attention to the AC clutch next time you turn the system on. The magnetic clutch should turn the compressor on and off intermittently – but not rapidly cycle on and off.
If the clutch is engaging and disengaging repeatedly every few seconds, this usually signals an overcharge. The high side pressure from too much refrigerant triggers the clutch to cycle quickly.
4. Foggy Air From the Vents
Take a close look at the air coming out of your central and side vents. Is it foggy or misty even when it’s cold? This moisture forming means the evaporator core is icing up.
The overfilled refrigerant can’t properly evaporate through the restricted evaporator passages. So moisture condenses and freezes on the fins instead of cooling the air.
5. High Head Pressure Readings
The most reliable way to confirm an AC overcharge is by hooking up gauges to read the system’s pressure. Most systems should show between 30 – 45 psi on the low side, and around 150 – 225 psi on the high side when operating.
If the high side pressure is consistently greater than 225 psi, that direct indicator points to excessive refrigerant in the AC system.
Now that you know what symptoms to look for, what actually causes a car’s air conditioning system to become overfilled with refrigerant in the first place?
What Are the Most Common Causes of an AC Overcharge?
Many times, an overcharged AC unit simply results from improper refrigerant filling:
- Adding too much refrigerant during a recharge – If the specified amount is exceeded, it will lead to an overcharge. Always follow the factory recharge capacity for your vehicle.
- Leaky AC components – Small leaks in hoses, seals, or gaskets over time can let refrigerant slowly escape. This means there is extra space to hold refrigerant, allowing accidental overfilling.
- Incorrect recharge procedures – Not following the proper steps can result in too much refrigerant in the system. For example, failing to vacuum and leak test before adding refrigerant.
Other Causes of AC Overcharging
While over-filling is the most prevalent cause of an overcharge, here are some other possible contributing factors:
- Blocked condenser – Reduced air flow prevents the refrigerant from condensing properly.
- Messy front condenser – Bugs, debris, and dirt prevent the refrigerant from condensing.
- Damaged evaporator – Restricted, bent, or corroded evaporator coils inhibit refrigerant expansion.
- Compressor issues – Wear, slipping clutch, or failure to provide compression allows excessive refrigerant.
- Broken temperature sensors – Faulty sensors signal more refrigerant is needed when it’s not.
But how can you definitively diagnose that your air conditioner is in fact overcharged? Let’s go over some confirmation and testing steps.
How to Accurately Diagnose an Overcharged AC System?
While symptoms and visual clues can indicate an overcharge, you’ll want to carry out some diagnostic testing to be 100% sure before proceeding.
Using AC Gauges to Check Pressure
The most reliable way to identify an overcharge is to attach AC gauges and verify if the system pressures are too high.
Here is a step-by-step process to check the pressure readings:
- With the car off, attach the gauges to the low and high pressure AC ports, typically found under the hood.
- Start the engine and turn the AC on max, with the temperature set to full cold.
- Look at your AC gauges after a few minutes of operation. The low side pressure will be normal.
- Check the high side pressure reading. If it is consistently higher than 225 psi, that confirms too much refrigerant in the system.
- High side pressures exceeding 250 psi indicate a severe overcharge that should be addressed promptly.
Performing a Dye Leak Test
Since leaks in the AC system often contribute to overcharging, it’s wise to perform a thorough leak test:
- Purchase an AC fluorescent dye kit. Remove any refrigerant from the system.
- Inject the UV dye according to the product instructions.
- Run the AC for at least 15 minutes to circulate the dye.
- Use the UV lamp to meticulously inspect all components for leaks indicated by glowing dye.
- Address any identified leaks using sealants or replacing parts.
Once you’ve verified an overcharge through testing, you’ll want to properly remove the excess refrigerant before recharging the system.
How to Safely Discharge Excess Refrigerant?
With a confirmed overcharge, do NOT just release the extra refrigerant into the air – that would be horrible for the environment. You MUST use proper refrigerant recovery equipment to safely capture it.
Here are the key steps to safely discharge the overfilled refrigerant from the AC system:
Use Proper Refrigerant Recovery Equipment
You’ll need an AC refrigerant recovery machine for this task. Recovery units safely remove refrigerant from a system without releasing it.
Common types of recovery equipment include:
- Self contained recovery machines – Portable all in one units with storage tank.
- Manifold gauge set recovery – Uses manifold gauge set and external storage tank.
- Refrigerant recycling devices – More heavy duty for collecting, cleaning and reusing refrigerant.
Follow all instructions provided with your refrigerant recovery unit for safe operation.
Connect Recovery Machine to AC System
With the air conditioner turned off, connect the recovery machine hoses to the low and high pressure ports on your car’s AC system.
Make sure the hoses form airtight seals. Follow all steps in your machine’s manual for proper setup and connections.
Operate Until Normal Pressures Are Restored
Turn on the recovery machine. It will automatically extract the excess refrigerant, pulling it into the storage tank.
Periodically check the system pressure using your AC gauges during the process. Recover refrigerant until the high side pressure drops down to normal range between 150 – 225 psi.
This indicates the overcharge has been sufficiently discharged from the system.
Double Check Charge Levels Before Recharging
Once the recovery process is complete, confirm head pressure is now in the proper range before recharging the system. Start the engine, turn the AC on max cold, and check the high side gauge:
- If the pressure still seems too high, repeat the refrigerant recovery steps to remove any remaining excess.
- If pressure is now below 150 psi, the system is undercharged after the recovery and will need refrigerant added back.
- When high side reading is between 150 – 225 psi, the system is ready to be recharged properly.
Now that the overcharge has been corrected, let’s go over the proper steps for recharging your AC system with the right refrigerant amount.
Follow These Steps for Properly Recharging Your Car’s AC
Once any overcharge is fixed, it’s critical to follow precise recharge procedures going forward to prevent it happening again.
Start With a Totally Evacuated System
Always make sure the AC system has been fully evacuated using a vacuum pump before recharging. Vacuuming removes any moisture and ensures there’s no pressure in the system.
Add Precise Oil Amount First
The compressor requires a specific amount of lubricating oil to function. Consult the factory spec and add the exact amount of new oil before adding any refrigerant.
Recharge Refrigerant To Exact Specification
Use a refrigerant scale to measure the precise amount of refrigerant charge recommended by the manufacturer – don’t estimate. Slowly add refrigerant, periodically verifying system pressure.
Be vigilant and stop adding refrigerant immediately if pressure starts climbing over 225 psi. Recheck level and carefully add in quarter ounce increments if needed.
Periodically Check System Pressure
Make it a habit to connect gauges and monitor AC head pressure at least seasonally to ensure proper charge is maintained.
And that covers the complete process – from identifying overcharge symptoms, properly diagnosing the problem, discharging excess refrigerant, and steps for correctly recharging your AC system.
Is Your Car’s AC Still Blowing Hot Air? Recap of What to Do
Dealing with an overcharged air conditioner losing its cool? Here’s a quick recap of the game plan:
- Look for key symptoms – like warm air from vents, rapid clutch cycling, and foggy air. High side pressures over 225 psi confirm it.
- Determine the source – did overfilling during a recharge cause it or is there a system leak? Find and address any leaks.
- Recover refrigerant properly – never vent it – use approved recovery equipment to capture excess refrigerant.
- Replace lost oil – add back oil to specs before recharging refrigerant.
- Follow exact recharge procedure – evacuate, leak test, oil, measured refrigerant amount.
- Maintain proper charge – periodically check system pressure to prevent future over or undercharges.
And with that, you can be on your way to keeping the AC in your car blowing crisp, cold air on the hottest summer days. Stay cool!