Car Air Conditioner Won't Take Freon

adding freon to car AC
  • 1-8 hours
  • Intermediate
  • 50-1,200
What You'll Need
Freon charging hose kit
Refrigerant manifold gauge set
Service manual
Full goggles
Repair parts
What You'll Need
Freon charging hose kit
Refrigerant manifold gauge set
Service manual
Full goggles
Repair parts

You notice your car air conditioner is not performing as well as it should, so you decide to add some Freon to top off the system. What's the best method? Follow along and we'll discuss refilling your car air conditioner with Freon.

Hazard Warning: Refrigerants like Freon can be dangerous. Familiarize yourself with the risks and take precautions by wearing protective gloves, goggles, and a face mask, and working in a well-ventilated area. Always read product warning labels carefully, and never expose refrigerants to flames, sparks, or hot surfaces. Never trap liquid refrigerants between valves with no pressure relief device, and replace any pressure relief devices that look dirty or worn.

Compressor Rotating

Start your engine, turn on the air conditioner, and check whether the compressor clutch shoe is rotating with the pulley. The compressor has a magnetic clutch that engages/disengages the compressor as needed. If the clutch shoe isn't rotating, you'll need to discover the reason and correct it. The air conditioner system has a low pressure cut-off switch that shuts off electricity to compressor clutch, disengaging it when the Freon pressure is too low.

car AC compressor unit

If the compressor clutch shoe is not rotating, but the pulley is, then you can unplug the electrical connection on the low pressure switch and put a jump wire into the harness jumping the connection on both terminals. This should engage the compressor clutch. Now that the compressor is rotating, you can attempt a recharge.

Auto parts stores sell a charging hose/can tapper charging kit that you can connect to low side charging port following instructions provided with the charging kit.

hose/can tapper charging kit for car ac

These recharging kits have some inherent dangers, and the instructions provided should be followed meticulously. Safety goggles are a must when working with Freon as escaping liquid refrigerant can freeze your eyeball causing blindness. Gloves are a good choice as the escaping Freon can be extremely cold and the fittings on the air conditioner system will get very hot when system is operating. Tap Freon can and open valve to begin charging.

Keep the Freon can upright to only charge with gaseous Freon. Turning the can upside down will charge with liquid Freon and should only be done by professional AC technicians. Charging with liquid Freon can overload the system, dilute the circulating oil, and cause damage to the compressor. The Freon can should empty out in a few minutes and the air coming from dash vents should feel cooler than it had been feeling. If the Freon can isn't getting lighter in weight, then you'll need to change tactics.

Connect Refrigerant Manifold Gauge Set

car AC manifold gauges

Connect a refrigerant manifold gauge set to the system by connecting blue hose to low side port and red hose to high side port. Turn on the valves and read the gauges. Note whether there's a pressure differential between gauge readings. If the gauges read near the same, it indicates the compressor is not functioning correctly, possibly due to internal components broken such as a reed valve. Repair or replacement of the compressor is in order to get it functioning so the system can be charged.

If the high side gauge is reading very high pressure while at same time low side gauge is reading very low pressure, that indicates a blockage in the free flow of the Freon. This usually occurs at the expansion valve/orifice tube and will require a replacement and/or cleaning of component.

A pressure differential of at least 150 psi will allow a Freon recharge by connecting the yellow hose from the refrigerant manifold gauge set to the can tapper and turning on the valve of the tapper, purging the hose and then turning on the low side valve. The air conditioner system should begin recharging at this time.

It will take several minutes to empty a can of Freon. Continue adding Freon until the readings of the gauges conform to the specifications for your automobile. Since the air conditioner performance will vary between systems, follow specifications for your particular application.

Remove Manifold Gauge Set

Disconnect the manifold gauge set, being careful not to burn yourself as the fittings will be extremely hot. Remove the jump wire from the low pressure switch and reconnect the wiring harness. Now you can relax and enjoy the cool air from your freshly recharged air conditioner and have the satisfaction of a DIY well done.

Car Air Conditioner Freon FAQ

How do I know if my AC compressor is bad?

Sometimes, your car air conditioner is not blowing cool air, not because of a lack of freon but because of a faulty compressor. If your AC compressor is damaged, it may make noises that sound like rattling.

You may also notice a strange odor when you turn on the AC, another indication that the compressor is bad.

How do I know if my car needs freon?

The biggest indicator that your car needs freon is that the air is blowing warm instead of cool. You may also notice leaking, indicating that the car is losing freon.

How much does it cost to fill a car AC with freon?

The price of filling a car with freon to get the AC blowing cool air again varies depending on the car because the size of freon tanks is not standardized across all makes and models of vehicles.

Expect to pay anywhere from around $150 to $300, on average, to replenish your car's freon supply.

Can I add freon to my car myself?

There are air conditioning recharge kits available for those who want to recharge their car AC. These kits are highly DIY-friendly and readily available at home improvement stores.

However, these kits can really only e used in cars made after 1994 because standards changed. No matter when the car was made, it is pretty tricky to add freon to a car on your own or even to use a kit.

If you make a mistake, you could do damage to the air conditioner and make things much worse when it comes to running the AC in the future.

How long does AC freon last in a car?

If you drive a normal amount of time in your car and run the air conditioner an average amount, expect it to work well for three to four years before the system needs to be recharged. The more you drive, the less amount of time the AC will work properly.