How To Recharge Mustang R134A A/C System

Having a properly charged and healthy air conditioning system in your Mustang is a common luxury that everyone should have. After all, a hot summer day and no A/C is no fun at all. This guide will show any Mustang owner how to charge their system using R134A refrigerant.

Before doing this, it is important to understand how an A/C system works and that a licensed HVAC technician properly empties the system. Be sure and consult the owner’s manual or the underhood sticker to see how much your system takes.

In the case of this guide, our Fox Body has an R12 weight amount which is slightly different because this system has been converted to R134A refrigerant using a premium 5.0 Resto A/C conversion kit. Start at seventy-five percent of the R12 weight and go up from there until the system is properly charged.

To charge the A/C in your Mustang at home, you will need a decent set of manifold gauges, a vacuum pump, PAG oil and a few bottles of R134A refrigerant, and a can tap. Also, be sure and set aside a few hours to get this one accomplished.

1. With the system properly emptied, you can begin by connecting the high and low service ports. The high-side service port is typically found on the line connecting the compressor to the condenser. This is true in our case. Now, the low-side service port is typically found between the compressor and accumulator. This is also true for our application. These two ports are also typically different diameters, so getting them mismatched is almost impossible.



2. Go ahead and connect the vacuum line to the vacuum pump. This connection only needs to be finger-tight.



3. Once connected, make sure the high-side valve is fully closed and the low-side valve is open.



4. Turn on the vacuum pump and let it run for fifteen to thirty minutes.



5. Once the gauge reads thirty inches of mercury for vacuum, close the valve and then turn off the pump.


6. Let this sit for approximately an hour to make sure that there are not any leaks in the system. When that is verified, open the valve and run the pump for an additional thirty to forty-five minutes. Now you can close the valve, turn off the pump and then disconnect the vacuum line.


7. If your system needs oil now would be the time to add it. Pour a little oil into the vacuum line before you connect your refrigerant. Screw the line onto a can tap.



8. Pierce the can of Freon and then open the low side valve.



9. When the first can is empty, close the valve on the low side and then start the vehicle.



10. Turn the A/C on and the fan speed on high.



11. If your compressor does not kick on, check out this simple trick by making a jumper and installing it onto the clutch cycling switch electrical connection.



12. With the A/C still running, pierce another can of Freon and completely fill the system to the recommended amount. Depending on the ambient temperature you are in, your low and high side pressures will differ. Our pressures were spot on since we were working in a room that was approximately seventy degrees.



13. Be sure and remove your jumper and reconnect the clutch cycling switch.



14. Take this time to spray some soapy water over all of your connections to verify that there aren't any leaks present.



15. Use a thermometer to verify the temperature coming out of the vents is blowing cold and you’re all finished!


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Charging an A/C system can seem somewhat intimidating, but hopefully, this helpful guide will persuade you first-timers to give it shot. Remember, have a licensed shop drain the system first before you go about charging your system.

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