How to Put Freon in a 1999 Ford F-150 Pickup

by Lee Sallings
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Adding refrigerant (freon) to your 1999 Ford F-150 pickup is a common home auto repair project. The air conditioning system in your truck uses R-134A refrigerant that is available at your local auto parts store. Care must be taken to prevent overcharging the system which will result in poor cooling and possible damage to components. Use a set of air conditioning gauges to help identify when the system is full to prevent overcharging.

Step 1

Attach the A/C gauge set to the service ports in your 1999 F-150. The high pressure line service port is located on the passenger side of the truck, near the coolant reservoir, and is protected by a black plastic cover. The low pressure side service port is located on the accumulator near the passenger side of the firewall and is also protected by a plastic cap. In this truck, the ports are different sizes, and the gauge set can only be installed one way. Pull back on the quick-disconnect ring on the red hose fitting and snap it onto the high pressure port. Install the blue, low pressure hose, in the same way, on the low pressure port.

Step 2

Set the A/C controls on the dash to max A/C and medium blower speed. Start the engine and observe the gauge readings. It may take a few minutes for the gauge readings to stabilize. The low pressure (blue) gauge should read 40 PSI, and the high pressure gauge (red) should read 350 PSI in a fully charged system.

Step 3

Screw a can of freon to the can tap on the end of the yellow service hose on the A/C gauge set. Turn the wing screw on the tap all the way in to pierce the top of the can. Unscrew the wing screw to open the can. Open the low pressure side (blue) valve on the gauge set and allow the can of refrigerant to flow into the system. Close the valve when the can is empty and observe the gauge readings. Add additional cans of refrigerant, as needed, to fill the system until the pressures are between 40 and 350 PSI.

Step 4

Turn the engine off and wait for a few minutes for the pressures in the system to drop. This will prevent damage to the service ports on the truck. Reinstall the plastic caps on the ports.

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