Car Air Conditioner Repair: Air Conditioner Blows Hot Air

What You'll Need
Air Conditioning Manifold Gauge Set

When doing car air conditioner repair, adding freon isn't always what will fix it. However, adding this coolant may be the most common fix for some. Here are a few simple steps to take in diagnosing the problem before adding any freon coolant.

Step 1 – Check for Coolant Leak or Blown Fuses

Check to see if your system has any leaks in it. There is a possibility that refrigerant (freon) could have been lost due to a compressor leak. You could have a leak in the air conditioning hose also. If there are any leaks, they will need to be repaired before adding any freon. You can identify a leak by listening for a hissing sound in your air conditioning system. Oil drops found around the air conditioning hoses and pipe fittings can also be a good indicator that there is a leak. There is a special tool that can find air conditioning freon gas which is another sign of a leak. You can also use dye to pinpoint a leak.

You may also need to check for any fuses that may have blown. If you have a blown fuse and decide to replace it, you still may have a problem as you will need to find out what's causing the fuse to blow. Check the wiring too.

Step 2 – Read the High and Low Side Pressure Readings

Attach the air conditioning manifold gauge set to see if the cooling system has enough pressure. If there is enough freon in your system, a low pressure could still be the problem. Measure the air temperatures in the car. If the air conditioning starts to blow out cold then gets warm, your system could have moisture in it that freezes up. Listen for any constant or loud noise. Any noises can be a result of the compressor, or a belt that may need to be replaced or fixed. If the belts are all okay, you will need to check the power supply for the compressor. The compressor may need to be replaced.

Step 3 – Add Coolant Back to Your Car's Air Conditioning System

Connect the recharging hose into your system. The hoses on the gauges connect to the air conditioning compressor. The shorter hose attaches to the can of freon. Open the valve on the freon can for a couple of seconds to remove the air from the system. Make sure the hose connection is tight again and close the valve back. Turn on your car, and turn the air conditioner on up to high. Open the valve slowly for the low side manifold to allow the freon to enter into the system. Close the valve and take the hose off from the low side fitting after the freon can is empty. Do not hastily remove can because Freon still remains in the can. These steps may be repeated if you need to add more than one can of freon.