How to Troubleshoot the Air Conditioning on Cars

by Contributing Writer; Updated June 12, 2017

The air conditioning system in your Jeep car compresses a refrigerant and blows the resulting cold air into the passenger cabin. When this system is not working properly, it can be because the pressure in the AC lines is too low, or because the compressor has failed. Replacement compressors can be purchased from most auto parts stores. Recharging your air conditioning system can be done by most mechanics. However, before you replace anything, you should troubleshoot the problem so that you know what's wrong.

Under The Hood:

 How to Troubleshoot the Air Conditioning on a Jeep Liberty

Open the fuse panel cover by pulling down on the cover with your fingers.

Pull the fuse for the air conditioning using the fuse pullers in the fuse panel. Use the fuse diagram on the underside of the fuse panel if you are having trouble locating the fuse for the air conditioning.

Check the metal strip in the fuse. If the fuse is blown, replace it with a new fuse of the same amperage.

Open the hood of your Jeep Liberty. Locate the low pressure air conditioning line. The air conditioning lines will be steel lines running on the left side of the engine bay. The low pressure line on your Liberty is marked with a blue valve cap on the line.

Unscrew the blue valve cap and screw on the air conditioning pressure gauge.

Turn the knob on the pressure gauge counterclockwise to allow pressure into the gauge.

Check the gauge reading. Your AC pressure gauge should be color coded. If the needle on the pressure gauge sits within the green band, the pressure in the air conditioning system is fine. If it falls outside of this range, then you will need to have the AC system checked.

Check the belt that wraps around the pulley on the end of the Liberty's air conditioning compressor. The belt teeth should not be damaged in any way. If they are, replace the belt.

Start the Liberty's engine and turn on the air conditioner. If you do not get cold air blowing from the air conditioner within 15 minutes of starting the engine, the air conditioner compressor needs to be replaced.

Items you will need

  • AC pressure gauge

 How to Troubleshoot the Air Conditioning in a GMC Sierra

Start the engine and let it to run for a few minutes to allow the air to cool. Double check the controls to make sure the correct buttons are selected. This may seem simplistic, but human error could be to blame.

Adjust the climate controls. If they are working correctly with the right amount of resistance and stopping at the right places but have no effect on the air then it is probably a simple fuse problem. If they are not working correctly then it is probably a control panel issue.

Get to the fuse box to change the blown fuse in a GMC Sierra by opening the driver's side door and prying off the trim panel to the left of the steering wheel. The fuse can be removed with your fingers. If the Sierra was purchased new there should be replacement fuses in the fuse box.

Check the control panel next in your GMC Sierra. Remove the trim plate bezel surrounding the center instrument panel. Pull of the storage tray and the accessory switch.

Unscrew the four screws holding the climate control assembly in place, push in the retaining tabs and pull the control panel out. Unplug the electrical connector. Sierra models older than 2001 have no retaining tabs or accessory switch.

Listen for the blower motor while the engine is running and the air is on. There are two different possible blower motors in a GMC Sierra. Both are easily accessed from under the hood. The Delphi will sit vertically, while the Visteon sits horizontally. In both cases, remove the sound insulation panel, unplug the electrical connector and unscrew the three screws holding the blower motor into place.

Items you will need

  • Screwdriver

 How to Troubleshoot the Air Conditioning in a Chrysler Sebring

Start by adjusting the dials that control the air conditioning. Make sure that they work properly, as they did before the air conditioning problems. If they don't feel right, with the right amount of resistance, then the problem is simply a blown fuse. If they work properly but have no effect on the air, then it is a control panel problem.

Replace a blown fuse in a Chrysler Sebring. The fuse box is located to the left of the steering wheel on the side of the dashboard. Pop off the panel cover, remove the fuse with a small pair of pliers and replace with a new fuse of the same wattage.

Find the control panel in a Chrysler Sebring by first disconnecting the negative battery cable, removing the console box, setting the temperature to "full hot," disconnecting the temperature control cable, removing the gear selector trim panel, unscrewing the panel cover and removing the radio bracket.

Listen for the blower motor to make sure it is working. With the engine on, turn on the air and adjust the pressure. The normal accompanying sound indicates the blower motor is working properly. If it is not, remove the blower motor in a Sebring by removing the right side instrument panel, unplugging the electricity to the blower fan and then unbolting it.

 How to Troubleshoot the Air Conditioning in a Jeep Grand Cherokee

Start the engine and adjust the climate controls. If they seem to work fine but have effect on the air then the problem is probably a simple blown fuse. If the controls do not work correctly then the problem is probably with the control panel. If you cannot hear the sound that accompanies turning the air from low to high, then the problem is likely with the blower motor.

Replace a blown fuse easily. There are three fuse boxes in a Jeep Grand Cherokee, and the one that powers the air conditioning is found under the instrument panel to the left side and slightly below the steering column. The correct fuse is the red number five.

Disconnect the air bag system first before gaining access to the control panel. Do this by disconnecting the black negative battery cable and waiting at least two minutes.

Remove the center section of the instrument panel on the dashboard that surrounds the air conditioning and heating controls. Unscrew the four screws that hold the climate control assembly into place. Pull the controls out.

Get to the blower motor in a Grand Cherokee by first disabling the airbags. Unscrew the glove box and remove it. Unscrew and remove the blower motor wire harness found directly behind the blower motor. Unscrew three screws holding the blower motor into place and then remove the motor.

Items you will need

  • Screwdriver

 How to Troubleshoot the Air Conditioning in a Honda CR-V

Start the engine of your Honda CR-V and allow the engine to warm up before beginning the troubleshooting.

Check the coolant levels in the coolant reservoir. Lift the hood of the vehicle. Find the reservoir in the very front of the vehicle on the driver's side. It is a plastic white jug. Lift the lid and shine a flashlight into it. Look at the side of the jug to make sure the level of the coolant is in between the low line and the full line.

Open the interior fuse box to make sure the fuse controlling the AC is not blown. The fuse box is found in a Honda CR-V by opening the driver's door and prying off the trim panel on the very side to the left of the steering wheel. The fuse needed is number 17 and is 7.5 amps.

Switch the air to hot to see if the heater is malfunctioning too. If neither the heater nor the air conditioner work, then there is a shortage in the wiring.

Adjust the air from low to high and listen for the sound of the blower motor to increase. Blower motors need replaced in ageing vehicles commonly. Find the blower motor in a Honda CR-V by prying of the lower foot panel on the passenger's side. Unplug the electrical connectors and pull the blower motor downward.

Items you will need

  • Screwdriver

  • Flashlight

  • 7.5 amp fuse

 How to Troubleshoot the Air Conditioning in a VW Jetta

Start the engine and let it run for a few minutes to allow the air to cool. Adjust the climate controls. If they seem to work fine but do not effect the air then it is a simple blown fuse. If they do not feel right at all, then it is probably the control panel. If you cannot hear the normal blowing sound that accompanies the air conditioning, then it may be a broken blower motor or fan.

Replace a blown fuse quickly and easily. Find the fuse box in a VW Jetta behind a small rectangular trim panel on the passenger side directly in front of where a passenger would sit. Pull the blown fuse out with your fingers and replace it with one of equal amperage.

Disconnect the black negative battery cable before getting to the control panel. Remove the glovebox cover. Remove the center console next by unclipping the cover caps and removing the screws.

Pull out the ashtray insert. Slide the ashtray forward and pull out far enough until cigarette lighter connector can be pulled out too. Unbolt it. Pull out the center console upward over gear shift lever.

Unscrew and remove the glove box. Pull off the trim around the steering wheel, and the trim around the heat controls. Unscrew, unplug and remove the control panel.

Remove the lower trim footwell panel on the passenger's side to get to the blower motor. You will see the blower motor right away. Unscrew it and remove it.

Items you will need

  • Screwdriver

 How to Troubleshoot the Air Conditioning in a Nissan Sentra

Start the car and let it run for a few minutes for the engine to heat up.

Adjust the climate controls on the dashboard to make sure they are correctly working. If the controls seem to work but have no effect on the air pressure or temperature then the problem is probably a blown fuse. If you cannot hear the accompanying blowing sound when adjusting the controls then it is probably a broken blower motor. If they are not working properly at all, then the problem is probably in the control panel.

Find the fuse box in a Nissan Sentra to the left of the steering column on the driver's side. Open the driver's door and pry off the side panel. There is a diagram on the inside of the fuse box cover that will indicate which fuses control the air conditioning.

Remove a busted blower motor by first removing the glove box and then the trim that surrounds it. Remove the three bolts holding the blower motor into place, and finally the blower motor.

Get to the control panel in a Nissan Sentra by first disconnecting both negative and positive cables to the battery unit. Remove the instrument panel by removing the two lower panel screws and the lower panel on each the driver's side and then the passenger side.

Unscrew the six steering column cover screws, the cover and combination switch, the two cluster lid "A" screws, the cluster lid "A", the three combination meter screws, and then disconnect the electrical harness connector and remove the combination meter. Remove the ashtray next. Remove the cluster lid "C" mask, screw and the cluster lid "C".

Take off the eight audio and air conditioning control panel screws, the electrical connectors and then the assembly itself. Remove the transmission shifter trim. Remove the rear console mask, the four screws and the rear console. Remove the four front console screws and the front console. Remove the front pillar garnish. Remove the lower dash side garnish. Remove the instrument panel mask. Remove the instrument nuts and bolts and finally the instrument panel.

Items you will need

  • Screwdriver

  • Monkey wrench

 How to Troubleshoot the Air Conditioning on a 2001 Jeep Cherokee

Turn on your Jeep's engine and turn on the air conditioning. Let it idle and check to make sure that the electric fan in front of the air conditioning compressor is on. If it is not, then this could cause your air conditioning system to perform badly at idle.

Touch the low-pressure pipe (of the two pipes leading out of your Jeep's air conditioning compressor, it will be the larger one) to see if it is running cold. If this pipe is not cold to the touch, then your compressor is not working properly or your system needs more refrigerant.

Turn off your car and hook up an air conditioning pressure gauge to the high and low pressure sides of your air conditioning system. On an 80 degrees F day, the low side for your Jeep should be between 32 and 41 psi and the high side should be between 200 and 260 psi. If your Jeep's psi is under this, recharge the system with more refrigerant. Refer to your owner's manual for further psi numbers.

Have someone else go inside your car and turn on the engine. Then have them turn on the air conditioner as you watch to see if the compressor turns on. If it does not, the compressor is faulty and may need to be replaced. This is most likely the problem if you air conditioner blows warm air all the time.

Use soapy water on the rubber hoses of your air conditioning system. If the water begins to bubble up, then air is escaping from the system and the air conditioning is losing refrigerant. This will cause your air conditioner to gradually lose cooling power. If this is the case, the faulty hose will need to be replaced or patched.

Check to see if the air conditioner runs cool then suddenly stops working after a number of minutes. If this happens, turn off the air conditioning for a while, then try again. If the same thing happens, there may be too much air in the system, which causes the moisture in the pipes to freeze and eventually block off refrigerant circulation. If this is the case, vacuum pump the system and replace it with new refrigerant.

Items you will need

  • A/C pressure gauges

 How to Troubleshoot the Air Conditioning in a Chevy Corvette

Lift the hood of the car with the engine off and first look for visual clues as to what the problem may be. Look at the compressor. It is cylindrical in shape, sits directly next to the engine and has a belt. Make sure the belt is intact and there is no rust.

Start the engine of the car and allow it to run while looking at the compressor. Look for obvious signs of malfunction. Touch both of the hoses attached to the compressor. The larger one should be cool, and the smaller hose should be warm but not painfully hot.

Listen for the blower motor to make sure that it is running, but not overly loud. Step into the car and play with the air controls on the dashboard to make sure the blower motor is making the appropriate increases and decreases in volume.

Change the fuse if the controls are not working. The fuse box in a Chevy Corvette is on the floor board. Lift the carpet on the passenger side, and then remove the toe-board covering. Pull at the top corners of the panel to gain access to the fuse box. In a corvette, it is fuse number 28 and can be replaced with one of the spares available.