As you remember the hot, sultry days of last summer, perhaps it suddenly occurs to you that you never did fix the air conditioning system in your car. You also just found out that the Old Farmer's Almanac expects the coming summer to be even hotter and slightly drier than normal. Aside from bringing the car into the shop and hoping the bill won't be more than you're prepared to pay, you can do a few simple checkups to get those vents flowing and keep yourself cool, calm and collected.
Start your ignition, and turn on the air conditioner. Is it blowing cold air, cool air or nothing at all? Most problems involve leaks, defective wiring or the compressor. It may also be as simple as debris (leaves, bugs, etc.) covering the condenser and blocking air, or a clogged cabin air filter, which can easily be replaced.
First, check for signs of a leak, and make sure that the compressor is engaged. You can easily pop the hood to examine the hoses. Make a mild soap solution, and put it in a spray bottle. Turn the cooling system on, and spray the hoses. Be careful not to get any spray on the alternator. If there is a leak, you'll see bubbles. To seal the leak, go to your local auto parts store and purchase an auto air conditioner sealant, a gauge and R134a refrigerant; you'll also need to rent an air-conditioning system vacuum. The sealant will not solidify inside the system, but be sure to follow the manufacturer directions. If your car was made before 1995, it needs R12 refrigerant (unless it has been converted) and will need to be seen by an air conditioning specialist.
Next, make sure that the cooling fans on the radiator or condenser are running. If they aren't, there may be an electrical problem. Check the fuses first to make sure none have blown. This step could save you a lot of unnecessary time. If one has blown, replace it (always with a fuse that has the same capacity). But if there is an issue with the wiring, simply replacing the fuse may not solve the problem. All electrical components need adequate voltage to operate, so the car battery needs to be fully charged and have a good output. You will need a voltmeter to check the battery output and an ohm meter to trace the resistance through the wires, but do not use the ohmmeter on a live wire. Both of these devices, and how-to instructions, can be found at auto retail companies like AutoZone. Using the voltmeter, start your tracing by ensuring that there is voltage at the circuit. Remember, the basic premise is that anything electrical requires continuity from one end of the wire to the other; if you have to jiggle a wire for continuity, there is probably a break in the wiring, and the wire should be replaced. Never poke a hole in the insulation to get to the wire. Refer to a wiring diagram if possible to ensure that you are testing the correct wires. Chilton and Haynes make automotive electric wiring schematics manuals. These tools and aids will help you safely and easily execute this test.
To rule out the third common problem, the compressor, turn the engine on, and set the air conditioning to maximum strength and the fan on high. The clutch, the center part attaching the pulley to the compressor shaft, should be turning. If it's not engaging, use a voltmeter to check for power to the compressor. If there is power, the clutch may need replacing. Visit your local auto parts store for a new or rebuilt compressor/clutch combination. If the clutch engages and disengages rapidly, you might need more refrigerant in the system. If the refrigerant is very low, it might not be enough to trip the low-pressure cutoff switch that cycles the compressor. So, you can buy a recharge kit from your local auto parts store.
Whenever you're adding refrigerant, you must add it correctly and precisely. Use the low-side port of the air conditioning system, the location of which should be shown in the car manual. Follow the lines from the compressor to a nozzle near the bottom of the car. And make sure you wipe off the service port completely before using it so that you won't clog the line with dirt or debris. Use the gauge to make sure you are not overfilling the system.
As you start planning summer road trips and activities, take the time to nip any car air conditioning problems in the bud. When the sun's beating down and it comes time to pack up and go, you'll have no reservations about heading for the horizon.