Man fixing his car's a/c

How to Diagnose and Repair Your Car's A/C

There aren’t many things as satisfying as the cool breeze from your car’s air conditioning. On the flip side, a faulty A/C during an unforgiving heat wave can ruin a driver’s experience. Here’s some advice for finding out the problem with your A/C and fixing it up.

Signs of a Bad A/C

Of course, the most telling sign of a bad A/C is one that doesn’t blow out cold air or has a weak air flow. However, even if your A/C is blowing just fine, it can still turn out to be broken. You can tell its bad if you hear a rattling or screeching upon turning it on. This can be from a bad bearing in the compressor pulley. You can check parts under the hood as well. Signs of malfunctioning include:  a belt that drives the compressor which has fallen off or slips on the compressor pulley, a dirty condenser (sheet of tubing in front of the radiator), or a dirty cabin air filter.

Reasons Behind It

A/Cs typically stop working because of a leak. The refrigerant, that runs through the system drains out through the leak and results in a low refrigerant level. You can verify this by testing the pressure using gauges that connect to the test/load valves (located near the compressor), or going to an auto shop for a pressure diagnostic. If you have a different issue with your A/C, you might have other nonworking components.

The Fix

To see if you have a leak, you can take your car to the auto shop for a pressure diagnostic and leak evaluation, costing around $80 – $150. It’s wise to have professionals refill the system with coolant or refrigerant because often it’s difficult to tell when there’s too little or too much. A legitimate fill up can cost around $100. Before looking for a leak,  take time to check under the hood. Simply replacing the cabin air filter (located behind the glove box) can fix the air conditioner efficiency. Since the filter catches all the junk you don’t want to breathe, often it’ll clog and block the air flow. A dirty condenser can also prevent the A/C working at its top efficiency.  This is like the outside part of your home air conditioner and get clogged with dead bugs and dirt and grime. You can clean this best using the pressure washer at the car wash.

You can also test the compressor. With the hood up and someone turning on the A/C,  you should hear a click and feel a load  on the engine as the compressor comes on. This will cause the engine idle to go up. If you can locate the pressure switch on the A/C dryer metal canister, unplug it, reconnect it, and retest. If you still can’t figure out why your A/C won’t work, take it to an auto shop. It’s better to seek help and pay for service than potentially damage your vehicle.

Last Updated: June 13, 2016