Hurrah for car tripsexcept put on the air conditioning. And when you go to turn on this glorious relief from the hot, sticky weather, it doesn't work. Uh oh. You better be prepared for a KDDO. Even if the air started coming out in those nasty hot spurts that smell like rotten eggs, at least you know there was some hope it might cool off when the toxic Freon kicked in. You're wondering why your system isn't working and it could easily be your A/C's relay switch.
Relays are electronic switches that often transmit signals between contactors and circuits. Air conditioning relays, also known as fan relays, control both the actual fan and the A/C clutch. They work by acting as control switches that either allow or prevent the flow of air. They are initiated by pressing the buttons and settings on your car's A/C. Once you set the temperature and the power, the relay will send the signals to the fan. The fan will then operate in bursts depending on these settings.
Location and Purpose
The A/C clutch relay is connected by a wire to the compressor. It transfers the energy from the control board to the compressor. The compressor then pressurizes the refrigerant so you can get cool air, not just air. It's sort of like a "middle man" but without it, you're not going to get the cooling you need while you drive. A fan relay sends the signal for the fan to push the air through the ventilation system, depending on the frequency and temperature you desire. Many of them will be 12 volt. That should be sufficient for your vehicle.
How to Test a Relay
* The car must be turned on to test a relay because it has to be powered. Most car relays will be connected through wiring to the car's battery, whether it's a direct line or through the system.
* If you can, take the power wire from the relay and connect it to a power tester or test light. If it's a positive reaction it's not the power source causing the problem and the relay should be working.
* Turn off the car and unplug your relay. Test it with an ohmmeter. An ohmmeter measures the resistance of an electrical current. Too much resistance will make the meter's needle veer left. No resistance will make the meter stay at 0.
* If the relay is not workingthen you'll probably have to jumpstart it or replace it. In order to jumpstart your relay, you need to connect the relay circuit to a battery and a ground source. If there's no click it needs to be replaced.
