From the mid-1990s, most vehicles equipped with air conditioning have equally been outfitted with electronic modules that tell your vehicles’s AC compressor to cycle on and off. Although it may be disturbing the first time it happens at a stoplight or during idling at the store, it is very normal. The electronic module in the car’s air conditioning system is informing your car’s compressor that it can take a break because the car has achieved the interior temperature you have wanted and the compressor is not needed at that moment to move the refrigerant around.
BUILT-IN ECU PROGRAMMING
You will equally notice air conditioner compressor cycling when your car is under hard acceleration, like when you are pulling onto a major freeway. This is part of the programming that is manufactured into the electronic system that takes all extra systems that might get power from an engine under acceleration and get it back to the engine itself. Again, this is a normal operation.
If you do notice that your car’s air conditioner compressor is cycling on and off too often, then it likely shows that your vehicle’s electronic module is failing. Yes, it is easy to blame a mechanical system but your car’s compressor system is engaged by the clutch and that, in turn, is driven by the ECU (electronic control unit) for the air conditioner/heating system.
REASONS FOR FAILURE
Why would a system like this fail? It could be associated to temperature. As systems age, they become more prone to failure, especially heat or cold-related failures. Although it isn’t really advisable to check inside the module, if you could tear the cover off, you would see a bunch of tiny dark chips on the board with numbers on them. Some of these devices are actually resistor packs that will replace value over time depending on the vehicle’s operational environment (engines are not conducive to longevity for many devices because of the heat/cold cycle they run through).
Once a resistor pack (or thermistor—it’s temperature-controlled cousin) changes value, then the ECU signals that are supposed to happen at some points may change, resulting in alteration in your car’s compressor cycles. The solution to this issue is to take your car to a service area where they have the computerized equipment that will tell them the modules that have failed and need change. If you are a bit strapped for cash, you can find an aftermarket change module, purchase a service manual, and try to change it yourself instead. This is only advised if you have at least some experience working with car computer systems or you could cause even more damage.
USE SERVICE AREA
Since it is advisable to let the professional handle this—it is their responsibility to make it work—let your service area take care of changing the module after they’ve identified the issue. They will have the right part on hand and can get you on your way quickly. Best of all, you will not have to think about it as the work is finished and the cycling should have stopped. If not, bring it back and they will have to fix it free of charge