Many automotive air conditioning failures have underlying mechanical or physical causes. For example, the internal parts in the compressor may fail, leading it to seize up. Leaks are another common issue. Reduced refrigerant pressure will prevent the system from operating correctly, causing the evaporator coils to freeze and the compressor to shut down.
Modern AC systems also rely on numerous electronic components, however, and these can also stop working. Problems with your HVAC system's electronics can sometimes be more challenging to notice, and they can produce more erratic symptoms than other failures. Keep reading to learn about three electronic components that may leave you sweating this summer.
1. Climate Control Units and Related Sensors
Your car's climate control unit is the physical connection between you and your HVAC system. Like the thermostat in your house, the climate control unit in your car gives you control to set your desired temperature, adjust fan speed, and so on. If your vehicle has an automatic climate control system, it also uses sensor data to determine the current interior temperature.
A failed climate control unit or a bad temperature sensor can cause your air conditioner to operate erratically. You may not be able to switch to your desired temperature, or you may find that your automatic climate control blows full-strength cold air even after cooling your cabin. These issues often point to a problem with the electronic hardware in the control unit.
2. Blower Motor Resistors
If you aren't familiar with resistors, they are one of several essential components found in most electronic circuits. The blower motor resistor varies the flow of electricity to your car's blower, allowing you to alter the fan's speed by using the climate control unit in your dash. Automatic climate control systems may also vary the fan speed using this component without your input.
A faulty resistor can cause your fan speed to change wildly or cause the fan to remain pegged at a specific rate regardless of your settings. While resistors are usually relatively cheap components, they sometimes require a significant amount of labor to remove and replace.
A relay is a simple device that takes a small input current and outputs a much larger one. Your air conditioning relay switches on and off to provide power to the compressor, but relays can sometimes fail. The compressor won't receive the input power it needs to switch on when the relay fails, preventing the system from cooling your car.
You can usually hear the AC relay switching on and off if you listen with the hood raised. If you can't hear the relay, it may be failing. In these cases, simply replacing the relay will get your car's air conditioning system pumping cool air back into the cabin again.
Contact a local auto AC repair service to learn more.