Troubleshooting Common Condenser Fan Problems

How the Condenser Fan Works

Some older vehicles have a single electric condenser fan, which only energizes with the air conditioning compressor, while engine cooling is provided by a belt-driven thermostatic clutch radiator fan. Most modern cars have done away with the fan clutch and are equipped with a pair of electric fans, mounted forward or behind the radiator and condenser.

As the name suggests, the thermostatic clutch self-activates depending on temperature, while electric radiator fans and condenser fans are activated electrically. Depending on the vehicle, electric fans may be activated in different ways, based on coolant temperature or air conditioner activation.

• Temperature Activation: Some electric fans are activated by an engine coolant temperature (ECT) sensor or switch, though not the same ECT the engine control module (ECM) uses for other calculations, like fuel injector pulse width. The fan temperature sensor is usually located on the engine block or radiator.
• Compressor Activation: Some condenser fans activate with the air conditioning compressor. When the compressor cycles on, it also feeds a line to the condenser fan relay, running the fan.
• Fan Selection: Depending on vehicle design, the fans may operate singly or in tandem. Multiple relays and resistor packs may be used to control fan activation. On some vehicles, for example, only the condenser fan operates with the air conditioner, while only the radiator fan operates based on engine temperature. On other vehicles, both fans can be activated by either air conditioning or engine temperature.
• Fan Speed: Depending on the situation, more or less air flow may be required. To run the fans at low speed, the relays route power through them in series or through resistor blocks. When high speed is needed, such as at a certain temperature threshold or with the air conditioning compressor, relays route power to the fans in parallel or bypass the resistor blocks.

Common Condenser Fan Problems

If you notice diminished air conditioning response, hear unusual noises, or the engine overheats at a stop, you may have a radiator fan problem. Consult the repair manual for your specific YMME (year, make, model, engine) for details on exactly how they are activated. This can help you diagnose some of these common condenser fan problems.

• Fuses and Relays: On any electrical problem, the first thing to check is for power problems, starting with the fuses, relays, and wiring. Before replacing a blown fuse, test the system for short circuits, using a multimeter. Relays can often be checked by swapping with a known-good component relay, such as from the horn or ABS (anti-lock brake system).
• Temperature Sensor: If the temperature sensor is faulty, it won’t activate the fan. You can usually test for switch functionality by unplugging the sensor and putting a jumper wire across the connector. If the fan comes on, this means the sensor may be faulty. Double-check resistance or continuity compared to actual temperature, with a multimeter and thermometer or OBD scan tool, to be sure.
• Coolant Level: Logically, if the temperature sensor isn’t submerged in coolant, such as an air pocket or low coolant level, it can’t detect coolant temperature. Look for leaks and check and adjust coolant level.
• Resistor Problems: Some vehicles use a fan resistor pack to enable different fan speeds or activation levels. This is easily checked, as well, by disconnecting it and testing with a multimeter. Check the resistances according to the repair manual, and a general rule of thumb is any open circuit fails the test, reading ∞ Ω or OL Ω (over limit).
• Motor Problems: A motor short-circuit or open-circuit will prevent it from running. A blown fuse is a good indicator of a short-circuited motor. The easiest way to check this is to disconnect the fan and check for resistance across the terminals. If the multimeter reads 0 Ω, ∞ Ω, or OL Ω, the motor will need to be replaced.
• Fan Problems: Unusual noises are a good indication there is a problem with the fan itself. If it’s scraping, wobbling, or grinding, it could indicate that the fan motor and fan blades are no longer connected.

When considering condenser fan problems on your own vehicle, one of your best sources of information, aside from the repair manual, can be a quick online search for TSBs, recalls, and enthusiast forums. Of course, no search engine result should be mistaken for a diagnosis, but when many vehicles share common problems, this can shorten diagnostic time and effort by pointing you in a common direction.If testing the suggested component doesn’t result in a fix, check the rest of the system and ask a local trusted mechanic for advice.