Engine overheating or poor air conditioning performance is usually due to an engine or A/C condenser cooling fan that fails to come on. In many instances, the underlying fault is actually a negative cooling fan relay.

The quickest way to tell irrespective of whether or not the electrical fan(s) are functioning is always to start the engine, allow it attain standard operating temperature and after that turn the A/C on. The cooling fan inside the engine compartment must turn on to pull air from the radiator and A/C condenser. On a lot of autos, there may very well be two fans: a key cooling fan for the radiator, along with a second fan for the condenser. Each supporters ought to come on once the A/C is on.

If one or each fans fail to come on, the lack of added cooling offered by the fan may well result in poor A/C cooling overall performance, and it might bring about the A/C compressor to overheat and fail. The engine may also run hot and overheat, also.

Complications during the Cooling Fan Circuit
The standard electric cooling fan circuit involves a temperature sensor, a relay, a manage module as well as the fan motor. The relay would be the part that fails most usually, so be sure you check the relay in addition to its power supply and ground connections.

A good relay coil will typically read 40 to 80 ohms. If resistance is large, the coil may well still be operating but it is failing, or it may not get the job done when electrical loads are high. If the coil has no resistance, it truly is open and possesses failed. Substitute the relay.

Another simple relay check should be to shake it. Should you hear something rattling inside, the relay armature is most likely broken.

Forms of Electric Cooling Fan Relays
You will find three simple varieties of relays:

Generally open will be the most common form. The armature closes when the coil is energized to route power on the fan motor.

Commonly closed. The armature is usually closed and is pulled open when energized.

Dual relay. This type conducts latest when open and when closed in two distinct circuits.

Some Cars with Cooling Fan Challenges

Chrysler minivans (late 1980s and early 1990s). These use a solid state relay for the cooling followers, plus the relays have a tendency to overheat and fail.

Chrysler Neon. The situation right here may be the cooling fan circuit employs a radio frequency filter mounted on radiator fan shroud. The filter is mounted within a hot place and tends to fail, preventing the cooling fan from operating.

On most Chrysler cars, the cooling fan relay need to be engaged ahead of power can visit the A/C clutch. In case the fan relay has failed, it can protect against the compressor clutch from engaging and there will likely be no cooling.

Ford cooling fan controllers (late 1980s and early 1990s Mustangs and other models). The controller consists of a fan primary relay, A/C fan management relay, and wide open throttle cutout all developed into one unit. The controller is supposed to switch on both followers if the compressor clutch is engaged. The problem is the two fan motors pull so much amperage that they rob voltage from the clutch. Consequently, the compressor clutch may perhaps only get 9.8 volts as an alternative of complete battery voltage triggering it to slip, overheat and fail. The remedy right here is usually to add a separate relay for that compressor clutch so the clutch can draw full voltage in the battery.

Ford integrated relay management module (IRCM) (introduced in 1986). This unit controls the each fan relays, compressor clutch relay as well as fuel pump relay. The module is mounted about the radiator shroud and is exposed to a great deal of heat so failures are widespread. One symptom right here of the failed module can be a car that cranks but will not start as the fuel pump isn’t finding any power by its relay. A failed module may also reduce one or the two supporters from operating, or the compressor clutch from engaging. The IRCM module also delivers two-speed (high and very low) fan operation by using an internal resistor to drop voltage to the followers. This resistor typically burns up and fails. If any on the subsystems within the IRCM module have failed, the entire module should be replaced.

Chrysler LH cars (since early 1990s). These automobiles use two relays (very low fan and substantial fan), and two fans. Three fuses during the power distribution box guard these circuits. The engine management module gives ground towards the fan relays when cooling is required, as well as a dropping resistor is positioned within every single fan motor for two-speed operation (that is why just about every motor has two power input terminals but only one ground terminal). At 238 degrees F, the fan relay switches power from the low-speed circuit to your high-speed circuit to boost cooling. If this relay fails (which it generally does as a result of the load it carries), the fan may well operate at high speed but not reduced speed. Other inputs that will affect once the fan relays are energized include engine temperature, transmission temperature, intake air temperature and A/C operating pressure. On this car, it is best to use a scan instrument to find out which of those inputs is energizing the supporters and when.

If a compressor clutch on any vehicle has failed, the cause may be reduced voltage to your clutch. Very low voltage permits the clutch to slip, which results in excessive friction and heat. Use a voltmeter to measure voltage towards the clutch. If it is not within 0.2 volts of battery voltage, other parts inside the circuit can be stealing power in the clutch. The cure could possibly be to demand the clutch circuit by including a brand new relay so the clutch will surely have its very own focused power circuit.

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