How to: Check your cooling system fans

[MMamdouh]

The cooling fans are mounted behind the radiator in the engine compartment. The electric cooling fans increase the flow of air across the radiator fins and across the condenser on air conditioner (A/C)-equipped vehicles. This helps to speed cooling when the vehicle is at idle or moving at low speeds.

The main fan size is 320 mm (12.6 inches) in diameter with five blades to aid the airflow through the radiator and the condenser. An electric motor attached to the radiator support drives the fan.

A/C models have two fans - the main fan, and the auxiliary fan. The auxiliary fan is250 mm (9.8 inches) in diameter. Non-A/C models have only the main fan.

A/C OFF or Non-A/C Model

? The cooling fan(s) are actuated by the powertrain control module (PCM) in vehicles with an automatic transaxle or the engine control module (ECM) using a low-speed cooling fan relay and a high-speed cooling fan relay. On A/C-equipped vehicles, a series/parallel cooling fan relay is also used.

? The PCM or the ECM will turn the cooling fan(s) on at low speed when the coolant temperature reaches 93?C (199?F) and high speed at 97?C (207?F).

? The PCM or the ECM will change the cooling fan(s) from high speed to low speed at 94?C (201?F) and turn the cooling fans off at 90?C (194?F).
A/C ON

The PCM or the ECM will turn the cooling fans on at low speed when the A/C system is on. The PCM or the ECM will change to high speed when the coolant temperature reaches 115?C (239?F) or high-side A/C pressure reaches 1882 kPa (273 psi).

The cooling fans will return to low speed when the coolant temperature reaches 112?C (234?F) and high-side A/C pressure reaches 1448 kPa (210 psi).

Engine Cooling Fan Circuit Check - With A/C

Circuit Description

The engine cooling fan circuit operates the main cooling fan and the auxiliary cooling fan. The cooling fans are controlled by the powertrain control module (PCM)/engine control module (ECM) based on inputs from the engine coolant temperature (ECT) sensor and the air conditioning pressure (ACP) sensor.

The PCM/ECM controls the low speed cooling fan operation by internally grounding the PCM/ECM connector terminal C13. This energizes the low speed cooling fan relay and operates the main cooling fan and the auxiliary cooling fan at low speed as the cooling fans are connected in a series circuit.

The PCM/ECM controls the high speed cooling fan operation by internally grounding the PCM/ECM connector terminal C13 and the PCM/ECM connector terminal C12 at the same time. This energizes the low speed cooling fan relay, the high speed cooling fan relay, and the series/parallel cooling fan relay resulting in high speed fan operation as the cooling fans are now connected in a parallel circuit.

Diagnostic Aids

? If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the engine coolant temperature gauge indicated overheating. If the engine is overheating and the cooling fans are on, the cooling system should be checked.

? If the engine fuse block fuses EF4 become open (blown) immediately after installation, inspect for a short to ground in the WI ring of the appropriate circuit. If the fuses become open (blown) when the cooling fans are to be turned on by the PCM/ECM, suspect a faulty cooling fan motor.

? The PCM/ECM will turn the cooling fans on at low speed when the coolant temperature is 97 ?C (207 ?F) . The PCM/ECM will turn the cooling fans off when the coolant temperature is 94 ?C (201 ?F) .

? The PCM/ECM will turn the cooling fans on at high speed when the coolant temperature is 101 ?C (214 ?F) . The PCM/ECM will change the cooling fans from high speed to low speed when the coolant temperature is 98 ?C (208 ?F) .

? The PCM/ECM will turn the cooling fans on at low speed when the A/C system is on. The PCM/ECM will change the cooling fans from low speed to high speed when the high side A/C pressure is 1882 kPa (273 psi ) then return to low speed when the high side A/C pressure is 1448 kPa (210 psi ). When the A/C system is on, the PCM/ECM will change the cooling fans from low to high speed when the coolant temperature reaches 117 ?C (244 ?F) then return to low speed when the coolant temperature reaches 114 ?C (237 ?F) .

? The cooling fan circuit can be checked quickly by disconnecting the PCM/ECM connector 2 and grounding the connector terminal C13. This should create low speed cooling fan operation with the ignition ON . By grounding the PCM/ECM connector terminals C13 and C12 and turning the ignition ON , high speed cooling fan operation should be achieved.

MMamdouh