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How to test radiator fan

Checking the electric fan with an ECU Peugeot & Citroen (PSA) on the car using diagnostic adapters.


For fans with an electronic control unit (ECU) forget such concepts as: first, second and third speed, even in spite of what is indicated in the diagnostic programs. In fans with an ECU there can be more than 100 speeds, since the speed is set proportionally to the pulse PWM signal on the control wire, which can have multiple meanings. By smoothly changing the PWM control signal, you can also smoothly change the fan speed, just as the volume control smoothly changes the volume of the sound. You do not say that you have 2 or 3 volumes in the radio. Such concept as the first, second, third speed can only be used for fans without an ECU, in which the speed is limited by powerful limiting resistors connected to the electric motor using a relay. Or multi-brush motors can be used instead of resistors, in which relays are also responsible for switching various brushes. Let’s say we have a fan without an ECU with one resistor and two relays. We can say about this fan that it has two speeds, each speed is responsible for a separate relay. For the first speed a relay is activated, that connects the electric motor with the resistor. For example, at the first speed the fan consumes 15 amperes with an impeller at 12 volts. When the second speed is activated, the second relay is turned on, which supplies power directly to the motor and it gives maximum speed, for example, 30 Amperes with an impeller at 12 Volts. If a fan without an ECU has 2 resistors and 3 relays, then we can say it has 3 speeds. But in no case is it correct to say that a fan with an ECU has 2 or 3 speeds. The fact that different speeds are indicated in diagnostic programs is ‘echoes of the past’ incorrectly interpreted by diagnosticians. If, for example, we run in the diagnostic program ‘Speed of the electric fan 2’ and connect the oscilloscope to the control wire then we will see that the control signal changes very smoothly and the fan speed also increases smoothly from minimum to maximum speed without any sharp changes.

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Peugeot-Citroen cooling fan replacement (Polish fan)

Yesterday we got a non-working ‘Polish’ fan, which worked only one season and its ‘smart’ brains finally died. We installed ours and the fan started working!

Overview of the “Polish” fan for the PSA.

This is a new fan for PSA, which is made by Poles, as an alternative to the original fan.

The price is lower than the original fan has, but do not be deceived:

  • Firstly, the power of the original, with the same ECU, is 700 watts (50A x 14V) and the power of the ‘Polish’ is only 420 watts (30A x 14V), that is only 60% of the required power. So the ‘Polish’ fan at maximum speed will give out only 60% of the required power. These 40% missing may be the reason for not enough cooling of the engine radiator or air conditioner in hot weather, especially in a traffic jam.
  • In the ‘Polish’ fan the motor is made with sufficient quality, there are 2 ball bearings. But what they finally miscalculated is the electronic control unit (‘brains’). Despite the fact that the ‘Polish’ motor consumes only 30 Amperes instead of 50 Amperes as the original one (at maximum speed with the impeller), the control unit of the ‘Polish’ fan ‘died’ after only one season of operation.
  • In the ‘Polish’ fan a very low-quality solder is used for desoldering the elements. When trying to remove the faulty ECU, a little pressure was put on the connector and it immediately pulled away from the board leaving ‘torn’ marks in the soldering place.

In any case, our ECUs are cheaper than the ‘Polish’ fans and you still have the original fan with a capacity of 700 watts with a 1 year warranty.

Conclusion: The cheap new ‘Polish’ fan is not a worthy competitor for our ECUs.