Radiator fan repair (variable speed)

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My Name: Ozvtr

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Posts: 1043
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
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There seems to be a few people with air conditioning and a variable speed radiator fans and who are having problems with said fan.
I came upon this on YouTube.
Unfortunately this might not fix their problem as they might not possess the skills or facilities, but they might see what the problem is and a possible solution.
For most, just replacing the assembly is the answer, but you can see why the units stop working.


https://www.youtube.com/watch?time_cont ... =emb_title

User avatar
My Name: Ozvtr

Moderator
Posts: 1043
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
Has thanked: 44 times
Been thanked: 300 times

Post

I have finally figured out whats what with respect to the variable radiator fan speed controller for Mk1 and MK2 C3's with air conditioning.
fan.jpg
Big black connector. Pin1 white wire. +12volts from battery.
Pin2 green/yellow wire. Ground to chassis.

Small grey connector. Pin1 mauve wire. Fault signal to engine ECU. (0v = fault)
Pin2 yellow wire. PWM signal from engine ECU. (+12, fan off. Ground or open circuit, fan full on. Pulsing, intermediate speed.)
Pin3 grey wire.Ignition on power signal from BSM. (+12V = ignition on)
fan01.jpg
fan01.jpg (234.94 KiB) Viewed 488 times
The fan motor and speed controller are all one unit. There are 5 electrical connections on the unit but only 4 are used in this configuration. Power is connected to the 2 big pins on the fan/controller. Of the 3 remaining small pins only 2 are used. 1 for speed control and 1 to indicate there is a fault with the controller.
If the PWM line is high (+12V), the fan will not run. If the line is low (grounded) or open circuit, the fan will run at full speed. If the PWM line is pulsed between low and high, you will get a variable speed from the fan.
Power to the fan/controller is controlled by a relay which is run by a signal from the BSM. When the ignition is turned on, power to the relay is supplied from the BSM. The relay contacts close and now power is available to the fan/controller.
With just power applied to the fan and no other contacts connected, the fan will run at full speed. The main contacts in the relay failed (shorted out) in my C2 (yes c2) and the fan would run at random times, even in the middle of the night!
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