C5 coolant fan

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Danbj
Posts: 6
Joined: 06 Jun 2021, 16:20

C5 coolant fan

Post by Danbj »

Hi all,
Emboldened by my success with my wipers, I thought I would tackle the faulty radiator fan on my son's x7.
Vin VF7**************[VIN obfuscated, can be read by forum staff]
Diagbox suggests a fault to ground, with fan assembly and speed control codes. I have removed the bumper and discovered after much head scratching a broken wire leading to the fan speed sensor. I have replaced this wire thinking problem solved. No improvement. I have bench tested the relay and it clicks and continuity is achieved across the appropriate pins. I have bench tested the fan and it spins up if I give it 12v. I have put a meter across the fan pins and I am not getting any resistance that might indicate a short internally. Maxi fuse is ok. All accessible wiring seems ok now, so should I just bite the bullet and buy a new fan or am I missing something?
Happy Easter Dan
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GiveMeABreak
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Joined: 15 Sep 2015, 19:38
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Re: C5 coolant fan

Post by GiveMeABreak »

The fan assembly control is in a remote location in the electrical harness, so not sure if this may be where the issue is. I have no further detail where though.
x7 fan.PNG
(1) Fan .
(2) Fan blade.
"a" 2-way black connector (Supply).
"b"3-way grey connector (Part of control).

Allocation of the channels of the black 2 -way connector
Channel NumberDesignation
1Supply to the fan unit
2Earth

Allocation of the channels of the grey 3 -way connector
Channel NumberDesignation
1Control of the fan assembly
2Cooling fan diagnostic information
3Power supply to the fan assembly module
Please Don't PM Me For Technical Help

Marc
Danbj
Posts: 6
Joined: 06 Jun 2021, 16:20

Re: C5 coolant fan

Post by Danbj »

Thanks.
I found the control module, mounted on the wing to the right of the battery. I swapped it out with the one in my x7. (Its handy having a donor for testing!) But the short to earth is still present. Both speed control modules work in the donor car. I have inspected all wiring I can see and tested continuity where I can but am stumped. I suspect the fan motor although it works on the bench. I'm not prepared to strip the bumper off the other car so off to fleabay again!
Thanks Dan
Estately
(Donor 2022)
Posts: 191
Joined: 02 Nov 2010, 21:50
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Re: C5 coolant fan

Post by Estately »

If it is any consolation I had a similar problem with the fan on a 57 plate MKII C5 with loads of miles.
Spun up beautifully with 12v on the bench but on the car nothing.

So fleabay and Poland to the rescue, just plugged new fan in and no further problems.
Would Love to know what went wrong.

Hope that helps.
Andy.
If it can happen it will.
Danbj
Posts: 6
Joined: 06 Jun 2021, 16:20

Re: C5 coolant fan

Post by Danbj »

Hi Andy
That's reassuring. I have convinced myself that its the fan at fault by using diagbox. With fan connected it reports short to ground with fan disconnected open circuit. On the bench it spins, but obviously its not easy to check for short across the sensor wires whist powered up. I am guessing the short only occurs when the motor is energized. Thank you for your input.
Kind regards Dan