Radiator fan always running - how to repair

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My Name: Chapster

Posts: 14
Joined: Mon Mar 30, 2015 9:11 am
Model: C3 2002-2005, Original shape model
Year: 2002 (52)
Engine Size: 1.4 (8v)
Fuel Type: Diesel
Mileage: 124300
Trim Level: Touch
Gearbox: Manual 5 speed



When I bought my C3, I found the radiator fan had been unplugged. I plugged it back in to find it ran continuously. eBay seems to do a relatively cheap replacement, but if you're on a very tight budget like me, then here's how to fix it (apologies about the lack of photos, but I hadn't intended on doing a write-up at the time):

Remove the fan assembly from the vehicle, then the fan itself. Remove the fan blades. It is necessary to remove rear portion of the fan motor to reveal the PCB covered in silicone and the brushes (it's the part where the electrical connector plugs in).

Here's a pic with the silicone removed, just to show the part you need to be working with:
To remove it, I used a dremel cutting disc to remove the top tags that have the edges squashed out, holding it to the motor body.

Unfortunately, the entire PCB has been coated with a thick layer of silicone. I hacked most of it away in order to do checks on the components. To fix yours, it is only necessary to remove the silicone over this MOSFET transistor:
I used a screwdriver to remove the silicone and was very careful not to damage the PCB. The cause of the fault is a short-circuit MOSFET transistor, it most probably fails from heat as it passes a lot of current. I ordered a replacement from eBay. The part required is a FDB8441 eBay link.

Unsoldering the old one is easy enough with a soldering iron of a high enough wattage (I use a 50W Weller), and installing the new one is easy too. Afterwards, I used windscreen sealant to coat the area for waterproofing.

Place the repaired rear cover back onto the motor body, being careful with the brushes, helping them over the commutator. You can either put some little tack welds on top of the tags that were ground off, or you can drill with a tiny drill bit and put some self-tapping screws in, which is what I did.

Now works perfectly and passed the Lexia test.

Hope this helps someone.
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My Name: C3CAR

Posts: 2661
Joined: Wed May 04, 2011 10:01 am
Model: C3 2002-2005, Original shape model
Year: 2002 (02)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 140000
Trim Level: Exclusive
Gearbox: Manual 5 speed
Engine name: DV4 16-valve diesel (90 PS)
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Been thanked: 93 times


Great work Chapster,

Those brushes have plenty of meat left on them so I can see its well worth repairing the board. Worn brushes can be replaced but a worn commutator will probably need a new fan assembly.
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