Radiator fan repair, courtesy of Vortex, here and UK-MKIV forum

[Breezy_Pete]

Having recently discovered that both our VAG stable 'mature' cars (Mk1 Fabia 2005 and 9N Polo 2003) had low speed radiator fan failure, I came across useful online info - here and beyond - to fix them cheaply and relatively easily.

It started from some handy links to a posting on Vortex (see post #3), supplied by del-gti in the Fabia Mk1 forum in a thread started by Dazza95.

 

While sorting out my Polo which had this fault, I came across another fault with the smaller, AC fan, which was running, but weakly (slowly and seemingly 'unevenly'). The equivalent fan on the Fabia was much more energetic and smoother-running.

It turned out to be the case that two of the four brushes in the brushpack within the fan had got stuck in their holders, and were no longer making any contact with the commutator.  This was fixed simply by manually freeing them up and cleaning away the grime and debris that had built up on and around the brushes. Getting into the metal housing of the fan is the only slightly tricky aspect of this, a little brutality required. 

 

This thread from UK-MKIVs forum shows the general idea of the low-speed repair (slight variations will be necessary on the mechanical mounting from model to model).

 

Interestingly, in the first photo of that thread, two of the OP's brushes (the upper two, apparently shorter ones) may be stuck in their holders. Notice the witness marks on the lower two showing where they were prior to being pulled away from the commutator. and how far they've sprung out when removed. All four should have done that.

 

Worth noting that on both of the cars I've fixed, the smaller, so-called AC fan is only single speed, so that won't fail in the way that can be fixed by an external resistor.  Only two wires coming out of the fan motor is the giveaway that it's single speed (even though the loom wiring in both cases had three wires going to the mating connector).

 

FWIW I measured the currents going to the two fans, post repair and found that the main fan (nominal 60W on low speed) took 4.5 amps, the AC fan (90W nom.) took 7A. Seemed roughly in line with expectations given the wattage ratings.

 

Hope this is useful to a few folk as A/C season must be coming soon, right?!

 

 

Edited 30 June, 2016 by Wino

[skoda5232]

Oops

Edited 14 February, 2019 by skoda5232

[Breezy_Pete]

I repaired another radiator fan in which the low speed wasn't working a couple of weeks ago.  From a 2005 9N3 Polo, with just the one radiator fan, and doubly unfortunately the full speed wasn't working either because the relevant wire for that at the radiator thermoswitch was broken.

 

I dismantled the fan motor to check what the failure was, and it wasn't actually the low speed resistor itself, but the (crimped) connection at one end of it which had burned out to the extent that there was no conduction through it.  This isn't an easy disassembly, so if putting 12V between the relevant two pins of the three-way connector doesn't spin up the fan at low speed, it's probably a fair assumption that the same or similar has happened inside yours, especially if the high speed does work.

 

I tried to think of ways to repair the connection, but knowing how hot it was likely to get in there, and with no suitable PTFE insulated wire or crimping method available I decided to put an external resistor in place, as I've done one on two others. Reassembled the motor after checking there was plenty of meat left on the brushes.

 

Minimalist installation this time,  1 Ohm 100W resistor (<£10 from RS or wherever) cable tied to one of the fan legs, cut and spliced some wires, heatshrinking joints with adhesive lined heatshrink, bit of tape to keep things in place (will have to replace neater with black tape soon, the white offends me).

 

 

Method:

• Identify the wire that feeds the low speed operation, pin 2 on my car, red with white stripe; pin 3 is brown/earth; pin 1 is the red/black the high speed connection
• Cut it near to where it goes into the fan motor housing (point A above), pull the wire back completely out of the insulation tubing towards the connector
• Insulate the fan end of the cut, just for tidiness (near letter A above)
• Trim the length down a bit and solder it to one end of the resistor (point B above), weatherproof carefully with heatshrink (adhesive lined preferably)
• Cut the high speed wire close to where it comes out of the connector, give yourself a few centimetres to play with. Pull the rest through to the fan motor end
• Solder a new, plenty-thick-enough wire to the short end of what you've just cut (at point D above). I used some 4mm² white wire I found kicking about in the shed. Weatherproof the joint with heatshrink.
• Thread that new wire up through the PVC insulation towards the fan motor
• Shorten the longer piece of the cut full-speed wire (red/black on mine) so it loops round nicely from point A to point C.  
• Solder it, and the new wire you've added (the white one here) to the right hand end of the resistor (point C above), insulating and weatherproofing again thoroughly with heatshrink. Probably easiest to twist them together first, tin that thoroughly, slide heatshrink on, then solder this twisted-together pair to the resistor.
• Test and refit to car.
•  

It may seem clumsy to do the cutting and joining as I did it above, but with the wire lengths available, my inability to de-pin the crimps out of the connector, and my desire to be able to easily and fully waterproof the soldered connections made it the easiest way for me.  The resistor doesn't get more than warm***, so I feel that the tyraps should be capable and sufficient of keeping it there, having checked that it sits in a position that doesn't obstruct the fan rotation, or collide with anything in the engine bay. 

If you're not used to soldering thick wires, use plenty of solder, a powerful iron and maybe hold at least one part in a small vice so you don't burn fingers while attempting to tin and then connect the ends of what you're joining. Don't forget to slide your heatshrink on (and away from the heated area) before making the joints!

Pull test firmly once cold, and check that the joints look nicely wetted through with solder. Shrink the heatshrink with a hot air gun.

 

Hope this is useful to a few folk. Any questions, don't be shy.

 

***Edit; this proved to be quite a misleading comment, following some 'soak' testing yesterday. This car hasn't been on the road since the above photo was taken, and the testing I did at the time must have been quite brief, probably with a battery off the car.  In fact, when in that position without any sort of heatsink, it actually gets pretty toasty, well over 100°C.  So the tyrap mounting may well be a bit inadequate, and a plate or other heatsink is advisable.

The resistor won't come to any harm, but stuff that's touching it like the tyraps might embrittle over time and break.  In hindsight, mounting it there 'for the airflow cooling' was probably a bit daft, as any airflow it gets isn't going to be cool at all, on arrival.

 

The previous cars I've put resistors on have main fans rated at 60W for their low speed, this one is 90W, I recently discovered, taking approx 7.5A continuous whenever it's running. 

 

An aluminium plate brought the temps down a fair chunk, to around 90°C. I'll add some metal fastenings so that it doesn't rely on tyraps too:

 

Edited 12 June, 2021 by Wino
Further testing

[SuperbTWM]

Nice repair 👍, I can't tell by the photo but is that the heat-shrink that has the glue in it? If not, I highly recommend getting some for added piece of mind, it seals up solder joints really well.

Edited 2 May, 2020 by SuperbTWM

[Breezy_Pete]

Cheers. Yes it is adhesive-lined heatshrink.