VW Golf/Jetta/Bora MKIV Fan Problem- Diagnosis & Repair from UK-MKIVs.net



Problems with your fans : READ ALL OF THIS then comment...


ANDYMAC: Right I will explain this only once as I have explained it SOOOO many times over the last year

Basically all cars with Climatronic have 2 fans and each fan has 2 speeds, slow and fast.

When the air con is on the fans are meant to turn at a consistent low speed and if the engine gets hot they will run at the higher speed, but what is happening to almost all fans is that the low speed resistor within the fans is burning out so the fans will only pulse to high speed which isnít really adequate for cooling the engine in warm weather, another consequence is that the high speed fuse blows and you are left with no fans and overheat and bugger your engine.


I have so far disassembled 3 sets of fans and all had the same problem, which was the low speed resistor, the fans are a sealed unit so cannot be easily repaired, VW charge £90 + VAT for these EACH and £200 labour for fitment, so basically you have £400 consumables on your car that need replacing every 30000 miles, which in my eyes is very very wrong, if nothing else they should be supplying them on an exchange basis as per the MAF as it is such a widespread problem, I have even heard of R32's with the problem now.†† I fI can get enough support on here plus one or 2 people who have had a run in with VW about this then I am going to approach watchdog as it is disgraceful that VW are profiteering of a known engineering problem on one of the models.


ANDYMAC:I looked at over six 4motions last year for my mate, and every single one had this problem, I would hazard a guess that many R32's are now having this problem as well, however it does affect all models I think not just V6ers and V5ers


ANDYMAC:right I need to clarify this as some people arenít getting this

1. Turn engine on,

2. Turn aircon on,

3. Make sure ECON is "OFF"

4. Check fans are running constantly IE for more than 1-2 minutes

5. If the fans do nothing then run very fast, then stop after a minute or 2 or even 3 then you have faulty fans


BIGAL: The radiator fans are controlled by a two stage thermostatic switch, the first switch closes at approx 85 degC and switches on the low speed fan and the second closes at approx 95degCand runs the fans at full speed. I assume this two speed arrangement is to keep noise levels down, as the fans never need to run at full speed under normal circumstances.

They come on low speed when the aircon is on, to cool the aircon compressor which is mounted directly behind them.


BARON VON MARLON/RF STEEL: Baron Von Marlon - If you've had your fans replaced once already, they should still be under the 24 month warranty that comes with the replacement !!

VW Replacement Parts- All genuine Volkswagen replacement parts purchased on or after 01/11/01 carry a warranty for a minimum period of 24 months, with no mileage limitation, from the date of purchase. Parts replaced within the warranty period for passenger cars are covered for the balance of the 3-year period. After this period, replacement parts carry the 24-month warranty referred to above. Other items with warranties in excess of 24 months will be advised to you at the time of purchase. This does not apply to parts fitted under the terms of the vehicle warranty, which are warranted for the remaining period of that warranty.



ANDYMAC:Original Fan Autopsy here http://www.uk-mkivs.net/forums/17772/ShowPost.aspx - Do not use fix shown here it doesnít last long!!!


BIGAL: My fix is more straightforward, it only involves mounting two resistors on to a metal plate and splicing into the fan wiring. It does not involve any disassembly of the car (especially the fans) and does not damage the cars wiring loom. The only hassle is making the metal heat sink plate; it is only approx 30 mins work for anyone with simple metalworking tools. I have drawn up the heat sink and can email the drawing to anyone interested.


BIGAL: From Thread http://www.uk-mkivs.net/forums/50268/ShowPost.aspx

I checked my V5's cooling fans today and they are no longer running on the low speed. I've disconnected them and checked the fans by themselves and the internal resistors are burnt out on both fans.

I have reread the posts by Andymac and others about this problem and I have decided to fit external resistors to repair the low speed function.

From Andymac's previous posts it looks as if the resistor for the bigger of the two fans is approx 0.8ohm.

I have just tried a 1 ohm high power resistor in series with each fan and measured a current of 7.0A (with engine running) for the big fan and 5.5A for the small fan. This means that the big fan will need a minimum of a 50W resistor and the small fan a 30W resistor.

My question is, has anyone actually measured the low speed current drawn by each of the fans when running with the internal (unbroken) resistor? If not does anyone know the internal resistor values for both sizes of fan?

I will publish details of this mod when I have finished it.


JONJON/ANDYMAC:Quote: posted by JonJon on 09/04/2005 19:46:12

Iím also interested in this as my slow speed fans are not working.

it's not causing any bother though as the temp needle never moves over the 90 mark, even if I just let it idle until the high speed fans cut in, is this normal(in a broken sort of sense)i.e. what temp is the fast cut in supposed to be?

BigAl- if it's not too much bother could you explain how you tested the low speed supply to the fans so I can check mine.

The temp needle is very inaccurate! believe me the car will be running at higher than 90, the other problem is when you get stuck in traffic on a hot day the high speed will blow a fuse then you will be left with no fans and you WILL overheat. PPS no low speed will also bugger the aircon compressor and lead to a £1000 bill, (Ask RFSTEEL)if you donít fix it soon at least take the following precautions carry a spare fuse with and the tools to change it and run the Climatronic only in ECON mode.


BIGAL: (The fix) I have been setting up my web space to host this guide, hopefully it will be finished shortly, and it will be viewable at http://website.lineone.net/~alan.james.lorely

Andy, both resistors are on one heat sink which is mounted under the passenger side headlamp. It is not in the fan airflow and doesn't need to be provided the heat sink is the same or larger than mine. I tapped into the wiring on the fan side of the wiring, this means if anyone wants to replace the fans later and remove the mod then the cars wiring is undamaged.


BIGAL:†††††† The failure of the fans low speed does not directly damage the engine, but the constant high speed pulsing of the fans does eventually blow the main fuse and then engine overheating could occur, which if ignored would lead to engine damage.

The air con compressor is mounted directly behind the smaller fan in the airflow and I believe that this is to cool the compressor, presumably lack of cooling damages the compressor.


TIW30: Just finished my resistor mod (Thanks to Big Al for all the research) and both fans are now working perfectly all for £15 great the mod is quite straight forward if a little fiddly to do in some places, and anyone doing it in a 150 TDI will need to remove the front intercooler pipe to get access to the plugs


BIGAL FIX: http://website.lineone.net/~alan.james.lorely/fan%20mod/Repair.html or HERE


Dsgwagen: (numpty) A lot of the time problems with the fans are caused by the control unit, if you change the fans and the control unit is faulty they will go again.


ANDYMAC: Itís got nothing to do with the control unit, if it was how come 03 r32's with the r32's are suffering the same problem.

Dsgwagen do you care to explain where and how the control unit creates a problem?Have you read the whole of this thread? Have looked at the links or worked out the current calculations that the thermal resistors within the fans have to control? How many fans and control units have you replaced or disassembled?

I am asking this as at the end of 10 pages of thread and investigation by myself and a few others such as BigAl you jump on and say itís the control unit? I just want to know on what evidence you base this on.


NUMPTY: I was under the impression that the control unit fails causing the fans to get stuck on fast blowing them out usually taking the 40a fuse with them. I can't really be bothered to read the thread or the 10 elsewhere but Iím just pointing out that a lot of control units get sold, maybe for a different fault to the one you are highlighting but still.



ANDYMAC: Well if you canít be bothered then donít clutter the thread with untruths, and uninformed advice, I already spend half my time reassuring people that ITS NOT THE CONTROL UNIT mostly because people like you DONT READ THE EVIDENCE AND ASSUME ITS SOMETHING ELSE




DSGWAGEN: I was told that when this problem first came about that they were just changing fans and they were going again, but now they change the lot 2x fans 1x ecru and the fuse and they don't get any comebacks now.


EVILHOMER: Dealers LIE!!!! lol



I have done the resistor mod and it works fine, however you do need a fairly substantial piece of aluminum as they do get exceptionally hot (Still going 10000 miles on)


GREENBEAST: right...I got my fans working again

I implore anybody about to undertake this mod to check the green fuses on top of the battery and clean them up so they are free of corrosion

my father-in-law-to-be and I only discovered they were corroded AFTER we had fitted the whole resistor modification

so after the fuses were cleaned up it all works and we've reconnected all the wires how they originally were

only good thing is that I have a ready made resistor mod for if/when the fans do go properly!


ROYR32:My R32 went in for warranty work and we asked them to check the fan as it only comes on high speed for 3 - 4 seconds.When we picked it up the man told us that they had spoken to VW and they said it was within acceptable parameters.It did it in front of a couple of the "technicians" and we told them that were what we talking about.I said I could not see that it could do anything during that short period.He said it does, because it is such a high speed fan it only needs that long! Is this faulty or could he be telling the truth?


ANDYMAC:††††† I can confirm that your fans have failed, and Roy read the whole thread and realize that yours have failed and dealers are liars and are stupid



I did the external resistor mod last weekend and they work a treat.

A mate in the metal industry, laser cut a piece of 3mm ali using the template on Big Al's site.I followed all the instructions on his site so thanks a lot Big Al, you saved me a fortune and the template was spot on.

This shape fits fine on V5, V6 cars (thatís what Big Al had) and I have a 150tdi so assume it would fit all the TDIs.

If anyone wants a plate laser cutting then I can get them for £13 each, but the minimum order is 10 pieces.If anyone wants one then send me a pm or maybe reply here, I could set up a group buy if enough interest.I am not making any profit on this, its cost so if anyone can get it done cheaper then thatís cool.

Hopefully there should be a pic attached.







First the fans themselves.

Disconnect the fan connector and measure, with a multimeter, the resistance between the red/white wire and the brown wire, it should be a value less than 10ohms, a much higher value indicates a burnt out internal resistor. Next measure the resistance between the red/black wire and the brown wire it should also be a value less than 10 ohms, a much higher value indicates a burnt out fan.


Next the fan controller, fuses etc.


The test detailed is taken from the VW repair manual for the V5.

Caution keep hands etc away from the fans during this test as they are expected to run:


Reconnect both fan connectors, if still disconnected, and disconnect the 3 pin connector from the radiator fan thermo switch.

Bridge contact 1 and contact 2 with a short piece of wire, the fans should run at low speed.

Switch on ignition, bridge contact 2 and contact 3 with a short piece of wire, the fans should run at high speed.

Switch off ignition, reconnect thermo switch connector.


To identify the connector pin numbers, hold the connector facing you with connector latching mechanism at 2 o'clock, pin1 is then at 12 o'clock, pin 2 at 4 o'clock and pin 3 at 8 o'clock.


For anyone who wishes to try to test the thermo switch, low speed is switched on between 92 and 97 degC and the high speed switches between 99 and 105 degC.


ADDED (NEW FANS 15/May/2006)


The newer fans will fail some guys on here have been through 4 sets ... even some of the last R32's on 54 plates have had fans fail...... the most common PM I get is will the modded fans ... my answer is yes but not quite as quickly as the originals, I have seen some original fans fail in 15k and modified ones fail by 40k but this hard to verify as it is hard to know if they were fitted from new... but they still failed.


The reason they will fail is a design fault of VW all other cars from the big Audis down to the Passatswith Climatronic, use a fan speed controller, that utilizes "pulse width modulation" to control the fans and thus negates the need for resistors in a high current circuit. (I have been told this by several reliable sources but donít know if itís the gospel truth)



Now should you fit them? well my opinion is this

if its warranty job yes, as it keeps the car omen (but inferior LOL) but costs VW in the region of £500... serves 'em right

if its not warranty, well itís your choice £400 for something inferior that will fail half as fast as a clutch! or £15 and 2 hours work for a fix that will outlast the car!!!!



THATíS ALL FOLKS....... the longest synopsis ever.... but it should stop any stupid questions about fans or is it really the fan.