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Fabia 2 (2010) ---- Fan resistor pack failure .... a saga ......


nigech

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Hi,  I've got a lovely Fabia 2 1.6 tdi se  (2010) that's had to have new front discs (within guarantee); had to have the aircon re-gassed 2 days out of warranty; Been told at its 1st MOT that both the front and rear wheel tracking is way out and will cost £90 +VAT to retrack; The heater resistor pack failed this July (2013) when the temperature went upto 34C (UK) and have been told by the Reading Skoda dealer that it will cost £600 to £700 approx + VAT to remove the dashboard complete to get behind the moulded in glovebox to replace the fan resistor pack (£48 + VAT) ........  My previous car was a Ford Mondeo hatch 1800 petrol .... It cost peanuts to service and over 16 years the only things that needed replacing were windscreen wipers and tyres!

 

So I'm going to take a saw blade and saw out the glovebox to get to the incoming airduct and replace the resistor pack with a £3 pwm (pwm = pulse width modulation) circuit board.  The circuit that I'm going to install is both simple homemade and will plug into the resistor pack plug in the airduct behind the glovebox.  It won't fail because it doesn't get warm.  .... Don't know yet how I'm going to remount the glovebox .....   :) :) :) 

 

Let's explain:   The resistor pack is set in the fan heater incoming airduct because on settings 1, 2 and 3 resistors are switched in so that the amount of current drawn by the fan is constant: ie the wattage used by the fan is the same for settings 1, 2, 3 and 4.  So on settings 1, 2 and 3 the resistors get hot and are cooled by the passing airflow: Setting 1 gets hottest as it has to waste the most energy ..... 2 is less hot; 3 gets less hot than 2 and setting 4 bypasses the resistor pack and so when the resistor pack fails only setting 4 works.    The resistor pack comprises 3 wirewound  resistors and a thermal cutout resistor which fails at 270C.   It's set in the airduct to cool it ... and waste energy .....

 

This technology of using massive low ohm wirewound resistors giving off oodles of waste heat is out of the ark. It's 19C technology .... and at £48 + VAT for a resistor pack for an item which according to VAG is one of their best sellers (ie a boon to all VAG servicing agents)    A simple solution is to replace the resistor pack with an unregulated voltage circuit in the range from 10v to 15v that uses pulse width modulation ("pwm") to control the fan speed.  PWM is such that if if the pulse is for each cycle at whatever generated frequency (I'm going to use 20k Hz) on for say 25% of the time and off for 75% of the time, then the fan will operate at  25/(25 + 75) = 1/4 rated max speed.  50% = 1/2 rated speed;  75% = 3/4 rated speed (about because fan blade friction etc has to be taken into account)

 

The circuit comprises a few small capacitors, a few 1/4W resistors, a switching chip (£0.17) and an output MOSFET transistor with a small heasink.  It's 1960's technology and it's cheaper to make that the out-of-date super-profit-making VAG resistor pack!

 

BUT, my problem is how to get to the failed resistor pack.  I'm NOT paying £600 to £700 + VAT to have the complete dashboard removed (plus the special tools that are required to effect removal!!!!!)    So, I'm going to take a thin oscillating hacksaw blade and cut through the glovebox lower spindles and see what happens ... I might have to cut through the upper stops .... But what have I got to lose?  Nothing:  It's only plastic.

 

I think that 1) where any part is prone to failure, then it should be easily accessible; 2) that where any part is prone to failure that there should be an easily accessible workshop manual to tell you how to do it.  (I had to use the UK Freedom of Information Act to get the Reading Skoda dealer to find out that the WHOLE dashboard had to be removed to get to this commonly failing but essential for cabin comfort part)

 

I bought Skoda because of their oft quoted reliability.   Perhaps I've just got a rogue car ...... Sadly, it's the worst car for reliability that I've had since a 2nd hand mini in 1963... OUCH!

 

If anybody has any other ideas .... or can offer a better solution on how to rip out the glovebox ..... :( 

 

 

 

Nige  (Reading)

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Quote " (2010) that's had to have new front discs (within guarantee); had to have the aircon re-gassed 2 days out of warranty; Been told at its 1st MOT that both the front and rear wheel tracking is way out and will cost £90 +VAT to retrack; The heater resistor pack failed this July (2013)"

 

If it were mine nigech I would be on the phone to Skoda Customer Services. Mention all the items from new.

 

I trust you did not have to pay for the re gas. (although this is a service item) but I would have thought Dealer could have done it as a freebee.(goodwill)

And WHO told you F & R wheel tracking is out? Apart from tyre wear how did they know.

 

More info needed as this does not sound right.

CD

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I think you show some basic errors in your knowledge of electrics / electronics

 

the power transistor you choose to use will heat up in the same way, due to the same ohms laws P=I2 x r where r is the internal resistance of the transistor (be it normal NPN or FET) the inlet / cold side where the fan resistor is is an unfriendly environment to electronics due to temp and humidity variations as the only thing between that and the outside world is a pollen filter, due to this you will need a heatsink, and no electrolytic capacitor,

 

also if you are going to be chopping 5-6 amps at 20khz you better have some excellent smoothing capacitors or you are going to have a whole load of trouble with the electronics in the ECU and other modules which will not be covered under warranty when they see modifications to the electronics in the car

 

this is why they use a simple dropper resistor which reduces current and voltage to the fan motor to control the speed

 

one thing the main cause of the resistors going is clogged pollen filters reducing airflow and cooling, causing it to overheat and fail

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Fully-on resistance of a half decent FET is really, really low; so there won't be nearly as much power wasted as heat compared with the resistor solution. I must admit though that the OP's description of constant current in the fan motor irrespective of setting seems unlikely.

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I agree it will be low but probably still need a heatsink when running on speed 3, also lots of noise from chopping the power at 20khz, also not taking into account the inductance of the fan motor unless he is going to smooth the 20khz before applying it to the motor

 

I would be inclined to just swap the resistor and pollen filter than trying to design and build a custom controller, as I think the resistor only controls 1-3 and speed 4 goes from switch direct to blower motor which is why it always works when the resistor fails

 

to do that it is undo battery negative leave 10-15 minutes for the airbag controller to lose power then remove glove box and passenger airbag to get to resistor if memory is correct, plenty of online videos, no special tools other than a set of torx bits and small hands

 

also as skoda and dealers are private companies, FoI's do not apply to them

 

I do get the feeling he is being given the run around for a simple job, £48+vat is steep for the fan resistor, last time I got one it was just over £30 I think

 

quick google found this http://www.justanswer.com/uk-car/7rj2g-fabia-mk-2-skoda-fabia-mk-left-hand-drive-climate-control.html

 

and plenty of "new" resistors on ebay for mk2 fabia for less than £20

Edited by bluecar1
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Hi Wino,

 

That thread applies to Fabia I .... The Fabia II is (apparently, according to the local Skoda dealer) and complete moulded and prefabricated unit ..... and there's no accessible  online workshop manual available!  (Or at least I can't find one)

 

Cheers,

 

Nige

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Hi Bluecar1,

 

You right that my knowledge of electrics and electronics is less than basic, but I did say that the MOSFET would have a heatsink (which I seem to have spelled 'heasink' in the original post) and the whole new circuit board would made to on the original twist off 'plug' to replace the resistor pack so being in the airflow .... and the only electrolytic capacitor would be the initial smoothing capacitor  say 2200 micro-farads (not calculated yet) across the say 13.4v alternator supply. 

 

The pollen filter was replaced  two weeks before the resistor pack failed. 

 

The quick google  which turned up:

 

"Expert:  Mike replied 4 months ago.

Hello again - Thank you for your reply -

Thats fine, no problem at all - 

I will give you the instructions you need then to progress with this / complete the job for you as follows :
 

Remove the glove box:

1. Remove the panel, to the left of the glove box - This is the "end panel" on the dash -- the part that you can only see when the door is opened - it just pulls off.

2. Remove the three screws along the top of the glove box and two screws at the bottom of the glove box - these are Torx head screws - then pull the whole assembly forward and down to remove. It can be awkward / stiff -but it will come.

Drop the lower cover panel down - it just un clips..

3. Disconnect the light unit etc and the whole assembly can now be laid down in the foot well.

etc ....."

 

.... appears to apply to the Fabia I glovebox/dashboard

 

I hadn't thought about possible interference with the ECU using a simple PWM .... UMMMM.... Perhaps you are right to say just replace the resistor pack as a an entity: It's the simplest solution that could fail again someday ..... but I've still got to get the glovebox off .....

Cheers,

 

Nige

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Hi there, Wino,

 

I didn't see that post .... Sorry!   Here it is as it could be a solution which I'll try tomorrow (Wed 25 Sept) :   "Hi mate, open the top glove box and remove the 2 torx screws. A pull outwards and the glovebox will come out of the dash. If you then look into the hole you will see 3 torx 30 screws. These hold the airbag frame in the dash. Remove the screws carefully (dont drop them behind the dash!). The cover will then come up out of the top of the dash but it will be quite tough to remove. Probably a good idea to disconnect the battery and then disconnect the airbag, make sure you dont have a static build up in your body, touch the door striker to make sure. Once the airbag is out of the way you can find the resistor down in the hole on top of the airbox. Its a bayonet fitting so twist it and it should come out, its a bit fiddly. Disconnect wiring fit new resistor and rebuild in reverse order. Reconnect battery and test. "

 

If this is correct, why did the local Reading Skoda dealer tell me that the whole dashboard would have to be removed etc ????????

 

Let's see what happens tomorrow and see if I can find the 3 torx screws having removed the top glovebox .... I'll take photos of each step and post what I find ..... :)

 

Cheers,

 

Nige

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Hi Leepatrick01,

 

Rear wheel tracking problem:  It was an advisory on the MOT.  The local Reading Skoda dealer said that it would need specialist tracking to correct this; £90 + VAT   (I can post the MOT advisory if required)

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Hi Tech1e,

 

BRILLIANT!  Problem solved. Switched off the airbag.  It took 16 minutes to follow your instructions and get the resistor pack out, take photographs and then put everything back. It was a bit fiddly, but overall a doddle.   I'm not going to make a PWM to replace the resistor pack .... just get a new one off ebay

 

Cheers and many thanks

 

Nige

 

(If anybody wants to see the photos then I'll upload them later today)

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so silly question do you trust any information provided by that dealer in relation to the tracking or anything else now ?

 

if there is a job to be done a skoda there is someone on here who has done it and can tell you exactly how, what part and where to get them and any problems you may encounter

 

between us we have probably seen every fault code, and heard every noise

 

enjoy the forum and car

Edited by bluecar1
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Do I trust the local dealer?   ..... Ummmm.   I ordered 2 resistor packs @ £11.50 inc p&p yesterday afternoon off Ebay and they arrived 1st class post this morning.  I timed myself putting the new pack in:  It took 12 minutes to take out the top glovebox, passenger airbag; remove broken resistor pack; put new one in; reassemble; test (Yes, the fan is working again on all 4 settings) .... noted that the centre dash airbag warning light said passenger airbag switched off, so switched it on again. :hi:

 

This BB has just saved me over £448 to £648 + VAT @ 20% .... So do I trust the dealer over re-tracking the rear wheels?  When I asked the dealer re re-gassing the A/C he said it was quite normal for A/C systems to need regassing every couple of years. .... (I kept my mouth shut and silently said "*******s" :  The A/C had been run regularly so that the R-whatever gas would keep the seal lubricated .... I said that my Mondeo hadn't needed re-gassing in 8 years and the same applied to my wife's Rover 25.... )

 

I'm really cheesed off that the tech-chief at the dealer said the whole of the dashboard needed to be removed .... They gave me a printout from their workshop manual of the airduct and resistor pack unit, but nothing on how to replace it or any reasonable explanation as to why the resistor pack had failed so early in its life!  ..... Is it really worth moaning to Skoda UK about a dealer whose technical abilities are now, in my opinion, suspect?

 

There's a very nice family run general garage about a mile away which looks after my wife's car and my daughter's car ..... I thought that having bought a Skoda from a dealer in very smart, clean premises that they would know best ..... But ......

 

Anyway, apart from that, my Fabia 90ps tdi is a really great little car.

 

Thank you all here for solving the dreaded resistor pack proble and for all the other advice,

 

Nige

Edited by nigech
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