Fuse help please

[a666andy]

Evening all

 

Can anyone advise me correctly on this fuse number 4 I believe please. To make it very obvious I've circled the fuse and also added the fuse diagram from the back of the cover which is confusing as to me, even after seeing a previous post about it being the wrong way round or something....

 

Anyway, my Aircon is currently not working, even after a regas attempt and it supposedly holding the vacuum / pressure test so I thought I'd double check fuse 16 as that is what is supposed to be for the aircon according to the handbook.....I think?

 

Anyway, this fuse circled, when pulled out seems to be number 4 (it has a 4 on the plastic it slots into so I'm sure this part is right) and does look like it is blown

 

The diagram on the back of the cover shows a nice little pic of what seems to be the same part as for fuse 16 which is the aircon I believe (Fuse 16 looks ok)

 

 

However, the myskoda handbook app tells me that Fuse 4 is "WIV, parking light, dimming mirrors, pressure sensor, telephone preinstallation" I've never used the parking lights and don't think I have dimming mirrors (or maybe they are just not working?) no idea what the pressure sensor is and my bluetooth phone works ok but presume this is not the same as telephone prep.

 

I'll obviously replace the fuse anyway, but can anyone confirm for sure what this fuse 4 is actually for?

 

Thanks in advance

[peter_k]

Just a suggestion for the "pressure sensor" and air con symbol on fuse 4. I think some cars have a pressure sensor on the low pressure side of the air con system to prevent the compressor running with low refrigerant.

[chimaera]

The card inside the cover is a mirror image of what's installed. The RHD fuse panel is a mirror image of the LHD one (which is placed on the left hand side of the car) and it seems they've only ever issued cards for LHD. What all that means is that your identification of that fuse number is correct.

 

As for what it does, from the wiring diagrams, fuse 4 seems to be connected to two things: air quality sensor and high pressure sender. The air quality sender is part of the control loop for the air conditioner, and I'd guess the high pressure sender is something to do with it too. At any rate, it's a blown fuse, so replacing it would be a good idea no matter what. If it blows a second time though, it would be a good idea to do some more detailed fault finding to determine why it has blown.

 

It does happen that fuses are reassigned during the production run, so the manual may be quoting all the possible systems that the fuse controls, rather than what it's actually doing on your car. If you post the year (and month) of your car I can check the specific diagrams for it and see what's what.

[a666andy]

Many thanks both

 

The fuse has been swapped but after going for a regas on the aircon yesterday, they've left it empty because it wasnt working.... so i dont know if the new fuse has made any difference to my aircon issue.

 

Thanks for offering to check, it was first registered end of sept 2011, 2.0 tdi elegance estate, variant accfgbx01

[FlyingSpanner]

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Edited 9 January, 2019 by FlyingSpanner

[a666andy]

I'm sure I don't have a anti dazzle mirror, it's just basic, my reverse lights have been working all along but no idea about the pressure sender but it at least is related to the aircon. Although my oil level sensor is throwing an error at the moment too (waiting for mech to check the wiring as already had a new sensor put in last week)

 

Anyone else can tell what this fuse is for?

 

Thanks

[chimaera]

The newest wiring diagrams I have access to on my work computer are for cars built from November 2010 on, and show fuse 4 doing the same job as I listed above plus the automatic anti-dazzle mirror (the original build from March 2008 didn't have the mirror function). As I said previously, the owners manual must list all possible vehicle functions that the fuse could be used for, which could well be more than is installed on your specific vehicle.

 

Of interest for your issue is that the oil level sensor and oil temperature sensor are also assigned to fuse 4 in the assignment list at the end of the wiring diagrams.

 

Looking at the specific wiring diagrams for the aircon system, fuse 40 in the dash fuse panel is supply power to the fresh air blower switch on cars with manual aircon (not Climatronic climate control). Fuse 9 supplies power to the blower relay.

 

If you have Climatronic, fuse 22 is indicated for the blower control unit.

 

My guess here based on what you're describing is that there's a few frayed wires going to the oil sensors and the high pressure sender, and that they're shorting out intermittently and blowing that fuse. I'd find out where those two components are and trace them back to a point where they meet and work from there. It's going to be a slow and frustrating job.

[a666andy]

Many thanks for that, it's all started to link together now and make sense

 

Will start with the wires from the oil level sensor and work back, hopefully it's not a long search

 

Cheers

[steveja2]

Hello ! Sorry to drag this back up after a couple of months... But did you resolve your issue with Fuse no 4 ? I have a 2011 Superb and it is blowing fuse no4 EVEN WHEN THE IGNITION IS OFF AND KEYS ARE OUT.

I believe that fuse supplies the HIGH PRESSURE air con sensor in the front of engine bay near drivers side headlamp, its also the Oil Level / Temp sensor on the sump, its also for the reversing sensors (and probably reversing lights ?). 

I am REALLY struggling to find where mine is shorting out to ground... Running a fault check with VCDS reports those things mentioned above as not working (but then it would say that because as soon as the fuse blew all those things lose power !)

I have unplugged my Air con gas sensor, the oil level / temp sensor and pretty much EVERY connector I can get my hands on behind the dash (I've removed the central vents / glovebox / side vents / radio etc) BUT I STILL HAVE ONLY 5 ohms to ground on that damn fuse !

I am thinking its a wire chaffing somewhere against the frame but I simply cant track it down !

 

AND BTW are there any good wiring schematics for the SKoda Superb MkII ?? I am struggling to find anything... Keep getting results for Octavia but am unsure if I can trust the schematic to be accurate (an incorrect wiring diagram can be worse than no wiring diagram !)

 

Thanks for any advice !

 

Regards

 

Steve

[chimaera]

You can buy the wiring diagrams (and all other repair manuals) through Skoda's erwin portal. A day's access is about €30 and is plenty of time to explore the site and find what you need.

[Breezy_Pete]

1 hour ago, steveja2 said:

Hello ! Sorry to drag this back up after a couple of months... But did you resolve your issue with Fuse no 4 ? I have a 2011 Superb and it is blowing fuse no4 EVEN WHEN THE IGNITION IS OFF AND KEYS ARE OUT.

I believe that fuse supplies the HIGH PRESSURE air con sensor in the front of engine bay near drivers side headlamp, its also the Oil Level / Temp sensor on the sump, its also for the reversing sensors (and probably reversing lights ?). 

I am REALLY struggling to find where mine is shorting out to ground... Running a fault check with VCDS reports those things mentioned above as not working (but then it would say that because as soon as the fuse blew all those things lose power !)

I have unplugged my Air con gas sensor, the oil level / temp sensor and pretty much EVERY connector I can get my hands on behind the dash (I've removed the central vents / glovebox / side vents / radio etc) BUT I STILL HAVE ONLY 5 ohms to ground on that damn fuse !

I am thinking its a wire chaffing somewhere against the frame but I simply cant track it down !

 

AND BTW are there any good wiring schematics for the SKoda Superb MkII ?? I am struggling to find anything... Keep getting results for Octavia but am unsure if I can trust the schematic to be accurate (an incorrect wiring diagram can be worse than no wiring diagram !)

 

Thanks for any advice !

 

Regards

 

Steve

What's your engine code?

 

And is it the Climatronic A/C system? In which case Air Quality sensor/wiring may be another suspect.

Edit, sorry, I see you already mentioned that one.

And it shouldn't be live with ignition off, reading more of what you wrote. Do you measure 12V at either end of the fuseholder with fuse unfitted, ignition off?

Edited 6 August, 2018 by Wino

[steveja2]

Hello and thank you for the repsonses.

 

I think I shall indeed subscribe to Erwin - I looked at it but wasn't sure if I would be able to get the correct diagrams etc I need - but certainly useful and worth a shot.

 

My engine code is CFFB

 

Its a 2011 Skoda Superb Estate 2.0 Diesel.  It has the automatic Climatronic control but does NOT have an auto dimming rear view mirror (which is something else apparently connected to Fuse no 4).

 

Thanks,

Steve

 

[Breezy_Pete]

I'm not coming up with anything you haven't mentioned, device-wise, but I'd be interested to know which side of the fuseholder is showing 12V with keys out of ignition, that might help you track down the fault.  Must be the side that's supposed to be 12V only with ignition on, I guess?

 

 

[a666andy]

Steve

 

I'm not sure on how accurate this is (maybe someone else may be able to confirm) but my mechanic said there was supposedly a bulletin that said Fuse 4 is too low an amperage and to upgrade it to 7.5A..... Mine has been swapped and hasn't blown again since and I can only trust his word for it as my Aircon is working again as normal and my oil level sensor warning is also gone.

[steveja2]

ONce again thanks for all the feedback...

 

Wino - the 12v supply is coming in at the top of the fuse (as expected) even with ignition OFF... There is a resistance of 480 ohm to ground on the top of the fuse carrier, the bottom of the fuse carrier shows only 5 ohms to ground with ignition off but surprisingly the resistance INCREASES to approx. 10 ohms when ignition turned ON !?!

 

A666andy - I haven't tried upping the fuse rating - so I will have a go at that, HOWEVER, with only 5 ohms resistance down to ground on the fuse I suspect that it will simply blow a 7.5 amp fuse too - but certainly worth a try ! (I did consider shorting it out and see where the smoke comes from !! - but it would probably explode the battery and melt half my loom ! 

 

Having disconnected the High pressure sensor, the oil level sensor, the parking sensors and pretty much every connection I can reach under the dash I think I need to look at the reverse light switch but I am not sure if its located on the gearbox or the gearstick mechanism...?  There is certainly some relationship with the reversing sensors and / or lights...

 

Thank you.

 

Steve

[steveja2]

THanks again for the advice - and apologies... I think I was talking nonsense in my original post - having just checked for voltage on either side of the fuse carrier with the fuse out, I find that there is NO voltage (with respect to ground) on either end until I turn on the ignition - So my original comment saying it blows the fuse even with the ignition OFF was nonsense ! I was thinking that it blew a fuse as soon as I plugged one in - but it couldn't have done as there is no power to that fuse when ignition OFF.

I've noted that the top of the fuse (incoming) is 480 ohm to ground when ignition OFF but changes to infinite (open circuit) with ignition ON. The bottom of the fuse (outgoing load) is showing 5 ohms to ground with ignition OFF and it jumps up to 10 ohms with ignition ON.

 

By the way - where would I find the air quality sensor ?? - I'm not sure if I've managed to track that one down yet and disconnect it (and I've seen it mentioned in other posts).

 

Thanks,

 

Steve

 

[Breezy_Pete]

Not sure about the air quality sensor, but reverse light switches tend to be on the gearbox for manual cars, and on the selector mechanism for autos. If yours is manual, I'd guess that the wiring for that is more vulnerable to damage than the air quality sensor, but maybe it's just a fuse rating issue, as Andy suggests? Try a 7.5A and see if it still blows?

[steveja2]

YUp - I will take a look at wiring going to the gearbox... Mine is indeed a MANUAL box - strange thing is that it still displays what gear I am currently in on the Maxidot display - so I'm guessing that part of sensing the gear selected is working OK - but am not sure if there is a separate switch on the gearbox for the REVERSE SELECTED position - I will have to try and find it... In my selection of fuses the only next size up is 10 amp - but I guess it wont hurt to try it because if its hard down to earth then it will simply pop that one too...

 

Originally I focused all my attention on the HIGH PRESSURE switch of the air con - because the scenario when it first failed was that I was simply parked with engine running with air con ON for about 10 mins - then it just started to get warmer. So I switched off and restarted the car - when I restarted it it showed "OIL SENSOR - WORKSHOP" on the display with image of oil can - so I assumed (bearing in mind I wasn't actually travelling and it was fine for 10 mins) that I must have blown the high pressure switch on the air con - but I have since disconnected the switch AND the compressor BUT still got fault with it being down to ground... So may just be coincidental...

 

I'll try a bigger fuse, and try and find reversing switch on gearbox... but its starting to look like ripping out loom and tracing cables !  :(

 

And if I find it I will post here to try and help others because I've come across other threads describing same fault where the solution was never posted - and there was no response to several others asking "hey I have the same problem - what did you find..."

 

[Breezy_Pete]

Gear selected indication may well be a calculation with rpm and ABS wheel speed sensors as inputs.

[chimaera]

47 minutes ago, Wino said:

Gear selected indication may well be a calculation with rpm and ABS wheel speed sensors as inputs.

Yeah, MFD gear indicator on manuals is just some calculation based on road and engine speed. DSG uses actuator position sensors.

[steveja2]

Well this is interesting... Due to an earlier post suggesting that a comment was made to UP the fuse rating from 5 amp to 7.5 amp I decided to give that a go - but I didn't have any 7.5a only 10a ! But thinking its probably a short down to the chassis somewhere I thought all it would do is blow the fuse.... So I inserted a 10Amp fuse and turned on ignition - I heard a *CRACKLE POP!* come from the engine bay !   :(  Followed by a slight whiff of that dreaded "burnt out" smell...

Surprisingly the fuse didn't blow !!

SO I powered down and restarted the car... The oil temp/level sensor alarm DIDNT come on and its now showing oil temp on the dash, the reversing lights and reverse sensors are working OK !

 

I haven't had chance to try the aircon because I have to put all the connectors to fan etc back in... And at least now I believe I should be looking in the engine bay for the fault.

I will get VCDS plugged in and see what is now showing as faulty...

 

Will investigate further and post results... Hopefully it might help someone else avoid having to fork out £100's to an auto electrician spending hours fault finding... 

[Breezy_Pete]

Very interesting. Maybe one or a few strands of wire were shorting, but the increased current burnt them out.

[steveja2]

Yes I did wonder if bumping up the current like that cleared the fault....

Update:

So I've plugged pretty much all the connectors back in,

The air con and blower etc are working OK ! YAY ! (can take the family on holiday now without 2 hot kids whinging all the way about the heat !)

 

The only thing I seem to have outstanding is an "AIRBAG ERROR" warning and the airbag symbol on the dash... am hoping that it might just be a connector I've missed or maybe it needs resetting with VCDS since I removed the glovebox and disconnected the airbag keyswitch.

 

Given time I will fire up VCDS and clear the errors and check for any outstanding issues.... I might also try a 5 amp fuse back in to see if it pops (I haven't done it yet but I will measure the resistance on the outgoing load side of the fuse to see if its still 5 ohms or if has indeed blown the fault away )

At least now if VCDS flags something up specific like ABS SENSOR on Nearside Front OPEN CIRCUIT then at least I will know where to look !

 

PS = Thanks guys for the assistance and advice !   I will share any further findings in the hope that it may help others.

 

Steve

[steveja2]

OK final update on the issue of the blowing fuse...

 

After bumping up the rating of fuse F4 from 5 amp to 10 amp I heard the sizzle *POP* of something burning out in the engine bay. But afterwards everything appeared to work fine !!

But I was convinced that something had burnt out (am familiar to the smell of burnt out motors etc) I ran vcds, cleared all faults and only 1 returned... "Air quality sensor OPEN or SHORT circuit".

Went on a mission to find location of the air quality sensor - am pleased to say I did indeed find it and it was definitely burnt out !

 

So for the benefit of anyone coming across this post due to similar symptoms, here is what the trouble was for me...

I suspect that a previous post from someone saying he fitted a bigger fuse and the problem went away was probably similar issue - but under normal driving conditions you would never even notice if the air quality sensor was working or not (they're a bit rubbish at what they do anyway !)

 

My short was caused by the air quality sensor - Part number 1k007659

It is located under the black plastic cover which is at the bottom of the windshield (the guard which covers the window wiper motors).

It is on the PASSENGER side of the vehicle - thankfully that half of the cover simply pulls off without having to remove wiper blades.

Under there is another black cover held on with 2 torx screws (this covers up the main air intake into the cabin)

The sensor is clipped to the side of the air intake box with a steel folded clip which has barbs on it to grip the plastic.

The sensor is connected via a 3 wire plug.

Hopefully there should be some pics below showing the location of sensor and how it was burnt across its pins....

 

Location of sensor - right hand side of engine bay right up near windscreen... in bottom left corner of that grille...

 

 

Sensor is near bottom left hand corner of the grille clipped to plastic.

.

 

The connector to my sensor showing evidence of burning...

 

The sensor itself showing the melted plastic around the connection pins (one pin was very wobbly - almost falling out) It also smelled like burnt out motor.

 

I am pleased to have found this and hope it helps other people.

 

Looking back at the posts I realise that this is all thanks to Wino and a666andy who suggested upping the fuse rating. (Which led to the distinct "snap, crackle, *POP* followed by a burning smell !)

NOTE TO Andy..... It might be worth checking your air quality sensor, if you situation is like mine, then upping the amperage of the fuse might have simply burnt out the sensor completely thus allowing the other devices to function correctly... Not that it really matters if the air quality sensor is not working !

 

Many thanks to everyone ! Forums and Professor Google have saved me 100's of pounds by avoiding paying out for hours of electrical fault finding (and I've learned more about my car in the process)

 

Do Haynes not make a manual for the Skoda Superb !>!??

 

 

Edited 7 August, 2018 by steveja2

[a666andy]

Glad all is looking good for and I'll be checking my air sensor too! Thanks