Intermittent fan fault

[Mikek3111]

Well. Light on again this morning, fans going full whack. Replaced the sensor in that bottom hose and made absolutely no difference. Now can't find my multimeter so just ordered a new one to be here tomorrow.

I haven't done anything about downloading the current-flow diagrams, and it sounds like I would have struggled anyway, due to not knowing about the existence of that sensor, and not thinking about thermoswitch as something that hasn't been changed 'til I noticed it wasn't in your list of things done.

Which way do the wires head from the back of that lower sensor, towards the fans or towards the e-box/elsewhere?

Still might do it though for future reference.

The wires from that sensor only have a small segment about 5-6" and go to the right (away from the fans) and into the main harness.

No amount of "wiggling fuses" helped today so will strip the fuse box out again this afternoon and inspect it again and will run continuity checks and voltage checks on wiring tomorrow when multimeter arrives.

Only positive is I know it's not a sensor issue as these have all been replaced now unless there's something I'm missing that I'm not seeing?

Edited 6 July, 2016 by Mikek3111

[Breezy_Pete]

Sorry to hear it's still playing up.

 

Any photos you can take while investigating the e-box may well be helpful to others in future.  Is there actually a circuit board inside there, do you know?

[Mikek3111]

Sorry to hear it's still playing up.

 

Any photos you can take while investigating the e-box may well be helpful to others in future.  Is there actually a circuit board inside there, do you know?

I need car to pick daughter up from nursery at 11:50am. Once I'm back I'll pull out the fuse board and take some pic's as I strip it down.

[Mikek3111]

Ok, so removed fuse box cleaned, refitted, then the plugs that the ebox clamps into I've run a hairdryer over to ensure no moisture there. Refitted and fault still remains.

Will have to wait until tomorrow now for my new multimeter to arrive and will have to rein spect the wiring.

[Mikek3111]

Ok so got a few hrs to spend on the car this afternoon. Checked wiring to fans, continuity on earth and 12.4v on power side so all ok there. Then noticed that my ambient temperature sensor wasn't fitted into the bumper and just dangling. Disconnected the sensor and fans immediately stopped?

Phoned skoda and spoke to their master tech and ambient temp sensor not in any way connected to the fans, so why has the fault suddenly cleared? Ordered a new sensor £18.44 not in stock so have to wait a few days but this car puzzles me more and more?

Would have thought Ecu or PCM would take readings from the engine temp sensors not outside temp sensor?

Anyone else had a similar issue? Or could this just be a random coincidence that the fault has intermittently cleared after removing the sensor?

[tonyuk74]

Just a thought. Could it be something with the aircon / climate control circuit? Fans come on with aircon running. Have you checked air con turns off ?

[Mikek3111]

Yeah aircon turns off as in blowers inside cease however, as both engine fans run high speed I've no other way to confirm that.

It did cross my mind as the aircon fan has no direct power and borrows/loops from the cooling fan. However, the ambient temp sensor doesn't appear to be connected in anyway to the coolant circuit, or the climatronic circuit which is what has me and the skoda master tech confused

Edited 11 July, 2016 by Mikek3111

[tonyuk74]

Don't quote me on this but I would have thought outside temp would be linked to aircon. I can't imagine fans running in winter with aircon on been used for de-misting or engine would never heat up.

[Mikek3111]

Don't quote me on this but I would have thought outside temp would be linked to aircon. I can't imagine fans running in winter with aircon on been used for de-misting or engine would never heat up.

That was my thinking, however, the wiring diagram (I didn't see this one as it was master tech looking for me whilst on the phone) stated that the ambient sensor has 2 wires which both run behind the dash and don't appear on either the cooling or climatronic wiring diagrams. I questioned as to if it shared an earth somewhere with either system but apparently not which is rather confusing as to why unplugging it cleared the fault (potentially)

[tonyuk74]

Id be tempted to leave it unpluged a few days and see how it goes

[Breezy_Pete]

That was my thinking, however, the wiring diagram (I didn't see this one as it was master tech looking for me whilst on the phone) stated that the ambient sensor has 2 wires which both run behind the dash and don't appear on either the cooling or climatronic wiring diagrams. I questioned as to if it shared an earth somewhere with either system but apparently not which is rather confusing as to why unplugging it cleared the fault (potentially)

Do you get a (correct) readout of ambient temperature somewhere on the dash?

 

Everything communicates with everything else these days via the CANbus. So the information (or duff information if it's damaged) will be communicated from the dash/instrument module to all the other modules that might be interested.

 

Edit: Seems strange that the fault code you've seen via VCDS is not  e.g. "ambient temperature sensor implausible value" or words to that effect though? (Which might be expected if it was shorted, as another post from you today suggests.)

 

Connect VCDS to Instruments, module 17 I think, and see what the ambient temperature reads in measuring blocks with and without the sensor plugged in?

Edited 11 July, 2016 by Wino

[Mikek3111]

I get the temperature on dash and instruments which appear correct. With it disconnected though you get no reading wether on dash or vcds

[Breezy_Pete]

Hmm, that suggest the sensor is OK, are you sure you didn't touch your meter probes together accidentally when measuring the sensor earlier?

[Mikek3111]

No. I tried several different times with the same results. i have ordered a new one. Will leave it disconnected and ensure the back of the plug is sealed when I fit the new one as I've seen people have had them fail due to water ingress.

I just don't understand if that was faulty why it would bring the fans on and give a P0480 code? Makes no sense according to skoda a own wiring diagrams.

[Breezy_Pete]

As I speculated above, the various 'interested parties' among other modules will be aware (via CAN) of the ambient temperature readings that the instruments module is measuring.

In the absence of other high temperature readings from coolant sensors, I'd be surprised that ambient temperature looking super-high (as a shorted sensor might appear to indicate) would bring on fans though.

 

If you look at measuring blocks for HVAC, what refrigerant pressures do you see coming from G65?

[Mikek3111]

Have to check tomorrow.

[Mikek3111]

Replaced the ambient temp sensor today. Absolutely no change at all. Light still on and fans still going full blast.

[Mikek3111]

Fingers crossed I think it's fixed. Put VCDS on after replacing the ambient sensor and it was showing a different code. P1660 irc. Remembered I'd pulled 50A fuse, so reinserted fuse and cleared fault. Light went off. Gave it spin round the block/village, and hasn't reappeared so keeping everything crossed that it stays that way.

No I can focus on last fault code/no refrigerant and the MOT advisories, rear pad and 2x tyres.

Came very close to pxing it :( which I really don't want to do.

Will monitor it and see how it goes?

At a last resort, I know these cars are fairly over cooled anyway, I don't really live in an area where I get stuck in traffic, would I get away with just leaving them unplugged? I know possibly of overheating but we don't exactly have tropical climates. Ideally I'd like the car to work as Intended but just a last resort thing?

[Breezy_Pete]

Did you have a look at the G65 refrigerant pressure reading? If that's sometimes giving duff information to the HVAC module it might be involved in fan strangeness.

A/C definitely won't work if you disconnect the fans, other than that you might be OK until that hot day when you're stuck in traffic for too long. I wouldn't have confidence in a car with no fans.

[Mikek3111]

Did you have a look at the G65 refrigerant pressure reading? If that's sometimes giving duff information to the HVAC module it might be involved in fan strangeness.

I tried. Didn't see it listed. However, I know I have a small hole in my condenser which is due to be replaced and regassed so pressure reading will be low anyway. It's recently had the high pressure sensor replaced.

[Mikek3111]

Faults back again :(

[Breezy_Pete]

Sorry to hear this Mike.

Don't suppose you still have the old fans that got replaced a while back?  I'm curious about the rumours of integrated control units. 

[Mikek3111]

Sorry to hear this Mike.

Don't suppose you still have the old fans that got replaced a while back?  I'm curious about the rumours of integrated control units.

No I took them to the recycling centre last week.

The light came on half way down to London. Dropped kids off when we arrived and fault cleared, when I started car to leave, fault reappeared but cleared then came on halfway home. When I got home it cleared again? Doesn't seem to be any pattern as to when it happens as I've had it from cold. SWMBO is getting sick of it and wanting to take a loan out to change the car, but we really can't afford that so I am trying hard to stop her doing that and keep this on the road.

[Tech1e]

Sorry to hear this Mike.

Don't suppose you still have the old fans that got replaced a while back?  I'm curious about the rumours of integrated control units.

They do indeed, big fan is a master control unit whilst the smaller is a slave unit connected by LIN bus.

[Tech1e]

That was my thinking, however, the wiring diagram (I didn't see this one as it was master tech looking for me whilst on the phone) stated that the ambient sensor has 2 wires which both run behind the dash and don't appear on either the cooling or climatronic wiring diagrams. I questioned as to if it shared an earth somewhere with either system but apparently not which is rather confusing as to why unplugging it cleared the fault (potentially)

The AC system has another temp sensor mounted on the intake of the heater box under the scuttle trim that shuts off the AC in the event of low temps.