Haldex failure scare

[Vrstdi estate]

During a normal drive recently, I pulled out of a junction to find that my 2.0- Tdi Yeti 4x4 was scrabbling for front grip, normally it would shift drive to the rear without creating any fuss or drama which concerned me.The road where I live is a loose unadopted lane with a steep approach so I tried a hill start and again the FWD struggled for grip.

 

I saw that there was a chap locally whio had the diagnostics cable and he very kindly showed me that there was a fault with the Haldex amongst one or two other alerts however no warning lights were showing. I checked all fuses and tested again and still no rear drive was apparent.

 

I checked in with Simpsons in Colne and they put the car on the rollers however the rear drive was working so they hooked it up and sure enough there were a catalogue of faults; what transpired was that the battery had become quite drained through lack of longer journeys of late and what the car had done was to halt all non-essential processes to ensure that the engine management and brakes were given priority. They reset the system and all is fine - No charge! 

 

When I was contemplating a monstrous bill for a failed 4x4 system, I am a very happy man and very grateful for the superb service at Simpsons.

 

 

[TeflonTom]

Battery drained? What's the punch line? It takes less than 10 mins roughly to fully charge a discharged battery through just normal driving

[muddyboots]

Battery drained? What's the punch line?

 

 

No charge! 

 

It's right there I think

[muddyboots]

On a more serious note. How old is the car ? Mileage ?

[Llanigraham]

Battery drained? What's the punch line? It takes less than 10 mins roughly to fully charge a discharged battery through just normal driving

 

Sorry Tom, but it takes a lot longer than that!

[TeflonTom]

Sorry Tom, but it takes a lot longer than that!

We're not talking a £20 Argos trickle charger, the alternator on most vehicles will give out at least 80 amps on full field duty, between 5 and 8 miles it will be fully charged, I've even proven this before with a deep cycle drop tester.

[Totally Square]

...I checked in with Simpsons in Colne and they put the car on the rollers however the rear drive was working so they hooked it up and sure enough there were a catalogue of faults; what transpired was that the battery had become quite drained through lack of longer journeys of late and what the car had done was to halt all non-essential processes to ensure that the engine management and brakes were given priority. ...

 

Does this mean you could fit a switch to a cable to the Haldex and turn off 4WD (in theory at least - It's probably a digital control signal that a computer switched off...)? You'd have thought VAG might have provided a button for that for the few occasions when you want to turn off 4WD (eg MOT station equipped just with front rollers etc). Would be good for demo'ing 4WD abilities too!

[TeflonTom]

You don't need to turn off the haldex for mot brake rollers... But you can just pull the fuse out if you need to switch it off, also it won't engage when the handbrake is on either so you can just pull it up one click enough for the handbrake light to come on to disable it.

[Smokeyjoe]

We're not talking a £20 Argos trickle charger, the alternator on most vehicles will give out at least 80 amps on full field duty, between 5 and 8 miles it will be fully charged, I've even proven this before with a deep cycle drop tester.

 

I think you will find that the amperage is per hour that it is charging. An alternator may well start off at 80amp hours but will soon drop down. To fully charge a battery will take more that 10 minutes if it is flat.

[Vrstdi estate]

The reason I was concerned was from seeing horror stories on here of £1k - 2.5k costs of putting Haldex problems right and the car's warranty ended 4 months ago...... What surprised me if there was a failure was that the car has only done 31k miles with full dealer service history.

 

I use my Triumph Explorer most of the time so the car can sit for days without being used and even then it may only get a short run to pick the kids up.

 

Anyway, I thought I would share this with you in case you experience similar issues that could just be down to a low battery.

[Norry]

Battery drained? What's the punch line? It takes less than 10 mins roughly to fully charge a discharged battery through just normal driving

 

So you have a 13 AmpHour battery in your car?  80 amps x 1/6 hour. 

 

Norry

[ejstubbs]

So is it the case that the Haldex will come back to life of its own accord if the battery is charged?

 

I ask because I have noticed my front wheels scrabbling for grip on a couple of occasions recently, and I wonder if this might be the cause?  I changed jobs a few months back and I don't use the car much for work these days, so my mileage has dropped quite dramatically and recently I've only been using it for fairly short journeys, so it's possible that the battery might have become a little drained.

 

I did 350 miles yesterday which should have charged the battery nicely, but it still seems to be spinning the fronts a bit pulling out of junctions with loose gravel on the surface (of which there seem to be a fair few down here in deepest Herefordshire).

 

I did mention the front grip problems to the dealer at its last service a couple of weeks back but they didn't report back with anything obviously related to it, apart perhaps from the tracking being a bit out of whack.

[TeflonTom]

you would need to erase the fault codes from the haldex controller

[ejstubbs]

OK, I think I should be able to see any error codes via Torque on my tablet.  I'll check tomorrow before we head back up north.

[ejstubbs]

Hmm, Torque didn't find any error codes.  Maybe my right foot is just getting heavier with age...

[Kenny R]

Hmm, Torque didn't find any error codes.  Maybe my right foot is just getting heavier with age...

Or your front tyres are worn.

[MacFadyin]

Had to change the battery last month as it wasn't holding a charge, only done 35000K  (about 1000per month..)

 

Is it worth getting diagnostics run? Everything seems OK although there is a slight turbo lag

[900000]

On a slightly side note: my Yeti had been sitting unused for a month last month after I came back from France. Around the end of week four I went to the car at night to get my passport out and noticed that the Leaving Home lights didn't come on. So that's another feature that stops working when the battery starts to get too low. Neat.

[ejstubbs]

Or your front tyres are worn.

 

The Haldex should still redirect drive to the rear wheels, though, shouldn't it?  Worn tyres or loose surface, it doesn't know the difference, it's all wheelspin/slip as far as it knows.

 

As far as I can see (not that I habitually stare at the instrument panel when trying to deal with unexpected lack of control of the vehicle) the traction control light isn't coming on when the problem occurs.

[Kenny R]

Yes the front wheels have to spin before the haldex redirects to the rear wheels. The front wheels don't normally spin unless on mud snow etc, or the front tyres are worn, hence my statement.

[muddyboots]

Yes the front wheels have to spin before the haldex redirects to the rear wheels.

Not true of Haldex Gen 4....

 

From standstill, or when the ECU detects sufficient throttle movement, drive to the rear is pre-engaged.

 

It's more of a pre-emptive system than earlier Haldex gens which waited for the fronts to spin before engaging the rear.

[muddyboots]

More info on the self study guide, a copy here:

http://www.freel2.com/gallery/albums/userpics/11383/tiguan_haldex_gen4.pdf

 

Page 19 describes different driving scenarios, and when drive to the rear is engaged.

[ejstubbs]

Interesting, thanks for posting that.

 

Starting or Accelerating

A high drive torque is required at the rear axle. The

valve closes completely and the contact pressure can

reach its maximum.

 

That might seem to suggest that, when pulling away from standstill, 100% of drive is sent to the rear.  I suspect what it actually means is that 100% of the drive available at the Haldex clutch is sent to the rear wheels.  Otherwise there wouldn't be any drive to the front wheels to make them spin AFAICS.

 

My car had a sevice just a couple of weeks ago and the tyres came back with a clean bill of health: three had at least 5mm, one of the fronts was down to 4mm.  Still well short of the commonly quoted recommended replacement tread depth of 3mm, let alone the legal minimum.  WIth 25K miles on the clock and winter tyres on for half the year, I'd have been surprised had that not been the case.  (I would say, though, that I don't find the Dunlop SP01s to be a particularly impressive tyre.)

 

That said, of course loose or slick surfaces will reduce grip.  What I'm still puzzled by is the way that the electronics seem to leave the fronts scrabbling for grip for an appreciable time - at least long enough for me to react and lift my right foot a bit - without intervening.  Maybe the system just takes a second or two to switch out of moving-off-from-standstill mode. Perhaps it needs to achieve a certain road speed before it goes in to normal driving mode.  But as far as I can remember, it didn't used to do this - so what's changed?

[Kenny R]

Interestingly the Haldex pdf above mentions front wheels spinning before Haldex engages.......

 

"Starting with Slip (On Ice or Snow) The all-wheel clutch is engaged when both wheels of the front axle spin. The rear axle takes on all of the drive force.
If only one wheel of the front axle spins, the Electronic Differential Lock (EDL) becomes active. The spinning wheel is braked and the drive force of the other wheel is increased. At the same time the all-wheel drive clutch is engaged and a large portion of the drive force is transferred to the rear axle."

[muddyboots]

Interestingly the Haldex pdf above mentions front wheels spinning before Haldex engages.......

Yes it'll still do that, but during other scenarios when it can sense a likelihood that front grip may be lost (such as starting from standstill or under acceleration) it will engage the rears without waiting for the fronts to spin.

 

The difference between Gen 4/5 and earlier versions (I believe) is that Gen 4/5 are more integrated with other vehicle control modules, so can use inputs from other sensors (eg speed of change of throttle position) to act before spin takes place, whereas earlier generations I think only compared wheel speeds - so spin had to occur before the Haldex reacted.