A Class 170CDTi W168 Semi-Auto Problem

[jonny h]

Hi Guys

Got a bit of a problem on my wife’s A Class, I’ve just got myself and new car and given the A Class to my wife.. anyway after a month the semi-auto gearbox has stopped working.

We have a W reg 170 CDTi with the Semi-auto gearbox, the one with the manual stick but no clutch.

All has been fine with the gearbox, but yesterday the car just stopped mid-journey with a F showing on the dashboard LCD display... the car will only start when you press the break peddle but will not go into gear, however when the engine is off the gears feel like they select fine.

Does anyone know of anything this might be... other than a mechanical gearbox problem.

Thanks

Jonny

 

[BlackC55]

Difficult one really.

Needs to be plugged into a Star.

 

[jonny h]

Difficult one really.

Needs to be plugged into a Star.

right ok off to the Merc place later i think

i've found something of intrest on another forum to do with a £10 repair on the ACS pump;

http://www.benzworld.org/forums/w168-class/1329207-semi-automatic-problem-no-clutch.html

 

[jblackCLK]

That was my post on the other forum. It definatly sounds the the autoclutch system as if it was the gearbox you wouldn't be able to select gears.

However the sudden onset of the fault leaves me wondering if it is the pump bushes.

In my case the fault came on over a few days ie the F appeared but a restart of the car got it going again for a short while. It quickly got worse until no amaount of hitting the passenger wing would get it going again.

Get someone to switch the ignition on and off a few times while you have your ear pressed to the passenger wing. You should hear the ACS pump priming (sort of mechanical whooshing). If all is silent then its most likely the pump or ACS ECU(expensive). Otherwise it is probably the sensors on top of the gearbox or again ACS ECU(still expensive)

Good Luck

 

[jonny h]

That was my post on the other forum. It definatly sounds the the autoclutch system as if it was the gearbox you wouldn't be able to select gears.

However the sudden onset of the fault leaves me wondering if it is the pump bushes.

In my case the fault came on over a few days ie the F appeared but a restart of the car got it going again for a short while. It quickly got worse until no amaount of hitting the passenger wing would get it going again.

Get someone to switch the ignition on and off a few times while you have your ear pressed to the passenger wing. You should hear the ACS pump priming (sort of mechanical whooshing). If all is silent then its most likely the pump or ACS ECU(expensive). Otherwise it is probably the sensors on top of the gearbox or again ACS ECU(still expensive)

Good Luck

Thanks Jonathan

Your post of the other forum looks intresting... stuck on my fridge door waiting for the weekend. I'll get my wife to try the ignition the car while I listen out for that noise.

The gearbox has been faultless until now.. fingers crossed it's just a simple fix.. the wife is already looking a new cars for her!

 

[jonny h]

Kind of have some good news, ACS pump looks to be the problem (maybe). I've taken the wing off and with a gentle tap on the pump the gearbox works for a bit and then after a number of gear changes the F is reported on screen... again a little tap on the pump fixes the problem.

I'm going to take a look at the pump tomorrow.. know of any other things i should be looking for.

Ta

 

[jblackCLK]

This definitely sounds like the bushes to me. You have done the hard work by getting this far. All you need to do now is take the casing of the motor mounted on the pump (smaller cylinder onthe side of the pump, two screws) and renew the bushes.

 

[jonny h]

This definitely sounds like the bushes to me. You have done the hard work by getting this far. All you need to do now is take the casing of the motor mounted on the pump (smaller cylinder onthe side of the pump, two screws) and renew the bushes.

Yeah all sripped down and the brushes are down to the wire and can no longer self adjust... just need to find a supplier.

Jon