C43 AMG Estate Cruise Control Problems

[Riorup]

Hi, I wondered if anyone can give me some advice, i bought a 1998 C43 2 weeks ago, very happy with the car generally, but the cruise control only works 50% of the time and even then sometimes drops out, and will not reset.

Similar behaviour from the speed limiter, (not that I want to use it).

I am planning a french holiday road trip so very keen to get it fixed but trying to avoid paying a garage!

Any help gratefully received.

Regards Rupert.

 

[FunkyFez]

I had a similar problem with my C43 and discoverd the problem to be the rear tyre profile was 45mm as opposed to factory fit 40mm. The cruse can also be effeced by incorrect tyre pressures (which should be indicated on the inside of the fuel filler flap).
I think it's to do with the speed sensors on the front and rear wheels giving mixed readings.
This is just my opinion but i'm sure there will be somebody else along in a minute with some additional advice.

 

[Will]

Do you get any errors at all?

I'd probably start by checking the tyres as already mentioned and possibly the brake light switch.

Will

 

[GordonTarling]

A different rolling radius between front and rear wheels will do this - even, for example, new tyres on rear and worn tyres on front.

 

[Riorup]

Thank you for the suggestions, the rear tyres were very worn, and i had also heard about the tyre diameter sensitivity, so i bought new rears at the weekend but the problem is still there (not sure if it has changed at all). I will double check the pressures just in case, but this seems really sensitive if it is the cause.

No errors have shown up (do you mean on the little display panel in the dash?)

Brake light switch? what am i looking for here?

(thank you for the replies everybody)

Regards

Rupert

 

[Shude]

No errors have shown up (do you mean on the little display panel in the dash?)

Brake light switch? what am i looking for here?

If the brake switch had gone then you'd have a red, ABS/BAS warning on the dash.

 

[Riorup]

No errors at all on the dash.

 

[BTB 500]

Thank you for the suggestions, the rear tyres were very worn, and i had also heard about the tyre diameter sensitivity, so i bought new rears at the weekend but the problem is still there

Are you positive it has the correct size tyres on (front and rear)?

There are various rolling radius calculators on the web you can plug the details in to e.g.:

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

(scroll down a bit).

 

[Riorup]

Thank you for the car-bible info.

The car has 225/45 R17 fronts, 245/40 R17 Rears, which seem to be correct.

I just went to the local garage and checked/reset pressures

LF was 30, RF 32
LR was 30, RR 30

Reset to 32 front, 36 rear.

On the 3 miles journey back to the office the Cruise worked, but surely this cannot be the answer, will see on 15m journey home tonight!

 

[Riorup]

On the 15mile trip home the cruise worked for the first 10 so i thought it was solved, but then it dropped out and would not reset.

So back to square one?

 

[GordonTarling]

I have heard it said that even different makes of tyre front and rear can cause problems. Maybe worth getting the fault codes read, before going much further on the goose chase!

 

[Riorup]

You make a good point, I might contact Autobarn near Kettering which is probably my nearest good independent garage.

(Although i was told that the cruise control system problems do not get picked up by the error system?)

 

[Riorup]

I have not yet had a chance to take the car into a garage, but i have noticed the speedo does wander a little, I just wondered if this might suggest a faulty wheel speed sensor, hence the cruise problem?

 

[BTB 500]

Sounds like a distinct possibility. Good luck!

 

[Riorup]

I have not managed to get the C43 to a garage to check out the cruise problem so will take the C240 to France instead, will post the fix to the C43 if and when i find it. regards

 

[Howard]

It's going to be a lot less fun driving a 240 through France as opposed to the 43 !!