ASR

GrahamC230K

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Got a few questions about ASR.

Hard to search on this topic as most forums only allow 4 character words minimum to search on!


My understaning of ASR is that when wheel spin is detected it brakes the offending wheel and also cuts engine torque. Triangle in middle of speedo flashes. This is quite evident by a simple test if nothing else!

Now with the ASR switched "off", the triangle illuminates and does the same thing but ONLY brakes the rear wheels, does not affect engine power. This too I know to be true, the benefit of having squeeky rear brakes when hot - I can make mine squeek by booting it in 1st!

So all this thinking came about when my car was on a rolling road with a strap down system designed for no wheelspin on cars with far more power than mine but with my car, the ASR "off" the triangle fashed away the WHOLE time.

1. Did the car know the front wheels were not oving and hence assumed a traction problem?

I thought only ESR equiped car had sensors on the front wheels. But maybe ASR uses the front wheel ABS sensors to.

2. In a thread on benzsport this got posted by someone in the US from their owners manual:

If one drive wheel loses traction and begins to spin, the brake is applied until the wheel regains sufficient traction. The traction control engages at vehicle speeds up to approximately 25 mph (40 km/h), and switches off when traction is regained, up to 50 mph (80km/h).

The ARS warning lamp, located in the speedometer dial, starts to flash at ANY vehicle speed as soon as the tires lose traction and the wheels begin to spin.

This is interesting.

I know the light certainly comes on at any speed (have had mine activate going over hump back bridges at 80mph), but does it stop activating over 50Mph?
It seems this is the case on US market cars, but is it true in the UK (I know the do differ some times)?

I have checked the "Driving" section of my handbook and no such detail, but I am missing the "Interior" section, which may detail the operation of the indicator light.

Can someone check please?

thanks.
 
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Steve_Perry

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Originally posted by GrahamC230K
I have checked the "Driving" section of my handbook and no such detail, but I am missing the "Interior" section, which may detail the operation of the indicator light.

Can someone check please?

thanks.

Hi Graham,

The documentation for my car consists of 6 sections (7 if you include the factory fitted Audio 10 stereo).

1. - Service Booklet.
2. - Interior, Owner's Manual C-Class.
3. - Exterior, Owner's Manual C-Class.
4. - Technical Data Saloon, Owner's Manual C-Class.
5. - Driving, Owner's Manual C-Class.
6. - Radio Audio 10/30, Owner's Manual.
7. - mobilo, the Mercedes-Benz mobility package.

Here's all the references to ASR that I could find:

Interior, Page 24:
ASR warning lamp - Risk of accident!
If this (yellow triangle) warning lamp lights up in the speedometer:
Adapt driving style to suit road conditions.

If this warning lamp flashes in the speedometer:
Only depress the accelerator pedal as far as necessary when pulling away.

Ease off on the accelerator pedal when driving at a steady speed.
Adapt driving style to suit road conditions.
Do not switch off the road stability system.
If these warnings are not heeded, the car could enter a skid.


The book then goes on to explain BAS/ASR malfunction light and also refers the reader to the driving section for a more detailed explanation of ASR / BAS.

Out of interest, here's something I didn't realise before...
If the acceleration skid control (ASR) is faulty, it may be that engine output is reduced. :crazy:

Exterior: No reference, no suprise there then :p

Technical Data Saloon: No reference.

You said that you already have the Driving section of the manual so I won't regurgitate it verbatim here. In summary -
If the tyres reach their adhesion limit, the wheels are braked and engine torque reduced to enhance stability. The warning lamp in the speedometer flashes when this action is taking place.

De-activating ASR road stability system. Engine torque is then no longer limited and the drive wheels can spin, which may help them to cut into the loose or slippery surface. Traction control will continue to take effect if a single wheel reaches its grip limit, for instance if the side of the road is icy.....


I'd say that your not missing much with respect to ASR by not having the interior manual. However, might be worth trying to get one as there is a whole host of other useful info in there.

*EDIT* There is a paragraph in my Driving manual that is almost identical to the section that you quoted from Benzsport. Therefore I would say that our cars behave in exactly the same way as the US cars do. Let me know if you want a quotation from my manual.

Sorry I couldn't shed more light on the whole ASR thing though.

S.
 
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jimmy

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On my Vito van I had a problem with the traction control in that it did not work at speeds over 30mph. The light would flash but nothing would happen. The dealer said that the system is not supposed to work at higher speeds as it could cause damage to the brakes or wheels, so they said!

With a FWD unladen van with 122bhp you really did need traction control so it was a bit of a gimmick really, although it did help me out of a few muddy fields a couple of times.
 
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GrahamC230K

GrahamC230K

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A great help Steve.

I am going to call MB again about an Interior booklet.

However - my Driving one only has two brief paragrapghs - not all the detail you provided!

Very odd - more cut backs - saving on paper now.

So as my expalanation, and it sounds like it does not activate over 50mph.

To think all those times at high speed I have seen my lamp flashing and thought to myslef the car is sorting things out - and really it was doing nothing at all! LOL Me drives more carefully now.
 

Steve_Perry

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No Probs Graham,

You might find this site of use too.

To quote a bit more of my Driving manual, page 28:

This control system will cut in at up to about 40km/h (25mph). It switches off at the very latest at a road speed of about 80km/h (50mph).

The warning lamp in the speedometer will flash whenever a wheel reaches its grip limit, regardless of road speed.

If the vehicle is towed away with the front axle raised, or if the parking brake is being tested on a brake dynamometer, the engine must not be running.

If wheels with different tyre sizes are used, the correct operation of the ASR cannot be guaranteed.


Whoa I didn't know about that for brake testing either :crazy: One to remember for the MOT.

Graham, the reference on the back of my Driving manual is as follows:

Bestell-Nr. 6515 0026 02 Teil-Nr. 202 584 20 81 Ausgabe A

^^^Maybe worth comparing this reference to the one on the back of your Driving manual.

Hope this is more enlightening.

S.
 
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GrahamC230K

GrahamC230K

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Originally posted by Steve_Perry

If the vehicle is towed away with the front axle raised, or if the parking brake is being tested on a brake dynamometer, the engine must not be running.



Hmm, front wheels raised (ie not turning).

Makes me think that is why ASR trys to throw a wobbly when on a rolling road! Good job it gives up somewhere between 25-50mph!


MK MB trying to find me an interior section. Going to look at my Driving section again now.
 
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GrahamC230K

GrahamC230K

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Originally posted by Steve_Perry

Graham, the reference on the back of my Driving manual is as follows:

Bestell-Nr. 6515 0026 02 Teil-Nr. 202 584 20 81 Ausgabe A

^^^Maybe worth comparing this reference to the one on the back of your Driving manual.



The differences I think are due to me having a later revision of the handbook.

I am on 202 584 35 82 Ausgabe D
 

Steve_Perry

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Originally posted by GrahamC230K
The differences I think are due to me having a later revision of the handbook.

I am on 202 584 35 82 Ausgabe D

Seems weird that a later version of an Owner's Manual would contain significantly less information.
confused.gif


Beats me.

S.
 

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