McGuireV10

Yesterday a friend told me about a switch or relay under the gas pedal which you can feel "click" when you fully depress the pedal (WOT). He has a C-class and was asking me if the E-class has it.

We found a suitably open spot and I gunned it, and sure enough, when the pedal is on the floor, you can feel a "click", and after a second or so it pops back (which is why I say it's probably a relay and not just a switch -- splitting hairs I guess). It feels little like those old foot-operated high-beam switches they used to use in trucks and vans (or maybe they still do, I don't know).

I want to say I felt the transmission kick down as I clicked the switch, but it was all coincidental with accelerating fairly fast anyway, so I'm not sure if the switch did that or not.

Anybody know what this is or what it does? I did a quick, somewhat lame search for "gas pedal switch" and found nothing...

DWP

http://www.autopartsworld.com/merced...itch_part.html

If the W211 doesn't have a kickdown switch, it could be because M-B replaced a mechanical switch with software that reads accelerator position and other variables to decide when a downshift is needed (but I really don't know).

In high school I drove a '50 Ford Convertible (slightly younger than me) with a foot-operated high beam switch, not that it made much difference with a 6-volt electical system.

SAguirre

My 190E 2.3 -16 did not have that switch because it was a stick shift. My 1991 300E definitely had it and you needed to press it if you wanted full acceleration. When you pushed that switch you better be prepared to feel a kick and the engine would pull like mad!

I spoke with a MB engineer years ago and he told me that the purpose of that is eliminate any doubt about you wanting full acceleration. By pressing that switch with the pedal, you are telling the system you need all it has to offer. This was sometimes needed on the Autobahn. When I get into other automatic transmissions, I get startled when the car kicks down to really low gear and the engine revs like mad WHEN I ONLY HAD THE PEDAL 1/2 way down.

This switch is still there on the W211, but it is totally computerized (needless to say). It is still a method of telling the computer you really want full power in throttle and gear.

I like this feature in Mercedes. It makes it very clear that you can floor the pedal and the system will know what to do. In most GM and Ford cars, I find that the throttle is not proportional and that the last 1/2 of the pedal is useless (most of the time).

Just my opinion,

Steve

vraa

My X5 4.4i MY2004 has it.
My old LS400 MY1994 had it.
My dads SL500 MY2003 has it.
My moms LS430 MY2005 doesn't have it.

It's the kickdown button. When you depress it, the tranny knows to kick down a gear to throw you into a better torque range for passing other cars.

johna1

As already stated it is the kickdown button. It is a feature of every auto transmission I have ever heard of, although if you say it's not on the LS430 I'll believe you!

If you don't already know about this, then you are driving cars that are too powerful, or driving too slowly!

I had an Jaguar XJS where this didn't work, and the first time I pulled out to pass someone and put my foot down, and it pulled away gently in top gear I just about died of fright.

It is there to tell the transmission to shift down to the lowest feasible gear. I guess now with the intelligence in gearboxes (and the fact that not everyone seems to know about it), it almost makes sense to get rid of the physical switch and replace it with an accelerator position sensor.

Except, the downshift can be quite abrupt when it drops from, say 5th to 2nd, so a physical detente makes sense to ensure that the driver really wants this behaviour, otherwise I can see all sorts of complaints about jerky transmissions!

SAguirre

Well, most US cars don't have that switch. GM and Ford cars tend to have a very touchy throttle that fools you and makes you think that the car has tons of power, but after you push the pedal more you realized that there is nothing there. As a result, I find that US model cars sometimes downshift prematurely (especially if you are used to this feature).

When friends of mine who only drive GM products drive my Mercedes they do not think it has a lot of power because they are used to that jump at the beginning of the throttle along with the downshift/kick down between 1/2 and 3/4 of the pedal travel.

I find the German gas pedal to be very good. It is very easy to accelerate smoothly and it is very easy to really rip it up. Mercedes and other better car brands know that the throttle's travel should be used completely. I personally like that!

Steve

vraa

I like the LS430/400's or the SL500's throttle more then the X5's.

First gear in my truck just sucks. It's too touchy for off roading and too short to accelerate decently. It just goes:

VROOM *shift* so you're jerked very hard when it accelerates off the line, and then jerked again because the engine bounces off it's rev limiter.

I have to use manual mode and let the tranny shift itself into third when I come to a stop. BMW's manual mode doesn't shift lower than that.

johna1

I hate to be argumentative, but every US car I have driven has had a kickdown switch.

Admittedly, I haven't driven one in the last 5 years or so, but prior to that they all seemd to. Are you sure you've just never found it? After all, you didn;t know about the one in your E!

SAguirre

I don't know who you are referring to here, but I personally only noticed a kickdown switch in a few GM cars. The switch might be there, but it is useless since the car downshifts much too soon anyway.

Steve

McGuireV10

I've never noticed it in any other car I've driven, although truth be told I prefer manuals.

JimPurdy

I haven't noticed any switch in my O3 E320.

konigstiger

Looks like a button, behind gas pedal up at top.

DWP

Son-of-a-gun, is that what that is? I thought it was the trigger for the passenger ejection seat. Serially, I must have vacuumed around there 20 times and never once noticed the button.

Brav

I know exactly what you mean! I get frustrated trying to explain this to countless numbers of people...

it works great for selling cars at the lot - people are a bit apprehensive to floor it with a salesman in the car, but to tap it and get a good response, people kinda go "ohh.. thats nice."

fools..

C_class

Because I have a manual c-class. I would like to know what is it function on manual cars?

rapidoxidation

From '02 on up, the button is just a clicky button that isn't connected to anything. No wires, no mechanicals. It just lets you know you've reached the bottom of the accelerator pedal's travel.

I know, double zombie thread. I'm trying to find answers to why my accelerator pedal will only push the engine to half power. I believe my sensor "B" circuit is wonky in the APPS.
2005 E320 CDI
codes: P0123, P2135, and P1222. There's also a P0673 code which I believe means I need a new glow plug on cylinder #3...

At full acceleration (at least, with my foot asking for it) in top gear, the transmission stays in 5th and the engine gently pushes along like I'm only giving it about half throttle. No kickdown of the transmission, no kick in the pants acceleration like I like. Sometimes. Other times it works just fine.

kaylib823

The w211 does in fact have a button behind the pedal a quick look in the owners manual will let you know that this is referred to as the Kick down button and is used to shift the the transmission down a gear for maximum acceleration

parato

I have a 24 450e. No question the pedal has a point of resistance when the gas engine comes on to help the acceleration. However, how long the engine stays on depends on how quickly and aggressively the vehicle is being driven. Software and other sensors are involved.