500sl hardtop faulty

[dave hobbs]

Any ides on the following
Switch will not operate at all, will not lower windows,roll bar, release catches, no audio alarm. Windows and roll bar work 100% with their own switches. Roof switch lights up and goes off when ignition is turned on and does not flash showing a fault. Checked all fuses, released catches with roof tool one at a time to check light on switch would flash which it did but no adio alarm. The switch seems to do everthing it should regarding the flashing of the light etc but nothing works no noise even from anything trying to work. Maybe I have missed something. I would like to be assured that the soft top computer is ok (OR MAYBE NOT)obviously it works for the windows and so does the hydrolic pump in boot work for roll bar.

Many Thanks

Dave

 

[pascal]

The switch shouldn't flash when pulled back unless, low battery.

The voltage from your battery may be too low. Did you try it with the engine running, Gears in P, and parking brake on.

 

[dave hobbs]

Hi pascal
Thanks for the reply
The engine was running and in p Having the car for 4 years I am sure that the light always flashed when lowing and highering the roof, also I can't remember putting the handbrake on, not using the car very often I must be wrong. Do you think that the computer under the rear seat may be at fault personaly I think not because I can hear the electric windows click in and out from the computer box. "What do I know". From my tests in the previous question I can not understand why when using the tool to release the catches on roof to make a fault I get the flashing light but no audio alarm every thing is completly dead. Any ideas pascal.

regards

Dave

 

[pascal]

The light should stay on when opening/closing, not flash. My manual says flashing means low voltage.

The handbrake does not need to be on, or in P (just said that for safety). But it will not work when the car is moving (light flashes if you try).

I'm not sure what stops you moving it up/down when moving, but is probably the speed sensor in the wheel.(guessing). (could this be the problem?)

You say you've checked all the fuses. It still would be no harm to replace fuse 9 (i think) in the boot fuse box. Have you checked all the wires going to the roof CPU.

Could be a long process, sorting out, but's best to start at the simple (and cheapest) ones first.

 

[dave hobbs]

Still no joy seems like a visit to merc £££££££ unless anybody can sugest something else.

Regards

dave

 

[pascal]

High David.

Don't know a lot about how it all works. May get one of those DVDs on Ebay.

It seems to me, that when you press the red button it sends signal to main computer.
This main computer, sends signal to windows & rollbar control, before opening roof. It also receives signal to say car is not moving (wheel sensor), more signals from different sensors on roof mechacnism before and during open proceedure. After roof is stowed, it sends signal to window and rollbar control, to return it to it's original position.
Is this briefly what you think happens?
Suppose if one of these sensors is faulty, the roof won't work?
If you get the wiring diagram with signal amps for each input/output, you can find the fault with the aid of an ampmeter thingy.

 

[webby]

Hi Dave,

I had the same problem a while ago but my roll bar would not work and the one touch operation of the drivers side window would not work. In the end the dealer installed a new computer, although judging by their lack of expertise with my car I'm not sure it needed one.
Pascal is correct in saying that the roof is also connected to the speed sensors on the wheels, however I doubt it they are faulty because if they were sending a signal to the roof saying the car was moving they would trigger the audio alarm (I think it starts at anything over 5 MPH). I figure the first thing to try is get the computer reset by the dealer.....should only take about 10 mins and go from there.

If you want to have a go at reading the fault codes for the top it is quite easy using a few bits of wire a resistor and an LED. Have a look on www.benzworld.org there are a few tips on how to do this, I think itwas in the forum around july 2004.

Good Luck!

Thanks Pascal for the info on the light, mine flashes when I operate my top, I guess I might need a new battery.....you learn something new with these cars everyday!

Webby

 

[dave hobbs]

Hi again pascal

Thanks for your interest in this problem.
Do you mean the softtop computer under the rear seat or the main computer in engine bay ?
I agree what you are saying.
I can not get my head round the fact that if there was a fault with sensors that my roof switch would show a light flashing all the time. This is not the case the roof switch as no light in normal condition. As mentioned I can use the roof tool on all catches to show a fault with the light flashing. Please note no audio alarm sounding when in fault mode. Thanks again for your help and advice with this problem. Any other readers with wiring diagram please send it to me.

Regards

Dave

 

[pascal]

Bear with me for 10 minutes David. I have a probable solution to you problem related to your windows.

 

[pascal]

If there's a fault with the soft top (when fully open or closed) it will only flash when trying to open or trying to close.

Direct from Manual

If the indicator lamp in the soft top switch flashes when the switch is pressed:

• The battery voltage may be too low -- allow the engine to run.
• The drive may be overloaded (eg if it is operated about 5 times in succession) -- it can be operated again after about 2 minutes.
• The voltage supply may have been interupted (battery disconected or discharged) -- the soft top cannot be opened or closed. To close the soft top, first remove key from ignition lock, wind the soft top back into soft top compartment by hand and re-adjust the side windows, see Interior. Before opening the soft top, re-adjust the side windows, see Interior.

So what they are saying is to do a window reset. You know how to do that?

• Close window fully whilst holding button in the up position for over 2 seconds
• Repeat this on passenger side

 

[dave hobbs]

Hi pascal

That looks to be the trick hopefully. I will let you know tomorrow if it stops raining. If it works I will post a smiley face, if you see a grumpy face please still read my follow up text.

Regards and many thanks

Dave

 

[pascal]

The Mb instructions are a little confusing.
I'd try the window reset with the hood up first.

 

[dave hobbs]

Hi pascal

No joy.

Whilst pressing the window buttons and roof switch basicly just messing about I did get movement on windows with roof switch only for a few seconds I dont know what I did apart from just play with the switches the roof switch acted as the window button but only on the down position and one window only. The other window did do the same but at a different time. All the time that I have been playing about with this problem not once as the audio alarm sounded. I think I will have to do what webby suggested in an earlier reply and get it re programmed. If this is whats needed I am banging my head against a brick wall trying to solve it. Will keep you informed.

Regards

Dave

 

[pascal]

Well that sounds like you need to do the window reset.

Some times you have to hold the button down in down position for a few seconds and up in up position.
You have to do it with both windows, with their respective buttons.

 

[pascal]

This is another method that worked, doors closed!:

Try a reset first

• Quote:
  Originally Posted by pascal
  
  
  • Hold 'down button' down and for 5 seconds more after window has opened
  • Hold 'up button' up and for 5 seconds more after window has closed
  • Repeat first step
  Do interupt during either of the 3 steps
  This is the procedure for window reset
  

PS It might be an idea to have the windows fully up before starting. And start by holding 'up button' up for 5 seconds before comencing above.

 

[dave hobbs]

Hi Pascal
before I do another reset on the windows tomorrow, can you tell me if it is normal after holding the switch down or up for about 5 secs or slightly more that there is a slight delay before the windows power kick back in again. basicly it seems like a lock out for about 10secs before the windows work again after holding switch up or down.

Regards

Dave

 

[SLinKyjoe]

as i normaaly get some stick for having a baby slk....it says in the new manual to hold for 10secs at the lowering stage and then 10secs once the window has traveled all the way up.

 

[pascal]

Not sure Dave. Maybe 5 secs is too long. Mb says 2 secs.

The fact that the windows moved a bit today with the hood switch seems to suggest that that is the problem. The hood will not work until the windows are opened, so the hood computer must take some signal from the window computer. And the hood computer must also tell the window computer to open the windows before opening of the hood.
All I know is that the window computer has to be set before this comunication can occur.
BTW did you ever have a power interuption on the window computer.

 

[dave hobbs]

Hi SLinKyjoe
Thanks for the tip.
I have held button down for longer as well.
This is why in my last post I needed to know if it's normal for the windows to trip out and return to normal after about 10 secs.

Thanks for your interest

Dave

 

[pascal]

Well it says two seconds on my manual. May be different firmware (software) on different model years.

Personally, I would do a reset with the roof down, and whether or not it worked, another reset, with the roof up.

Maybe this is what resets the roof computer. In answer to your other question, Dave, I'm not sure.