53 plate 230slk direction indicator failures

[rmhodgson]

In April 2008 my direction idicators would on occasion stop working for no apparent reason. Function returned after parking up for an hour or two. Car was then under extended MB warranty. Problem diagnosed by MB as faulty control unit which was replaced and £883 invoice sent to warrant dept (phew).

It's now December - warranty expired in May - and guess what - indicators have spontaneously stopped working a couple of times recently but have resumed operation after a cool down period each time . IE exactly as before.

MB are syaing there's no warranty on warranty but if part is faulty MB may make a contribution.

Has anyone else come across this problem - is it a general problem with this model, is there a long term solution etc etc

Any pointer or a way forward to avid £800 pa for indicator maintenance would be appreciated.

Car is facelifted old model withn auto transmission and low mileage (~25,000 only) with full MB service history.

HELP !!!

 

[Cole@MBS]

the fuse contacts burn out, you need a new rotor switch, light switch!!!

 

[rmhodgson]

You could well be right as I have noticed that when indicators stop working then activating the light switch can reinstate operation.

Could you explain in abit more detail exactly what is happening here to I can enlighten MB who insist on repeatedly changing the control unit (three have now failed) - fortunately warranty has kept the costs at bay. The inconvenience and frustration is something else ...

 

[Cole@MBS]

New switch needed, the inside of the switch burns out on the fuse side!

 

[Uncle Benz]

Not just the indicators either! I have seen faults with intermittant brake lights and fog lights too with this unit. It is a bit more than just a light switch, as S-U points out - it comes complete with the fusebox.

 

[geoffd]

Re indicator fault

I have to disagree with the diagnosis here guys. I've had this fault with my 03 SLK 230, and while it's true that switching the lights on/off temporarily clears the fault, it's not necessarily because the switch itself is faulty. Usually when this occurs the bulb failure warning lights up as well, and although I can't explain the connection between the two events, they are related. The bulb failure monitor is part of the light switch and works by comparing left and right side circuit resistance.

This has been discussed on a couple of other forums too, and the suggestion is that a bit of dampness alters the resistance seen by the bulb failure monitor, which then causes the indicator failure. At the time I saw this on another forum, the fault was driving me mad - every time it rained I had no indicators. I was two days away from buying a new switch...

And the cure ? No, not a new light switch at £170 plus extreme amounts of aggro fitting it, simply removing the dash fuse box cover beside the light switch and spraying the back of the switch with an aerosol of water repellant electrical switch cleaner. 3 quid a tin from Maplin !

Try it - it worked for me and the fault has not recurred in 7 or 8 months.

Cheers

Geoff

 

[television]

I have to disagree with the diagnosis here guys. I've had this fault with my 03 SLK 230, and while it's true that switching the lights on/off temporarily clears the fault, it's not necessarily because the switch itself is faulty. Usually when this occurs the bulb failure warning lights up as well, and although I can't explain the connection between the two events, they are related. The bulb failure monitor is part of the light switch and works by comparing left and right side circuit resistance.

This has been discussed on a couple of other forums too, and the suggestion is that a bit of dampness alters the resistance seen by the bulb failure monitor, which then causes the indicator failure. At the time I saw this on another forum, the fault was driving me mad - every time it rained I had no indicators. I was two days away from buying a new switch...

And the cure ? No, not a new light switch at £170 plus extreme amounts of aggro fitting it, simply removing the dash fuse box cover beside the light switch and spraying the back of the switch with an aerosol of water repellant electrical switch cleaner. 3 quid a tin from Maplin !

Try it - it worked for me and the fault has not recurred in 7 or 8 months.

Cheers

Geoff

Well I think that on 99% of my replies I say use a switch cleaner (Maplins)
I have been using switch cleaners since 1950, the newer generation 1975 on are very good. Many circuits on a car are inductive, breaking an inductive circuit causes arcing and carbon build up, and metal transfer takes place on the contacts. These non drying cleaners prevent a lot of this. Even micro switches like those built into door lock clean up very well if caught early.

I think that I must have earnt more money from switch cleaner than anything else in my life

 

[rmhodgson]

That's more like it ...

Come to think of it my failures HAVE generally coincided with a spell of wet weather. I'm off to Maplin's tomorrow ...

If this works then the implication here is that MB have now swapped a £700 part (the control unit) twice even though it was never faulty in the first place!!

Rgds & thanks for the input - any more observations welcomed - I'll update with my experinces as they unfold.

 

[rmhodgson]

Where to put it ...

Thanks - visit to Maplins complete.

I presume I just spray over the fuse area - it's integral with the switch on mine so fuse area is effectively the back of the switch by my reckoning.

Is that right ?

 

[television]

You need to spray it into the switch contacts via the moving part

 

[rmhodgson]

Getting confused now ...

Geoffd states to remove fuse cover and spray back of switch

TV suggests from front via the moving bit

Any chance Geoffd (or anyone who knows) could clarify - am I cleaning the fuse contacts or the switch contacts and how do I best get to them please

 

[television]

Do the thing all over,,it will do no harm to anything, try and get it inside. And yes its very good for the fuse holder too.

I always have 5-10 tins in stock, it will not hurt anything, just wipe off with a rag any surplus

 

[geoffd]

light switch spraying

Sorry if I didn't explain properly.

As TV says, the object of the exercise is to get the cleaner/water repellant into as many of the nooks and crannys of the whole light switch/fuse box assembly. I'm not sure just where among this lot the bulb failure device is - but that's almost certainly what needs drying. I'm also fairly sure you can't spray too much - unless the excess starts to drip onto your accelerator foot !

The only other thing that bothered me a bit was the flammable warning on the aerosol. I'm guessing this is the propellant - probably butane or dimethyl ether - if so it's worth leaving the car a while for the fumes to clear from the confined space behind the dash before switching anything and maybe causing a spark...or worse.

Geoff

 

[television]

Sorry if I didn't explain properly.

As TV says, the object of the exercise is to get the cleaner/water repellant into as many of the nooks and crannys of the whole light switch/fuse box assembly. I'm not sure just where among this lot the bulb failure device is - but that's almost certainly what needs drying. I'm also fairly sure you can't spray too much - unless the excess starts to drip onto your accelerator foot !

The only other thing that bothered me a bit was the flammable warning on the aerosol. I'm guessing this is the propellant - probably butane or dimethyl ether - if so it's worth leaving the car a while for the fumes to clear from the confined space behind the dash before switching anything and maybe causing a spark...or worse.

Geoff

I think that the danger sign is only there as it has to be by law,, I am still with us and I use loads of the stuff in all conditions

 

[rmhodgson]

A big thank you

Many thanks guys for your time and attention.

I have duly sprayed liberally and am very hopeful that will be the end of it.

Although the explanations were not always fully complete they certainly are more believable - not to mention seriously cheaper - that the MB dealers approach.

I hope I can return the favour one day ...

Rgds

Roger

 

[Cole@MBS]

I still say you are going to have to replace the light rotor switch, done so many off them!!!

 

[geoffd]

changing light switch

You might be right that changing the light switch will cure this fault...simply because the faulty bit, ie the bulb failure device, is a part of the assembly. As far as I can see the light switch and the fuse box etc are all part of one big unit - see attached pic (which is left hand drive by the way !). The rotary light switch is the bit at the bottom pointing down toward the carpet. That amount of dismantling, plus the price of £170 secondhand is what persuaded me to find an alternative cure.

And since I sprayed mine I have not had one instance of indicator failure or any other evidence of faults in this unit. If burnt contacts was the cause, it would be getting worse and more frequent. I'm not convinced.

Geoff

 

[television]

We have a difference here of what you are allowed to do as a dealer. or what you can do as an individual.

Switch contacts can fail in many ways, the most common is when used on an inductive load. As the switch breaks contact,arcing will take place as the contacts part, this is due to the Back EMF in an inductive circuit. Most manufactures (not cars) fit a capacitor over the contacts where the cap charges up and cancels the back EMF.

When arcing takes place on a switch, several things can happen, the arcing produces carbon that can build up to a point where no electrical contact is made on the point contacts of the switch. The other thing that can happen is the the metal on one contact can transfer itself onto the other contact in the switch so that one contact gets smaller and the larger one bigger, this seldom causes a problem in a single pole switch, but on a multi switch with many positions if the transfer of metal goes from the wiper that has to make contact in all of the other positions, then contact will be poor, and this will create more arcing and one has to wriggle the knob to make contact.

When a non drying cleaner is used as against the cheaper variety that dry, the switch contact arcing is reduced and carbon that builds up, eventually leading to no contact is reduced to a minimum.

MB dealers are not allowed to do this and its replacement only, this was also the case when I did service in the UK for manufactures as well, I would clean where I knew that a good job could be done, if in doubt,I replaced

 

[geoffd]

i know we are getting off the subject here, but...

I'm not an electronic engineer, but...

Isn't a light bulb a resistive rather than an inductive load - or is it inductive because it's a coiled filament ? And even if it isn't resistive, doesn't inductance vary with frequency, so DC, ie as in car, applications should have little if any inductance ? So why does it cause contact burn ? Or am I missing something ?

And on a different subject, why are MB not allowed to use products like switch cleaners ? I'm not sure I see the difference between lubricating a switch contact and lubricating a door hinge. Both prolong the component life and reduce the need for replacement.

Anyone else with direct MB service knowledge care to comment ?

Geoff

 

[television]

I'm not an electronic engineer, but...

Isn't a light bulb a resistive rather than an inductive load - or is it inductive because it's a coiled filament ? And even if it isn't resistive, doesn't inductance vary with frequency, so DC, ie as in car, applications should have little if any inductance ? So why does it cause contact burn ? Or am I missing something ?

And on a different subject, why are MB not allowed to use products like switch cleaners ? I'm not sure I see the difference between lubricating a switch contact and lubricating a door hinge. Both prolong the component life and reduce the need for replacement.

Anyone else with direct MB service knowledge care to comment ?

Geoff

No a lamp is not inductive, but a relay is, or possibly something inductive in the lamp failure circuit. with relays often a diode is used to suppress any fly back, but there are problems in all of these things in that any form of suppression must be as near as possible to the source, to have any effect on that component or others in that circuit. Any relays are under the bonnet, and the controls are in the cab, so the length of the cable comes into it, for what happens one end, can be completely different to what happens at the other end. It is a specialized subject