Re: LED Switch Failures

[steveb@newkla.kla.com (Steven Buchholz)]

I got this request from direct e-mail today.  My response bounced, but 
since there were others asking about this I decided to post it to the 
group.

> From wilsher@rap.ucar.EDU Wed Feb  1 16:33:12 1995
> 
> I saw this on the quattro list:
> 	I saw this on the net earlier ...
> 	
> 	Jeffrey Morgan said:
> 	> 
> 	> I find the decision to use switches that have LED's that can not be
> 	> replaced and force you replace the entire switch a bummer.
> 	> 
> 	> Are there any known fixes for replacing the LED's.
> 	> 
> 	The reason why LED's are not easily replaceable is because they rarely 

<Significant portion of my blathering deleted>

> 	also recommend that you burnish the switch contacts with some fine s
> 	andpaper while you're in there.
> 	
> 	Hope this helps
> 	
> Do you have any pointers/hints on _how_ to get the %^&*( switches apart?
> I spent last night trying to get one of these (electric window switch,
> Audi 90) apart, with no success. Does it take "just" a lot of prying, 
> or are there any other tricks involved?  I believe these switches are
> glued, too.
> 
> Thanks,
>      thomas
> 
> 

Well Thomas ... I'm hate to tell you this, but the switches will not look 
the same after the operation as they did before (at least mine didn't).  I 
actually dug out the extra switch I had and brought it with me today.  The 
part number listed on the bottom of the switch is 443 959 855C.

As you suspected, the black outer housing is quite securely glued to the 
inner (blue) portion of the switch.  If you have a problem with bad con-
tacts, they can be accessed from the long side of the switch that has 3 
contacts (numbered 3,4&5).  It does not appear that the bottom half (at 
the connector) is glued, so you might be able to carefully slice through 
the black plastic at the corners and remove the entire side of the cover.  
Once the side has been opened two sets of switch contacts will be visible.  
They are close to the connector end of the switch, so you don't need to 
remove more than about half of the side from the connector end.  I made 
a quick diagram below:

  Bottom View
________________
|         3    |
|       =====  |
|    1         |
|  =====       |
|         #    |
|         # 4  |  <== Switch contacts accessed from this side.
|    2    #    |
|  =====       |
|              |
|       =====  |
|         5    |
________________

View from switch contact side (after the side has been removed)

##########################
  ######################
  ######################
  #         ##         #
  #  ____   ##   ____  #   <== Fixed contact
  #  -==-   ##   -==-  #   <== Moving contact
  ######################
  ######################
    |      ####      |
    |      ####      |     <== Connector
    |      ####      |

You can get some fine grit sandpaper or an emery cloth and clean up the 
contacts at this point.  I actually hooked the switch up to the car and 
tested it while I was burnishing the contacts.  On one switch I had to 
move the fixed contact around with needle-nosed pliers.

Now that I'm looking inside the thing I can see that the LED is not on a 
printed circuit board, there's just an LED and current limiting resistor 
hanging inside!  If you have problems with the LED it would probably be 
pretty tough to get in there to fix it without totally disassembling the 
switch.

Best of luck on your quest!
Steve Buchholz