Miata Mailing List: October 1998, Message #7

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> From: "Bill Schnellman" <willschnell@hotmail.com>
> Subject: Power Window Switch again
> Date: Wed, 30 Sep 1998 14:07:02 +0000
> 
> Some time ago I asked all you nice people if anyone had problems with 
> power window switches not working.  Some of you responded, but 
> unfortunately I deleted the message.  Anyway, I took the switch apart, 
> and found carbon on the contacts.  I cleaned this off, put the switch 
> back together and everything worked fine, for a while that is.  The top 
> and window's have been down all summer (only comes out of it's garage on 
> sunny days)thus, very few cycles on the driver's window.  Last week, it 
> started getting cold in Minnesota, so the top was down, windows up and 
> heat on.  The driver's window again didn't want to go up right away.  
> Finally got it to work.  When we got home, I took the switch apart again 
> and the contacts were again covered with carbon.  Is there something 
> else I sould be doing after I clean the contacts.  I don't want to have 
> to take the console apart every few weeks to clean these switches.  Is 
> this just a defective design, or is is possible the motor may be pulling 
> more current than it should, thus the arcing across the contacts.  I 
> don't think a new switch is the answer, in that the contacts aren't 
> worn, just covered with carbon.  Thanks in advance for your 
> consideration.
> 
> Bill Schnellman

Bill:
I've not actually had to clean a power window switch in a Miata, but
have cleaned many other electrical switches.  To produce long term
proper operation after cleaning an electrical switch it's necessary to
clean the contacts extremely well.

High current (e.g., power windows) switching results in electrical
arcing at the switch's contact points.  Electrical arcing results in the
generation of carbon.  Carbon is a poor conductor that encourages
greater arching at the contact points and more carbon buildup.  

So, for long term operating life after cleaning it's necessary to clean
all the carbon away.  Carbon likes to live down within the pits that
form on high-current electrical contacts.  So, to get it all cleaned
away it's usually necessary to clean down within the metal of the
contacts.  Take some of the contact's surface metal away to remove all
the pits so you end up with very smooth and shinny contact surfaces.  

Arcing and the resulting carbon-buildup occurs more rapidly if the
switch's spring action is not quick and firm.  So, if possible in the
Miata's power window switches, tighten up the contact's snap-action
spring tension a little.  

When operating the switches press down quickly and firmly, and release
quickly -- this may help to extend the life of proper switch operation. 
 
When you cleaned the contacts before you may have left the contact
surfaces a little rough.  I'd suggest trying to clean the switch's
contacts once again, but better this time leaving very smooth and
totally pit-free contact surfaces.

You say "the contacts aren't worn, just covered with carbon".  Perhaps
it's not carbon and there is no pitting.  It might be that some
oxidation is forming -- the fix for that could be some mild cleaning
and/or just use the switches more often.  If the problem is oxidation it
may get better and better the more you use the switches.

These things I mention may, or may not be the specific problem in your
switches, but if they are, I hope it helps.


-- 
Jeff Anderson            @   @     @     @   @@@@@   @      
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