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Re: brake light switch

Subject: Re: brake light switch
From: Bob Howard <>
Date: Mon, 25 Nov 2002 08:42:17 -0500
  There is a way to bleed the brakes that is supposed to keep this switch
problem from developing, but now that you have it, the book procedure may
not sort it out.
   Inside the switch is a little shuttle sort of thing. When pressures
are equal in both circuits, that shuttle stays centered and the light is
out. When pressures are unequal, the shuttle moves to the low-pressure
side and the 'normally off' switch closes and the light comes on.  
   So the task now is to figure out which circuit was low pressure
circuit and has the shuttle in its side of the switch.  Xray, MRI, other
portable tool handy? Probably not.
   What I have done is to get a trusty assistant ready and bleed the
brakes (if not already done) so that pedal is firm.  Then I would loosen
one bleeder on front circuit and have him press pedal while letting some
fluid out. See if light is off or on. If it's off, you're done. If not
off, try letting fluid out of rear circuit.  There may be an elegant way
to do this, but this messy, empirical method has worked for me.
> So back to the brake light - I recall there was some specific way 
> was 
> needed to bleed the brakes so the brake switch was centered in the 
> lines. 
> Does anyone know the trick to do this? Meanwhile, I'll be checking 
> all my 
> other electrical connections as the day progresses.
> David Councill
> 67 BGT
> 72 B

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