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Author Topic: vacuum switch attached to brake?  (Read 3866 times)

Offline jman340

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vacuum switch attached to brake?
« on: May 13, 2013, 01:49:55 pm »
Just got my 86 GMC 1500 back on the road, but still have the dash pad and other dash pieces off. I noticed a vacuum sound when I stepped on the brake, and looked under and noticed a vacuum switch attached to the brake petal. What is this, and should I be hearing it?
Thanks
John
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Offline zieg85

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Re: vacuum switch attached to brake?
« Reply #1 on: May 13, 2013, 01:58:35 pm »
It disengages the cruise control
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Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline Boone83K10

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Re: vacuum switch attached to brake?
« Reply #2 on: May 13, 2013, 03:16:48 pm »
yes it is cruise. I tried to take my cruise off and I lost converter lockup.
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Offline jman340

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Re: vacuum switch attached to brake?
« Reply #3 on: May 13, 2013, 06:31:29 pm »
I'm guessing it shouldn't sound like a vacuum leak. I no longer have cruise, so can I just cap the line to it, or will that disable the converter lock also?
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Offline frotosride

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Re: vacuum switch attached to brake?
« Reply #4 on: May 13, 2013, 07:45:57 pm »
Quote from: jman340 on May 13, 2013, 06:31:29 pm
I'm guessing it shouldn't sound like a vacuum leak. I no longer have cruise, so can I just cap the line to it, or will that disable the converter lock also?

It will disable lockup because the vacuum switch is part of the lockup wiring.
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Offline zieg85

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Re: vacuum switch attached to brake?
« Reply #5 on: May 13, 2013, 08:21:56 pm »
Your vacuum power booster may be what you are hearing.  Disconnect the vacuum to the booster and determine if you still hear the hiss.
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Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/
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