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Author Topic: Anyone know what these are for?  (Read 3342 times)

Offline Sprinkler-Man

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Anyone know what these are for?
« on: September 19, 2017, 09:51:09 PM »
1980 GMC Sierra Classic step side 4x4
I found these items disconnected by the brake booster when converting my brakes from vacuum to hydro boost. Know what any of them are for? I have attached a drop box link for pictures.

https://www.dropbox.com/sh/842y3mgifmhvfyi/AACSamjr-IyUHmhP1e4AJCuXa?dl=0

Thanks,
Dewayne
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Offline Smitty31

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Re: Anyone know what these are for?
« Reply #1 on: September 20, 2017, 05:09:40 AM »
The wire with the 2 green prongs plugged into the orginal carb beside the accelerator pump. The first pic with the vaccum connection may have something to do with the transmission . If not someone chime in and let us know I have it on my truck as well.The second pic I don't know.
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Offline VileZambonie

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Re: Anyone know what these are for?
« Reply #2 on: September 20, 2017, 06:37:07 AM »
Low vacuum switch. The other one that looks like the one near the booster is the tip-in vacuum switch. If you search the forum there are many posts on this.
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Offline Smitty31

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Re: Anyone know what these are for?
« Reply #3 on: September 20, 2017, 10:11:01 AM »
Ok I will look. What's the purpose of the low vaccum switch. Thanks
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Offline Smitty31

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Re: Anyone know what these are for?
« Reply #4 on: September 20, 2017, 10:19:47 AM »
Ok I searched this forum for low vaccum switch and found nothing. Also searched the Web and found nothing. It seems some people refer to these switches as tip in switch but again I searched both with no results. :(
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Offline Smitty31

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Re: Anyone know what these are for?
« Reply #5 on: September 20, 2017, 10:34:18 AM »
Ok the more I look the more confused I become. My truck is a 1986 custom deluxe 4.3 L AT wo/air no over drive 4 bbl and the distributor has a vaccum advance. So I have no idea what it is or if it works or how to test it.
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Offline VileZambonie

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Re: Anyone know what these are for?
« Reply #6 on: September 20, 2017, 11:41:06 AM »
So your truck is an 86 C10, 4.3L, THM350C, 4BBL? Is everything stock and connected? Is the VECI label in tact? What is the problem you are having? Most guys eliminated the connections over the years to avoid TCC in and out and erratic engine speeds.
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Offline Smitty31

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Re: Anyone know what these are for?
« Reply #7 on: September 20, 2017, 03:13:57 PM »
Everything is orginal sticker is intact but I have a turbo 400 transmission. It runs fine I just want to know what it is for and why I have it since I don't have overdrive and I have a vaccum advance not electronic.  And how do you test it? Also did you say it's best to understand plug them?
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Offline Smitty31

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Re: Anyone know what these are for?
« Reply #8 on: September 20, 2017, 03:21:42 PM »
Lol unplug them
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Offline VileZambonie

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Re: Anyone know what these are for?
« Reply #9 on: September 20, 2017, 03:25:53 PM »
Post a pic of your veci label.
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Offline VileZambonie

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Re: Anyone know what these are for?
« Reply #10 on: September 20, 2017, 03:26:19 PM »
and does your truck have cruise control?
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Offline Smitty31

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Re: Anyone know what these are for?
« Reply #11 on: September 20, 2017, 04:49:32 PM »
No i do not have cruze control. i took a pic but when i try to post it saids file exceeds 500 kb its just one pic,
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Offline Sprinkler-Man

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Re: Anyone know what these are for?
« Reply #12 on: September 20, 2017, 10:47:24 PM »
I thought the vacuum picture may be for the vent doors since they are vacuum operated. The original transmission was a TH350 but the vacuum modulator was connected to a port on the backside of the carb already.   
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