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Author Topic: Vacuum switch  (Read 11501 times)

Offline David Hall

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Vacuum switch
« on: February 26, 2009, 04:10:53 pm »
86K10
305
700R4
NP208

Can anyone identify this vacuum switch? The wires going to it are lt. blue and yellow? What does it control in the transmission?
« Last Edit: February 26, 2009, 05:54:35 pm by David Hall »
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Offline David Hall

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Re: Vacuum switch
« Reply #1 on: February 26, 2009, 04:16:24 pm »
I can't post pictures, File too large?
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Offline rockable

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Re: Vacuum switch
« Reply #2 on: February 26, 2009, 04:37:33 pm »
e-mail the file to yourself and select "make image smaller", or post the picture on photobucket and put in a link.
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'86 SWB Silverado

Offline Captkaos

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Re: Vacuum switch
« Reply #3 on: February 26, 2009, 05:04:18 pm »
This is a how to on shrinking a picutre small enough to upload to the forum using Microsoft paint.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=6428.0
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Offline HAULIN IT

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Re: Vacuum switch
« Reply #4 on: February 26, 2009, 05:43:40 pm »
Dave, Is it on the firewall above the right valve cover?
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Offline David Hall

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Re: Vacuum switch
« Reply #5 on: February 26, 2009, 05:55:59 pm »
No, I just modified my first post with the smaller pics.
Take a look.
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Offline enaberif

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Re: Vacuum switch
« Reply #6 on: February 26, 2009, 06:14:12 pm »
That doesn't look like a vacuum switch.

Where are those wires running to?

They must have something on either end.
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Offline David Hall

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Re: Vacuum switch
« Reply #7 on: February 26, 2009, 06:25:01 pm »
It has two hard plastic lines going in. And in the picture the wire connector has been unplugged
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Offline rockable

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Re: Vacuum switch
« Reply #8 on: February 26, 2009, 06:38:19 pm »
I believe that is the EGR Bleed Solenoid.
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'86 SWB Silverado

Offline David Hall

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Re: Vacuum switch
« Reply #9 on: February 26, 2009, 06:45:17 pm »
It pulls vacuum from a thermal vacuum switch on the front of my intake (not on the thermo housing) and also from the back of my carb. It does connect to the egr but the wires from the switch are part of the harness that connects to my transmission plug (pin D) yellow wire.
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Offline rockable

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Re: Vacuum switch
« Reply #10 on: February 26, 2009, 07:08:26 pm »
Read this.  I don't know the wiring harnesses intimately but I identified the solenoid off the emissions decal under my '86 hood.

http://www.asashop.org/autoinc/dec97/egr.htm
« Last Edit: February 26, 2009, 07:11:59 pm by rockable »
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'86 SWB Silverado

Offline David Hall

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Re: Vacuum switch
« Reply #11 on: February 26, 2009, 07:35:16 pm »
Not trying to troubleshoot the egr, I'm trying to find out what this switch controls in the transmission. Thanks for the link though. I figured out this much so far: power comes from brown wire off the fuse panel, goes through the brake light switch on the pedal and comes out lt. blue. The lt. blue wire (hot),lt. blue wire w/black stripe and green wire (dianostic) go through the firewall and connect to another harness. This new harness, connects to the low pressure vacuum switch behind the brake booster, vacuum switch in picture and on to transmission connector. Question is what does vacuum switch in picture (on right valve cover) have to do with my 86 700R4.
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Offline VileZambonie

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Re: Vacuum switch
« Reply #12 on: February 26, 2009, 07:48:18 pm »
The other end goes to the TCC solenoid.
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Offline David Hall

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Re: Vacuum switch
« Reply #13 on: February 26, 2009, 08:02:45 pm »
On the transmission plug I have three wires (Green / A, Lt. Blue / B and Yellow / D). In side transmission Yellow goes to TCC.
Lt. Blue wire is from my low pressure vacuum switch, any idea where it goes in the trans.
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Offline David Hall

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Re: Vacuum switch
« Reply #14 on: February 26, 2009, 08:05:47 pm »
So the transmission has two vacuum switches for the TCC?
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