Electronic vacuum switch? (700R4)

[Fairlane514]

There are two what look like electronic vacuum switches on the firewall of my 84 C10.  One on either side of the center of the motor area. The one on the passenger side has a two wire plug coming into it, and a single vacuum line out which then plugs into a "tree" at the back of the intake manifold. I believe this one has to do with the 700R4 lock up.

The other one is located just above the cruise control canister and again has a two wire plug coming into it and a single vacuum hose coming out. This hose has a filter on it and then it remains unplugged by the previous owner.  Does this also plug into a vacuum source?  Ported or full vacuum?  What is it for?

Both switches look similar to each other, so thats why I think they may be related somehow. 


Thanks in advance.

[bake74]

     Do you have any photo's.

[Fairlane514]

I can take a picture, just not sure how to download on this site.

[Captkaos]

There is a post in the tech section stickied at the top detailing how to upload photos to the forum.

[Fairlane514]

OK, I tired posting the picture, but It doesn't load the picture. i have a Mac so maybe it has something to do with that.

I will try and describe it again...........It is screwed to the firewall directly to the left of the brake booster in the 10 or 11 O'clock position in reference to the booster.   It is round with a vacuum hose coming out of the end facing the brake booster. On the opposite end is an electrical plug with two light green wires.  The round portion of the switch is surrounded by a light gauge metal bracket crimped on to it. The metal bracket is screwed to the firewall. The vacuum hose that comes out of it can easily reach the carburetor. 

It seems to me it has something to do with the transmission as it looks very similar to the other switch on the opposite side of the firewall which I believe has to do with the 700R4 lock up.

[HAULIN IT]

it looks very similar to the other switch on the opposite side of the firewall which I believe has to do with the 700R4 lock up.

Yes, the one on the Right side of the firewall dip is for signaling the lock-up feature of the torque converter. Sorry, can't help you on the one on the Left side. What color are the wires on that one? Lorne

[TexasRed]

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[Fairlane514]

The one on the drivers side has two light green wires plugged in to it.

I replaced the ESC distributor with a straight HEI from Summit.

[TexasRed]

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[HAULIN IT]

Texas, Do you have only the one on the Left or do you have the one on the Right also? Lorne

[TexasRed]

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[HAULIN IT]

I had both, the one on the passenger side (left) is now gone as is the ESC distributor.

We're car guys talking about parts...The passenger's side is the RIGHT! Doesn't matter if your standing in front of it, sitting on the tailgate or sitting on the couch in your living room. Anything on the passenger's side of a vehicle is the RIGHT. Lorne

[Fairlane514]

I know that's RIGHT!

[Fairlane514]

I went ahead and plugged the vacuum line from the switch into a ported source on the carburetor.  From some research I did, I believe it originally plugged into the tree on the thermostat housing. I have since removed the tree, so that's why I used the carburetor source.