What is this switch??? (Pic)

[crawdad]

Can someone identify this switch and tell me what it is for? The vacuum hose that you see running off the right side of it was just hanging loose and I can't find where it goes to. Can someone tell me where exactly the vacuum line goes to and what would be the result of it being disconnected. Thanks for your help.
P.S. Forgot to tell you it's my 86 Chevy C-10 with 305 engine, auto tranny and cruise. Thanks.

[MylilBowTie]

If I remember right I think it has to do with the transmission.

[84 400]

is it part of the emissions system? i know some one deleted it on my old 85 and i got one from the junk yead. does it go to that round ball on the drivers dide near the hood hing?

[crawdad]

I don't know where it goes to or if it's part of the transmission or emission system. The hose was just hanging down behind the dizzy. While I was looking just a few minutes ago, I found another hose that is loose. This one comes from the small switch behind the power brake booster and it looked like it ran from there to the passenger side of the engine, or at least in that direction. Neither have suction on them when the engine is running so they must run to a vacuum port some where?

[swervin ervin]

It's a ESC vacuum switch.

On LE9 engine equipped vehicles with automatic transmission a "tip in" vacuum switch is used. Its function is to provide a momentary contact closure (signal) to the ESC controller during a throttle "tip in" condition which then briefly retards spark timing to minimize knock. The switch contacts are normally open under steady engine vacuum conditions including no vacuum, and all brief increasing vacuum conditions. Basically the switch closes only during rapidly decreasing vacuum conditions such as that encountered on rapid throttle operation.

[crawdad]

Originally Posted by swervin ervin

It's a ESC vacuum switch.
On LE9 engine equipped vehicles with automatic transmission a "tip in" vacuum switch is used. Its function is to provide a momentary contact closure (signal) to the ESC controller during a throttle "tip in" condition which then briefly retards spark timing to minimize knock. The switch contacts are normally open under steady engine vacuum conditions including no vacuum, and all brief increasing vacuum conditions. Basically the switch closes only during rapidly decreasing vacuum conditions such as that encountered on rapid throttle operation.

Mike, where does the hose run to? Does it go somewhere on the transmission, or to a vacuum port somewhere?

[smashingchuck]

Originally Posted by swervin ervin

It's a ESC vacuum switch.

On LE9 engine equipped vehicles with automatic transmission a "tip in" vacuum switch is used. Its function is to provide a momentary contact closure (signal) to the ESC controller during a throttle "tip in" condition which then briefly retards spark timing to minimize knock. The switch contacts are normally open under steady engine vacuum conditions including no vacuum, and all brief increasing vacuum conditions. Basically the switch closes only during rapidly decreasing vacuum conditions such as that encountered on rapid throttle operation.

sometimes known as a voes (vacuum operated electronic switch) and mostly kicks in during mid range accleration

[mhicks]

Looks like the vacuum switch for the lock up on the torque converter. It needs to connect ot the intake. It unlocks the torque converter after the transmission is in fourth gear and you get it under a load like when going up a hill on the highway.

[shadetree pro]

i got this same empty switch, i aslo have a vac line comming from my trans, that was hooked to the carb, but for what reason, i don't know. my edelbrock owners manual says nothing about a line to the trans., i think i'm gonna hook the the line to this switch, see how it goes. i'm trying to pinpoint 2 problems right now, 1 i think is just timming, the other is a stall under heavy acceleration, i think might be a vac problem like this. i guess we'll see, i'll let you know if it works.

[mhicks]

When I installed my 700R4 I installed one of those. The electrical part of it goes to the tranny. It is just a switch. The vacuum line goes to the intake. I connected 12 volts from my fusebox to a normally closed brake switch then to the vacuum switch on the firewall and then to the tranny. The 12 volts goes into the tranny to a 4th gear pressure switch so when it is is 4th gear it applies voltage to the torque converter. If any of the switches are opened then the converter can't lock i.e. brake is pressed, motor under load while in 4th gear or the tranny isn't in 4th. If any of these conditions exist then there is no power to the converter so no lock-up.

[shadetree pro]

i am thouroughly cornfused. i'm runnin a th350 trans in my '84, and i have NO electric connections, at least none that i can see. i have a passing gear cable, two cooling lines, spedo, and this unknown vacuum line coming from the rear, pass. side, before the tail. it comes out of a brass diaphram. i also do not seem to have a fourth gear, i run 3500-4k rpm at 70mph. i don't know if the 2 are related, or maybe i just got an old trans, or what, but i don't have the time(or gas) to drive around and check for changes right now, i could get some pics later though.

the line is kinda mangled, like it was reworked, it's soft line coming out of the trans, than to a hard line that ends before the back of my carb, than it is soft that was running to my carb, drivers side vacuum port. sure would like to figure this one out.
:tj: sorry

[MylilBowTie]

That is your vacuum line for the modulator valve (brass diaphragm). If you have a stock th350 it should be a th350c (lockup torque convertor). There will be a square plug on the drivers side around the middle above the trans pan. Could of had the transmission replace at one time and they used an older non lockup th350.

I can take a picture of it if you need.

[Slonaker]

Shadetree pro:

Your TH350 does not have a 4th gear because it is a 3 speed. If you don't have vaccum to the modulator, it will shift hard, and at odd times. At least that's what mine did once when I forgot to hook it up. Hook it to the vacuum tee at the back of the intake.

Like Mylilbowtie said, it will have a plug on the left side if it has a lockup (TH350C)

Slonaker

[swervin ervin]

The photo above is NOT a low vacuum switch for TC lockup. It's a ESC vacuum switch as I stated. The low vac switch for the TC is located behind the brake booster. The switch pictured is located on the passenger side firewall, where the ESC vacuum switch is located.

All the vacuum switches on these trucks were hooked to engine vacuum through a TVS with multiple ports to route vacuum to different areas, controlled by engine temp. The TVS's were located in the intake or thermostat housing. In other words, no vacuum is supposed to be supplied to said switch until the TVS tell's it to. I can't remember off hand which port it was supposed to be hooked to on the TVS but you should have a diagram on your radiator support showing all the vacuum hose routing.

Mike

[crawdad]

Thanks Mike. I also found the low vac switch for the converter unhooked as well. I have found one empty vacuum port on the TVS. I missed it before because it is buried underneath about 3 or 4 other vacuum hoses. I am assuming (which is dangerous) that the hose for the ESC switch goes here. Unless the low vac switch for the Tc goes here also, I just can't find another port anywhere for it. Maybe there was a "T" somewhere in the line??? I can't hook either of them up yet anyway, as it appears there is an adapter missing on the TVS for the hose to hook to. Appreciate your help. At least I now know what the hoses are and where they go. Thanks.