what are the vac. switches to electrical connections on firewall?

[Swims350]

Well we have an 84 c10 with a 305 and th350 transmission in it.

Well I thought to be all original but the trans has no lockup and it has a TSC on it. So not sure of it's year.

It's a heat only truck and has the est dist. with the big 4 pin connector.

My question is what are the 2 vac. to electrical switches or connectors on the firewall? Ones over top the trans. dipstick and the other is over top the brake booster towards the pass. side.

What do they work? The DS one has vac. going to it from the port on top the thermostat housing and is still hooked up( I didn't remove it yet) I did unhook the other, and I unhooked the big vac. electrical switch by the trans. dipstick on top the intake. I got pics but have to get the pc to work with my camera.

I heard they are for est? but we had an 86 with the est and I don't think the vac. was hooked up to the pass. side one, I think it was cut and hanging, and it had no big one by the dipstick on the intake, and it had the one over the booster but not sure if it was hooked up or not.

I have yet to drive the truck after unhooking but what would happen if they are supposed to be hooked up? or what would they do unhooked now?

[VileZambonie]

One sounds like the low vacuum switch for the tcc solenoid. The other, I'd have to see a pic to know what you are talking about.

[Swims350]

ok here are a few pics from the other truck we had, it had the same hookups and kinda show you more since the motor is gone.

This is not the truck in question though.




This IS the trucl in question...





That was before things got removed. I got new pics just gotta get them on here which I should be able to do tomorrow.

Thanks for the help. Please help me further if you can, anyone.

[TexasRed]

Is it just me or is the edelbrock in the picture have the vacuum lines hooked to each other? The timed port and full vacuum? Good luck with an '84, I've got one and more dang vacuum lines than I know what to do with!

[Swims350]

the driver's side vac. in that pic was running to the dist. and the passenger side was a piece of vac. line about 3 inches long or less with a screw in it.

[Swims350]

back on topic here's more pictures up to date. of the truck in question.....



that'sd the pass. side one in question which vac. is now unhooked from, I unhooked it the other day, before then it was ALL hookd up.

The wires from that switch go down and tie into this one which is on top the manifold right by the trans. dipstick, here it is....



Then the other switch is here by the booster... which is still hooked up and I'll show you were it's vac. hooks up at after this pic.




That is the ported switch in the thermostat housing and I wonder if they need plugged off or not.



Just throwing out a pic of the engine lol.

[JJSZABO]

The one over by the trans dip stick has to do with the electronic spark control (ESC).  I removed mine when I switched from the ESC to an HEI distributor.

This is from Jeff's 73-87.com site:

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.
 

I don't know what the other one is.

[Swims350]

so is it gonna hurt to have them unhooked or to unplug them and lay the wires down behind the block or tape em out of the way, no cut anything just unplug.

[VileZambonie]

Are you not using the lock up feature in the trans?

[Swims350]

There is no lockup feature in the trans. apparantly it's been changed.

I know this because in the   catalogs the TSC is listed for like 76 and older trucks and shows a pic of the part going into the trans. and it's the same as what I have on the 84, also on the driver's side there is NO plugin on the trans for the lock up.

I can post pics of the TSC if you guys wanna see them.

[VileZambonie]

What are you referring too? Yes post pix. Since someone removed the original trans which had the lock up feature (either a th350C or Th700r4) you may as well remove it. However keep records of where everything went so if you decide down the road to hook up a trans with a TCC solenoid everything is right there.

[Swims350]

well I noticed a sender on the pass. side of the trans. and surfed around alot and founf out it's a tsc transmission spark control. It says in   it was only in like 73-76 or something but here's pics of it.










ok so which one can i remove then all of it or only the one? like I said the pass. side is unhooked right now, only one hooked up is the one by the booster you can see it and where it's hoooked up at in the pics.

[VileZambonie]

You mean TCS not TSC. Trans controlled spark. This was used to change vac advance to the distributor. You don't need to have it hooked up.

[Swims350]

my bad didn't mean to get it wrong, so which switch can be removed on the firewall or can all of em be taken out? I just want to make sure they don't go to esc or something and cause it to run like crap.

I want to unplug the 2 firewall switches, and the one on top the intake then plug the ports in the thermostat thing or put a plug in it's place and do away with it all.

[Swims350]

well looks like from reading and searching the one on the pass. side is for the esc and the tip in stuff for heavy throttle or whatever and sounds like it be fine if it's unhooked just maybe it might spark knock under hard throttle.


The driver's side one by the booster is for the lockup tc that is supposed to be in an 84 but isn't on ours. So that can be unhooked also, and I need to plug the tvs ports so it doesn't suck air or anything once open.


That all sound correct to you guys?