brake switch for lock-up

P

plcguru

Member
Joined
Aug 21, 2008
Ok, as per my previous thread about the best way to lock-up the converter I'm taking the advice there and using a TH400 1Pin connector & the N/O 4th gear pressure switch.
I'm also going to wire through the brake pedal switch to unlock when I apply the brakes.

In researching the brake pedal switch thing, I found most people just add a N/C relay to the switch... since the brake switch is N/O. Then when you step on the brakes the circuit relay contacts open and unlocks the converter.

Another option I found was to use a brake switch off a 1980's GM car (like the Buicks here :biggrin: ) that has cruise control. Evidently, that switch has 2 sets of contacts... one set N/O for the brake lights on the bottom and the other N/C on the side for the cruise control.
That may be perfect for my application which is a 1966 chevelle.... but I'm not sure if the diameter of the switch threads are the same. I circled what I mean in the picture below.

Anybody know the thread diameter circled for the Buick... of course my local autoparts stores don't have any in stock so I can see them and I'd hate to order one just to find out it doesn't fit.

cruise.gif
 
The cruise control uses a seperate brake switch with a vacuum release valve in it. What you use is the normal brake switch for the G-body cars with electronic TCC lockup. The car does not have to have cruise control. 82' up I think. Just for your info. :)
 
mikestertwo said:
The cruise control uses a seperate brake switch with a vacuum release valve in it. What you use is the normal brake switch for the G-body cars with electronic TCC lockup. The car does not have to have cruise control. 82' up I think. Just for your info. :)
Click to expand...

Good info, thanks!

SSedan64 said:
Hi again, These guys should be able to tell you the switch thread Dia. They have them in stock. They have the 4-Pin pigtails also if anyone needs it instead of the TH400 1-Pin plug.
eBay Motors: TCC / Brake Switch Conversion Kit (TPI, LT1, LS1, LSX) (item 170231424151 end time Jan-16-09 09:51:53 PST)

eBay Motors: 700R4 CONVERTER CLUTCH PIGTAIL CONNECTOR (TPI TBI) (item 170293078465 end time Feb-08-09 04:05:15 PST)
Click to expand...

The thread diameter was the same as I am looking for and he said the 2 sets of contacts were N/O and N/C. Should work then. Thanks
 
How do you wire in this new brake switch? I'm working on a 56 Belair.

I think the two rear terminals would be for the usual brake lights that are on my orig. two terminal brake switch.

But what do I plug into the three in a row terminals? I would like to incorporate an L.E.D. to indicate when I'm in overdrive.

Thanks for any help.
 
here's how I plan to wire everything using the ebay linked parts in this thread and the other. (2, not 3 connection switch)
I don't physically have the switch yet... but I believe the side is N/O and the bottom N/C... I'll confirm when it arrives here. If you don't use the same switch, put a meter across the terminals and see which is which on yours.

You can put a light in between the case connector and brake light switch to indicate it's in lockup if you want.

lockup.jpg
 
That is a great diagram, but I'm not that electrically talented.:redface:

My TCI kit has a 2 connector 4th gear pres. switch, and the stock 4 wire plug coming from trans, not 1 like yours.

I see now it CAN be done without a vac. switch. Can't understand why TCI told me different.
 
I finally found some time to work on my car and came across some issues, hopefully someone may chime in to help me out.

I'm using the 1987 Turbo Buick brake switch as pictured earlier in this post.

I found the two terminals to operate my brake lights, no problem there. What I'm doing now is to hook up the lock up part.
12V + keyed source to one side of 12V LED indicator light, other side of LED light to which brake switch terminal? (there are two sets of terminals, 3 posts and 2 posts).
Black wire from trans plug to ground, and confirmed good ground. Green not used.
I'm working on a 56 Belair with a 200-R4. When I press the brake pedal, I can't get the LED lit up and can't hear anything clicking in the trans. I hope I explained everything o.k.

Any help would be great!
 
210 Sport Coupe said:
I finally found some time to work on my car and came across some issues, hopefully someone may chime in to help me out.

I'm using the 1987 Turbo Buick brake switch as pictured earlier in this post.

I found the two terminals to operate my brake lights, no problem there. What I'm doing now is to hook up the lock up part.
12V + keyed source to one side of 12V LED indicator light, other side of LED light to which brake switch terminal? (there are two sets of terminals, 3 posts and 2 posts).
Black wire from trans plug to ground, and confirmed good ground. Green not used.
I'm working on a 56 Belair with a 200-R4. When I press the brake pedal, I can't get the LED lit up and can't hear anything clicking in the trans. I hope I explained everything o.k.

Any help would be great!
Click to expand...

Did you purchase an LED meant for 12v DC? Does it have a + or - label on either terminal/wire?
What terminals of the 5 on the brake switch are you connecting the trans to?
 
The two post set are the ones I'm using for the brake lights and work well.
I'm using the set of three in different arrangements for the LED and it is for 12V.
 
you first have to figure out the + on the LED. Is it marked?
Or connect 1 lead to +12v and ground the other. Does it light? if not, reverse leads and it should. Now you know which is +/- for the LED.

Now you need to know which of the 3 terminals on the brake switch are Normally Closed. Check with a meter... or if you don't have a meter use the LED from above. Connect the + lead of LED to +12v and the other lead to the left (of the 3 leads)brake switch terminal. Connect the middle terminal to ground. Does the LED light? If so, press the lever of the switch. Does it turn off? If yes, you've found the correct terminals of the switch. Otherwise, try other combinations, one combination will work. If none do, try using the switch in the drawing in the posts above.(it comes from rockauto.com search for part number sls159t $5.08 +shipping)

Once we know the above is correct the remainder in the trans itself can be checked
 
When I try this out on Monday, and the engine is off. Is it possible to hear the solenoid in the trans click or anything so I know it's activating the TCC solenoid?
 
nope, assuming you have the proper 4th gear switch as in the picture (i hope you checked it because I know mine was N/C which is the wrong one and needed to be changed...) the solenoid will not do anything until the trans is in 4th gear.
Did you check the 4th gear switch already?
 
Today's results....
With the brake switch installed, I used the two larger contacts from the set of three on the switch only to operate the brake lights, works great.
The one not used is the narrowest one.

As for the trans lock up, 12V + switched goes into one of the pair of contacts on the brake switch. The other contact from the switch goes to the red wire to trans plug A and + side of LED, ground other side of LED.

When the ignition key is on, LED is on, when the brake pedal is pushed, the light goes out and the brake lights come on. The switch in the trans from the TCI kit is N/O.

So I think I've got it, sound right to you?
Car is not ready for a test drive yet.
 
Almost... but not quite there. What you have now is the brake switch turning on/off the LED regardless of the solenoid.
Do you have D (black wire) going directly to ground? It needs to.

If you want the LED to indicate the TC is locked you need to have it in the circuit. So, +12v to one lead of LED and other lead of LED to the brake switch terminal where you now have +12v connected to.

Like this for the TCI kit you are using:
led.jpg
 
Yes, all this time I had D terminal (black wire) from trans plug directly to ground. May have not mentioned earlier.

B wire (green) not used.

In your diagram, you show the LED infront of the brake switch, where I have one lead after the switch and the other LED lead to ground.

Having the LED after the switch would show when the power is to the trans, and when it's off (brake on), having it infront of the switch, that side is always 12V + live.

Am I wrong ??:confused:
 
using the way you wrote won't do what you want because... if you connect one side of the LED directly to ground you are simply showing whether the brake switch is on or not. The status of the solenoid doesn't matter then.

The green line shows what I mean. There is a path from + to - without going through the solenoid and 4th gear switch so they are insignificant to the circuit and the LED lights based on ONLY whether the brake switch is open or closed.
led3.jpg

Where you put the LED in the circuit isn't going to make a difference... as long as it's part of the circuit 'loop'. Any of the 3 spots below is fine.
led2.jpg
 
:eek:

o.k. here I go again, I'll move the LED and try it again tomorrow.

Really appreciate this help. Just a matter of time before I get it.:rolleyes:
 
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