No Power to Transmission?

[djtejas]

We have the brake switch opened up. Cleaning up the contacts. Fixing he problem so now the question is. Why does the power from the brake switch give power to the front inside terminal on the transmission. I think it's "b" terminal. I thought the a terminal was the one with power all the time.

In the stock configuration it has 12v only when the vacuum switch is enabled at cruise, brake not engaged, and not in 4x4...it doesn't really have constant 12v, just when those parameters are met.
When people do their own version, many do bypass and wire constant 12v. But then the converter will still lockup in situations where you might not want it to...and then some people add a toggle switch to control it themselves...
Seems to me that the factory setup works best..

 

[dabomb6608]

Ok well thank you so much for your help.

 

[djtejas]

No problem...hope it works out

 

[Blue85]

There are two circuits...

The 1st is for 4th gear. The only times it should be unlocked in 4th gear are when you push the brake or when it is shifting down to 3rd (there in an internal switch to handle this).

The 2nd is for 3rd gear (even 2nd in some models...). This is where the vacuum switch is used. You only get lockup in 3rd gear when several conditions are met:
-High engine vacuum.
-Sufficient vehicle speed (hydraulic signal from governor)
-Low enough TV signal (from throttle valve)
-Brake not pressed
-Not shifting


Before the ECM lockup started, the third terminal on the transmission connector is actually an output. When all of the conditions above have been satisfied, there is hydraulic pressure to a switch, which provides a ground path. This is used for some emissions control things on the engine. I think EGR and evap purge.

 

[djtejas]

There are two circuits...

The 1st is for 4th gear. The only times it should be unlocked in 4th gear are when you push the brake or when it is shifting down to 3rd (there in an internal switch to handle this).

The 2nd is for 3rd gear (even 2nd in some models...). This is where the vacuum switch is used. You only get lockup in 3rd gear when several conditions are met:
-High engine vacuum.
-Sufficient vehicle speed (hydraulic signal from governor)
-Low enough TV signal (from throttle valve)
-Brake not pressed
-Not shifting


Before the ECM lockup started, the third terminal on the transmission connector is actually an output. When all of the conditions above have been satisfied, there is hydraulic pressure to a switch, which provides a ground path. This is used for some emissions control things on the engine. I think EGR and evap purge.

Yes, that 3rd wire is EGR...

 

[dabomb6608]

I dont have the EGR or the Evap Purge anymore. And yes i have noticed it does go into lockup in 3rd gear. Heck it will go into it around 30mph. It is really different hearing the exhaust change at certain speeds since i had been used to 2+ years of driving it daily without it working.
Today i had to bring it into the shop at school and clean up the contact points again on the brake switch. We put some dioelectric grease on it and made sure it still worked correctly, then put it back in and its worked great ever since.

 

[djtejas]

I dont have the EGR or the Evap Purge anymore. And yes i have noticed it does go into lockup in 3rd gear. Heck it will go into it around 30mph. It is really different hearing the exhaust change at certain speeds since i had been used to 2+ years of driving it daily without it working.
Today i had to bring it into the shop at school and clean up the contact points again on the brake switch. We put some dioelectric grease on it and made sure it still worked correctly, then put it back in and its worked great ever since.

On mine it was the yellow wire that went to egr...no egr now, so no yellow wire either..