What is this switch called?

[Daveo91Burb]

The one on the bottom of the pic is the regular brake switch. Normally open, triggers the brake lights and cruise cancel when closed, i.e. when pedal is pushed. This is what comes up when you search for a "brake light switch" on RockAuto or a parts store. The one on the top of the pic, though, is normally closed and when opened, it tells the computer that the brakes have been applied. The guts of this switch on mine are gone and the two wires (pink - ignition hot lead; and purple - goes to terminal on computer) are jumpered together. So the PCM thinks the brakes are never applied. It doesn't seem to cause any problems this way, but I think it affects how the torque converter lockup is disengaged. I just want it to work as designed so I need to replace the switch, but I don't know where to get it or even what it's called. Anyone know what that switch is called?

You must be registered for see images attach

 

[Blue Ox]

I always thought the upper one was the cruise disengage. I'll look in the a.m., but I'm pretty sure my pickup has one and it has a THM400.

 

[yevgenievich]

I had to find it before. Need to look back at some notes. Also used a combination switch from a 4th gen fbody before.

You must be registered for see images attach

 

[Vbb199]

It disengages lockup for the torque converter i do believe.


What @Blue Ox was maybe referring to in his pickup is the kickdown for the th400 (i think) Or i guess specifically, for passing gear

 

[PrairieDrifter]

It disengages lockup for the torque converter i do believe.


What @Blue Ox was maybe referring to in his pickup is the kickdown for the th400 (i think) Or i guess specifically, for passing gear

Correct. Torque converter switch. Unlocks the converter at lockup speeds, when the brakes are applied.

 

[AKguy]

So, when did they start using the locking converters? Would the 1985 Suburban with the 700R4 be equipped?

 

[PrairieDrifter]

So, when did they start using the locking converters? Would the 1985 Suburban with the 700R4 be equipped?

Whenever the 700r4 began I'm pretty sure. Thats how it achieves overdrive. My 84 has it.

 

[AKguy]

Thanks!

 

[Blue Ox]

The kickdown switch for a 400 is on the throttle. Mine has a second switch on the brake pedal, but it looks different than yours. I still think mine has to do with the cruise, but I'm not going to chase it right now. Yours probably is for the converter as these people have stated.

You must be registered for see images attach

 

[Vbb199]

So, when did they start using the locking converters? Would the 1985 Suburban with the 700R4 be equipped?

1982 for the 700r4

The th350c also features a lockup converter in a desperate attempt to get better mpgs

 

[Daveo91Burb]

Thanks for all the input. I solved my problem. I actually had a regular, combo brake light/CC switch that I bought a few years ago before I realized there were two switches down there and it was the other one that was bad. I installed that extra switch in the location of the TCC/PCM switch and used the cruise socket to plug in my connector to the PCM (computer). I had to use the barrel of the old switch as a sleeve since of course they're different diameters. Works great, I have the ability to datalog through the ALDL port and the PCM now definitely sees when I push the brake pedal.

I'm glad I was able to adapt the other switch. I still am not able to find a TCC switch, ABS brake switch or anything other than the regular brake light switch (with or without cruise).

 

[gmbellew]

I am going to have to crawl under my dash. my brakes don't unlock the tcc on my 90 burb. I realized this, because I had a bad IAC and the computer was having troubles knowing when I let off the throttle and would keep the tcc engaged until the transmission downshift (either from acceleration or deceleration). once I replaced the IAC, it started unlocking again as soon as I let off the gas but if I keep the gas down and tap the brakes, it doesn't unlock. the redundancy in the system has it functioning properly, but I need to check the adjustment of the second switch and maybe replace it. good info in this thread.