I had no idea. My brake lights were constantly on and I troubleshot it down to this switch. I think I knocked it lose when I was checking the fuses initially. Is there a proper adjustment for this switch? I just pushed the switch back in until the lights went out when the brake pedal was not depressed. Should I adjust it further? Thanks so much for the info.
It should rest just behind the pedal. Maybe 1/16th - 1/8th of an inch. I don't know if there's an exact OEM measurement, but basically the switch should engage as soon as the brake pedal is depressed even just a hair.
I have an auto trans. How does this switch operate the torque converter lock-up solenoid? It seems like a simple switch to turn brake lights on or off. When cruising, the switch is depressed due to the brake not being used and the brake lights off. So could you explain how all this works? Thanks, Evolution 1980. Learning something new so please bear with me...
The switch also acts as a breaker to the 3v circuit that goes to and engages the lock up solenoid. (Also referred to as a Torque Converter Clutch ("TCC") solenoid.) When the 3v signal engages the TCC, the TC will 'lock' and spin at the same RPM of the engine, thus no longer using "torque multiplication". This is like having a manual tranmission of sorts, as the transmission is directly connected, or 'locked', to the engine. What would happen if this stays locked is the same thing that happens if you don't use the clutch when coming to a stop...the car would stall because the transmission would physically stop the engine's rotation. When you hit your brake, that switch behind the pedal breaks the 3v circuit thus releasing that "lock up".
It's not uncommon for the actual solenoid to go bad. Nothing 'bad' happens inside the transmission except that you don't get that 1:1 lock. Most people may not even know that their's isn't working until it happens to be noticed by someone diagnosing transmission problems or they just happen to notice that their RPM's in their highest gear are ever so slightly higher than they used to be.
Besides dropping the pan and checking the solenoid operation with a voltmeter, one easy way to check is to go out on the highway. Do about 60mph or so, as long as you are in your top gear.
Ever so gently apply the brake. It should only be enough to trigger the switch/brakelights, but not actually engage the brakes. You should notice your RPM's jump up a couple hundred RPM's. You won't likely
feel anything because the brakes aren't actually engaging, but you'll see it in your tach as the lock-up releases and the TC goes back to using toque multiplication.
When I was troubleshooting problems with my original TH350, that's when my mechanic noticed it wasn't working. So we installed a diagnostic light on my dash. If I have the 3v going to my solenoid, the light is on. When I lose that 3v, the light goes off. Thus, when I hit my brakes, that light goes off. Now I'll know for sure if that solenoid ever goes bad again. It's overkill, but it was primarily meant to be simply a troubleshooting light. I ended up just leaving it there.
If you are hungry for more info, you can always ask here or google it. You should be able to find a couple different references.
