seschenburg

Attached are my references. Scanned from the 1994 service manual. Sorry they're all sideways, but that's how they scanned.

If there's something else you'd like to see let me know and I'll see if I can get it uploaded.

Though I don't see how a light bulb change would cause a problem here, LED's draw less current which could change the strength of the signals passed to the PCM which could certainly confuse any logic circuits. You can either add a load resister to bring things back to normal, or stick with regular bulbs.

VickMacky

If brake lights would unlock it wouldn't the blinker do the same thing?

seschenburg

Until someone can provide proof such as a diagram of the circuitry that shows a direct correlation between the lighting circuits and the torque converter clutch engagement circuit I still say this is an urban myth.

Just call me Sean

iTrader: (1)

Blinkers work independently of the brake lights, so no.
In your other post you just said the brake light switch sends a signal to the pcm to unlock the torque converter. So since the brake light switch unlocks it and the hazards run through the brake lights which run through the switch then the pcm would get an intermittent unlock signal, it would lock on its own but then think you were stepping on the brake and unlock. Then it would think you released the brake and lock, then it would think you stepped on the brake and unlock etc. etc. etc.

seschenburg

Actually I said that "...The PCM may then use this signal in determining whether to release the torque converter clutch, or not."

My point is that the engagement/disengagement of the TC clutch is controlled by the PCM, not by the brake/hazard/turn light circuits themselves which have no connectivity to the TC clutch circuits.

If you look at the page 30-1 file you see on the left that..."The BOO switch sends a signal to the PCM to disengage the torque convertor clutch when the brake pedal is depressed. This signal may be ignored by the PCM if TP signal is above closed throttle."

And, you'll notice that the lighting circuits are fed out before the BOO switch so as long as you keep your foot off the brake the BOO switch will remain open and there will be no braking signal sent to the PCM.

Just call me Sean

iTrader: (1)

The brake switch and turn signal/hazard switch are part of the lighting circuit. Unless the brake switch has two contacts it's getting a signal to the pcm to unlock.

seschenburg

I've provided documentation that satisfies my belief that this myth is BUSTED as far as it applies to a 1994 F150.

I'm not saying that you all don't know what you're talking about, I'm sure you do, but someone will need to provide documentation (a Ford TSB, service manual diagrams, etc.) supporting the myth before it can be called CONFIRMED in any configuration. Until then it's all just speculation and hearsay.

Just call me Sean

iTrader: (1)

Your documentation proves my point. The hazards give the computer an intermittent brake signal through the brake switch, which locks and unlocks the torque converter. You don't have to believe it, but it's right there in front of your face. I think you don't understand fully how electricity works.

seschenburg

You're funny.

I see a more in-depth explanation of this is in order.

So, first, the Powertrain Control Module (PCM) is the sole controller of the Torque Converter Clutch (TCC) based on signals it receives from sensors and through the Brake On/Off (BOO) switch. Any arguments there? No? Ok.

Second, as I've stated, there is no direct connection from the lighting circuits to the TCC. Power for the signal lights comes from the fuse panel through the flasher modules, through the Multi-Function (MF) switch, and/or through the BOO switch, through the indicator bulb(s), then to ground. You can see this in the 30-1, 90-1, 90-3, and 90-4 diagrams. As far as I can tell, there is no tap off for the TCC in any of these circuits. Please correct me if I am wrong.

Third, when the Hazard Lights are enabled you'll notice that the Hazard Switch, which is part of the MF switch, disconnects wire 511/LG preventing feedback into the PCM from the lighting circuits altogether. So, unless a fluctuation is being created in the power source or ground circuit there is no way for the hazard lights to modify the operation of the PCM which is the one true controller of the TCC.

Fourth, even with the BOO closed any voltage fluctuations caused by the Hazard Flasher (through wire 10/LG/R) should be easily compensated for by the power supply source resulting in a suitable voltage into the PCM pin 2 for it's logic to operate properly. But, again, I have no details on the operation of the PCM so, if someone else does, please share.

I have nothing else to add to this and, for me, the case is closed unless someone can provide an alternative explanation of how this all works.

Thanks to all, and have a nice day.

Just call me Sean

iTrader: (1)

As I said, you don't seem to understand how electricity works. But that's okay.