[PoorMansCat]

Have a 97 F350 2wd with 7.3L automatic....
Any time you turn on the blinkers the torque converter unlocks!.
It doesnt matter whether its left or right, you see the tach come up and feel it unlock the converter!. I replaced both brake light bulbs thinking maybe one of the turn signal filaments was broke and laying over on the brake light filament... and I disconnected the trailer brake controller, no help. The truck has a factory camper/towing package so it was factory wired with the 7way..
Looking for ideas on where to start with this... I thought about disabling the brake light switch and see if the problem goes away... but even if it does, Im not sure what that will tell me...
Any ideas, suggestions????

 

[Mark Kovalsky]

Is the bulb in the center brake light on the back of the cab good? A bad bulb there can cause this.

 

[PoorMansCat]

Wow, never thought to look there... I will check it and report back..
Does that bulb flash with the blinkers???

 

[Mark Kovalsky]

No, it doesn't flash with the blinkers, but it will affect the lockup if it's not working.

 

[PoorMansCat]

I have not been able to look at the truck yet... but talked to my b.i.l. and had him check it, sure enough, the light does NOT work. ITs currently at the muffler shop getting the r/s manifold gaskets replaced, when it gets back, I will replace the bulbs and try again...
Once again, thanks for all the help..

 

[isootmypants]

Also did the roof get stepped on or pressed down on lately? dome light will ground out.

 

[PoorMansCat]

Well, the roof hasn't been pushed down or anything....
Replaced the bulbs in the third light on back of cab... actually replaced both the clear bulbs as well...
THAT FIXED IT!!!..

Alright Mark.... care to do some 'splainin as to why it fixed it?.. does this have something to do with amp load on the circuit?

BTW... Thanks Mark for the help... would have never guessed that one..

 

[Mark Kovalsky]

I don't fully understand the circuit, maybe because I've never studied it. The PCM looks at the brake light circuit to determine when the brakes are on to unlock the converter. When a bulb is burned out something changes in the circuit and it causes the PCM to recognize the turn signals as the brake lights.

 

[PoorMansCat]

gotcha... I guess I could have put an amp clamp on the various circuits and maybe get a better understanding of whats going on...
One thing is for sure, I WILL keep an eye on that light in the future...
Once again, thanks a million for the help..