tmcc s crescent problem

I'm confused, what are the exact symptoms?  Are you saying it takes off at full speed whenever you apply track power?  Can you blow the whistle from the remote?  Does it reverse from the remote?  Is the Boost button stuck on the remote?  Are you using a CAB1 or Legacy CAB2?

THANKS FOR REPLY THE LOCO ACTS AS IF THE BUTTONS STUCK ON CAB 1 SO I TRYED RUNNING CONVENTIONAL AND ITS STUCK IN BOOST MODE. DONT THINK ITS THE CAB 1.

EVERYTHING ELSE ON THE REMOTE WORKS HORN ,BELL AM USING CAB 1 THANKS JOHN, JEFF.

So, without the command base powered, it will only run in one direction?  There is no "boost mode" in command, so I'm looking for the symptoms you see.

In command mode, can you reverse the direction of travel?

YES I CAN REVERSE ON THE CAB 1 REMOTE,AS SOON AS I TURN THE RED THROTTLE BUTTON IT TAKES OFF IN FULL SPEED,IT SEEMS STUCK IN BOOST MODE EVER SINCE I PUSHED BOOST.

OK, I don't think this is a TMCC issue at all.  Top suspect is the encoder on the motor, my guess is this one has Odyssey speed control, and the magnetic ring has cracked or shattered and you have no speed control.  The symptoms are as soon as you touch the throttle in either direction, it takes off at full speed.

If it has a switch for the speed control on the engine, try turning it off?  It would help us a bunch to have the exact Lionel model number for the locomotive.

THANKS JOHN AGAIN! S CRESCENT 6-38064 ,I TURNED(SWITCH UNDERNEATH) OFF ODYSSEY AND I HAVE CONTROL ,ITS NOT TAKING OFF.

Well, that's an Odyssey failure, and by far the most common failure of that system is that magnetic ring on the motor.  To go further, the shell will have to come off to check on the health of the motor encoder.

One other thing that occasionally happens is loose connectors, though I find that a lot less than the broken ring.  The gray magnetic ring should be firmly attached to the brass flywheel, if it's loose it won't work.  It could also have broken, then you'll find the pieces inside the engine.