Robot light turns red or yellow

We have lift mechanism that lifts the mobile goal when one of the joystick button is pressed (two 393 motors are attached to lift) and then it drops to the ground when the down button is pressed. After couple of up/down sequence, the robot light becomes yellow and also sometimes fully red.

port 2 = left wheel motor,
port 3 = left lift motor,
port 8 = right left motor,
port 9 = right wheel motor

We chekeced:

  • all wire connections are okay and secured
  • battery is charged.

What could be going wrong?

After Robot light is red then controller stops responding to any of the joystick button interactions.

This is the code snippet of lift task:

void setLift(int power) {
  motor[liftRightMotor] = power;
  motor[liftLeftMotor] = -power;

task lift {
 while(true) {
  if(vexRT[Btn5D] == 1) {
 } else if( vexRT[Btn5U] == 1) {
 } else {

In order to lift and move goal to any location; we have to keep pressing the lift up button and at the same time keep pressing drive forward button.

Should we connect the two lift motors to a Y connector and connect it to single controller motor port? Would that make it any better?

The “works a few times and then doesn’t” is pretty classic motor stall behavior. It’s possible that you’re very close to the max you can do with 2 motors running your lift (are they set for torque or speed? speed would make this problem worse). The motors are able to work really hard to move the MG, but in doing so, their internal circuit breaker (PTC) heats up excessively, and breaks the circuit/makes the motors stop.

So, I guess (1) make sure your motors are geared for torque (the gears that come installed on the motor from the factory) and (2) consider that you may be underpowered. Hope this helps.

it could be your joystick batteries going dead, or you have bad keys that connect your robot and controller

Your motors may be stalling, causing the battery voltage to drop.