AX3500 controlling a power wheel

We converted a kids cadillac escalade into a mobile robot.
We are using an AX3500 motor 1 output to control a linear actuator to a belcrank for steering and the motor 2 control to activate the rear wheels.
It works great inside
We are using a R/C radio to control the bot for testing.
The problem we are having is outside. If we attempt any incline the motors chatter.
We bypassed the AX3500 and wire the little motors directly it will climb any hill .
We have tried to adjust the output to the controller.
Does anyone have any advice??

Obviously, the controller has no way of making the difference whether it is on a flat or inclined surface.
<P style="MARGIN: 0px">There may be something going on with the radio or antenna not receiving as well depending on inclinaison
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<P style="MARGIN: 0px">Another possibility is the motor drawing more current when going uphill and reaching the current limit. It should not make any noise but at least there would be a logical link. Try holding back the bot as it moves on a flat surface to check this explanation.
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<P style="MARGIN: 0px">Thanks for he quick response
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<P style="MARGIN: 0px">We measured 11.7 volts at the motor no load
<P style="MARGIN: 0px">We held back the bot and the voltage dropped to 1.8 volts when the motors chattered.
<P style="MARGIN: 0px">How would we check the current limit on the output of the AX3500?

It sounds like you don't have enough power to supply the motors. Make sure your batteries can supply the current your motors need. Also, are your motors rated for the power you need? (i.e. torque output?)

<P style="MARGIN: 0px">OK here is the final chapter on why the motors were chattering.
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<P style="MARGIN: 0px">The stock powerwheel battery supplied 12 volts at 9 amphour. So we supplied that to the AX3500. That was enough to run the powerwheel in the hall under little load. When you tried to go up a hill or load the unit the motors just chattered. When we hardwired the battery to the motors it worked fine because the motors did not care if it was 12volts or 11.6 volts. However, the AX3500 sensed an "undervoltage" and turned on and off thus pulsing the motors. We used an APC power supply of 4 batteries at 12 volts each and 7.2 amphour supplying 24volts to the controller and bingo the AX3500 has plenty of power and we are in big business.
<P style="MARGIN: 0px">I would like to thank everyone who weighed in on this problem.
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<P style="MARGIN: 0px">Another solution to this problem is to use a smaller separate 12V battery to power the controller's logic via the Power Control input, while the main 12V batteries power the MOSFETs via the Vbat input.
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<P style="MARGIN: 0px">In this case, the controller always gets a stable and safe 12V to power the MCU and mosfet drivers, even as the main battery voltage drops because of the motor load.