How Does a Heating Pad Switch Control Temperature Without Changing Voltage or Current?

Hi, let me start by saying that I do not have any formal degree in electronics, but I love taking thigs apart in order to understanding how things work. Presently I took my heating pad apart to understand how it works. I have been having a hard time understanding how the switch mechanism works. The pad has a button that enables the user to turn the pad: OFF->WARM(green LED)->LOW(yellow LED)->MED(orange LED)->HI(red LED)->OFF . . .
Regardless of the Warm/Low/Med/Hi setting the output Voltage and Current never changes but the pad temperature still changes per the setting. How is that possible?

Hi Barry,I suspect that the magic resides in the IC in the center of the board. I couldn't make out any markings in the pictures though.From your description, I believe that the IC is doing a pulse width modulation (PWM) on the output. This is supported by the presence of transistor T1 at the bottom left near the OUT2 wire.This Wikipedia article about PWM explains what it is.
https://en.wikipedia.org/wiki/Pulse-width_modulation
And this tutorial explains how it's done on an Arduino.
https://www.arduino.cc/en/Tutorial/PWMIt's likely that the IC in your heating pad is a micro-controller similar to what is used in an Arduino.

You don't say what current/voltage you are measuring and where, nor what your heating pad is powered from. Given that the PCB says ACL and ACN it seems that you are using mains power.  My guess would be that T1 is in fact a triac/SCR/thyristor and the temperature control is achieved by controlling the phase of the AC waveform out the heating pad.See this Wiki article