Here are your parts
Model LE7080XTW1

the dryer seems to only have high heat no matter what setting i use. i have read a few similar posts and it sounds like the operating thermostat. does anyone know how it works?
Your thermostat is adjustable, you can adjust the shut off temperature between 135 and 155 degrees. When it hits the set temp it opens shutting off the heating coil. When it cools to about 30 degrees below the set temp it closes and starts the heating coil again


i would like to test the system to make sure. how do you test the operating thermostat and its system?
I usually just take a soldering gun and heat up the metal face while measuring it with a meter. If it opens the closes, then it is probably OK.
They usually do not fail by changing the set temp, failure is either they do not close at all (contacts blown) or they do not open (contacts welded together)

why do you electrically heat a thermostat when you have hot air blowing right by it?
On high heat the thermostat is just heated by the heat from the heating coil. When you want a lower temp the thermostat heater is turned on. Now the thermostat not only gets heat from the heating coil but also from the thermostat heater so it reaches it's set temp quicker and shuts off more often. This results in less on time for the main heating coil and results in a lower overall temp.
Note: often there is also a variable resistor in series with the thermostat heater, this regulates this heater and gives more control over the dryers temperature.

You should be able to check the thermostat heater with your meter.
I could not find a wiring diagram for this unit so am not sure what it should measure. I think between 5000 to 8000 ohms. Make sure to remove the wire from one side of it when measuring to ensure you do not measure an alternate/parallel circuit path.

Hope this helps.

i ran the dryer on its own and the exhaust temp was anywhere from 115 to 150. but it didnt change by adjusting the temp dial. the tstat was turning on and off automatically (checked with voltmeter).
The temp setting should make a difference. I would check the vent system, it may be impeding the air flow so the unit is not cooling down correctly. Perhaps run it with it disconnected from the vent system. See end of this post.

what voltage is sent to the tstat heater? 110 or 220? AC or DC?
Usually it is 120 AC, but I cannot be 100% sure of this as I do not have a wiring diagram. Check in your control console perhaps the wiring diagram will be there.

is it dutycycled or is the voltage reduced by the main timer switch?
Normally it is the temperature control switch, I believe a variable resistor.
Similar models show a thermostat heater of 7,000 ohms approximately and a temp selector variable from 10 to 10,000 ohms.

I just noticed that you have a board in the control console and a sensor (moisture) in the drum. Clean the sensor with isopropyl alcohol. The way the sensor works is that moisture from wet clothes make a circuit path between the two wires of the sensor this tell the unit the clothes are still wet. This holds the timer off.
This is a long shot as usually all it does is keep the unit running longer if dirty.

VENT TEST
Undo the dryer from the exhaust
Run a load
Check the exhaust temps at different settings, you should be able to tell the difference just with your hand.
Clean/check the vent system if it now gives different temps. Make sure the outside louvers open fully.

If you do not want lint in the house.
Take a pair of pantyhose, put one leg into the other and attach this to the dryer exhaust.
Leave enough room behind the dryer so it can blow out like a windsock.
Run a load.

Both the above will allow you to check the air flow and temperatures.