Here are your parts
Replacement parts for Roper REX4634KQ1 DRYER | AppliancePartsPros.comSee the attachment for the tech sheet.
The way it works is that:
In timed dry the timer motor gets power directly from the line (240 volts)
In Auto mode the timer gets power through the heating element when the element is shut off by the thermostat.
First I would unplug the unit and set it to auto mid cycle.
Then measures Timer switch 0 contacts TM to OR, they should be 0 ohms.
If OK
Check the heating coil.
Unplug the unit and both wires to the coil.
Check it with a meter, should be around 8 to 12 ohms.
Then check from each side of the coil to the case/frame, both should be infinite ohms (open). If not the coil may have sagged or broken and is touching the case. This can cause it to run all the time and the thermostats cannot regulate.
If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.
4. When you start always short the meter leads together. This will tell you that the meter is working and if there is any 0 offset.
There is a good STICKY at the start of this forum about it's use.