Here are your parts
Parts for Frigidaire FDE336RES2 Dryer - AppliancePartsPros.com

Here is a copy of the wiring diagram.
http://manuals.frigidaire.com/p...df/Webster/131850300.pdf

Attach one meter lead to L1 prong on he line cord and leave it there.
Use the meter's most sensitive resistance scale, also short the meter leads together before starting so you can see if there is a zero offset in the meter.
Set the unit to mid-scale of a heated timed dry cycle.
Now work your way through the heater circuit to find the fault.

Red wire at the terminal strip (L1) should be 0 ohms.
Connections B and A at the timer should be 0 ohms.
Both sides of the control thermostat (orange wires) should be 0 ohms.
Both sides of the high limit thermostat should be 0 ohms.
One side of the heater (black wire) should be 0 ohms.
The other side of the heater (yellow wire) should be about 12 ohms.
M1 at the motor should also be 12 ohms.
If all the above are OK then odds are that there is either a problem with the heater's centrifugal switch on the motor not closing or the wiring from the switch to L2.

I do not know if there is a problem with the wiring diagram but on most units L1 is black and L2 is red so the above may not be correct.