I have a Duo-Therm airconditioner Model # 52712C. The compressor kicks on and seems to be running, however neither fan is working. It doesn't seem both fan mtoors would burn out at once. Could it be the two capacitors or the control board?
Many of these units use one motor to turn both fans. That said, you could have a bad selector switch (off,fan,cool) that is not sending power to the fan, a loose wire, some foreign object jamming the fan blade, if the fan/cool selection is made at a wall thermostat, you may have a bad fan relay. Of course, it could also be a bad fan motor. The only way to know for sure is to check it out with a voltage/ohm meter. If you are not good at electrical things, find someone who is to do it for you (there should be a diagram inside the unit and/or in the manual). It would be well worth the few bucks you may have to spend to get someone honest.
Are you sure that it has two different fans? I have two of them and each has only two motors, one for the compressor and one for the blower. And they are also DuoTherm. I have never seen an air conditioner that had two seperate blowers.
If your ac has a heatpump capability it may be the control circuit as one of the modes during heatpump mode is to run the compressor only, without fan, to melt ice off the expansion coil. You have only one fan motor.