Is this a GAS Dryer? Or, an ELECTRIC Dryer?
If this is an ELECTRIC dryer, and your dryer runs, but does NOT heat, you more than likely have a problem in the heating circuits. Any one of the following could be causing your problem:
1. Heating Element
2. Thermal Cut-Out (TCO)
3. Hi-Limit Thermostat
4. Improper input line voltage
5. Defective power cord.
The following link explains how to troubleshoot and diagnose a no heat problem on an electric dryer:http://www.fixya.com/support/r3576548-dryer_runs_but_does_not_heat
If this is a GAS dryer, the most common failure for heat related problems is a weak or blown igniter on the burner assembly.
It can take roughly 30 to 90 seconds from the time you start the dryer to the time it takes for the gas to ignite. If you are expriencing longer ignition times, the igniter probably needs to be replaced.
NOTE: This is a designed safety feature of the appliance that prevents free flowing gas from accumulating in your home without ignition. That's why you typically don't hear any gas flowing when you have an igniter problem. You might think you have a gas problem when actually you have an ignition problem.
You can purchase replacement parts (if required) at any of the following websites:
The first three sites on the list also offer some excellent exploded view diagrams of the appliance to assist you in locating and properly identifying the parts you may need.
If you have any questions, please post back with your complete MODEL NUMBER and let me know. I hope this can help you.
NOTE: Repairclinic.com has a repair manual that you can purchase that will help repair any Whirlpool manufactured gas or electric dryer (such as Roper). The part number is 1159257.