If it does not dry them all then the element is a good guess or the thermostat.
If it dries them but not all the way check that the moisture sensor is not turned down too far.
The following should help you.
How to Repair Heating Elements
A dryer sometimes won't heat or heats too slowly because of a variety of reasons. By following the guidelines below, you can inspect the heating elements on a gas or electric dryer to pinpoint the source of the problem. Troubleshooting the Gas Heater
In a gas dryer, heat is provided by a gas heater that is controlled by an air shutter. The gas heater is generally the source of no-heat or drying problems. You can often correct such problems by adjusting the air shutter on the gas burner, which is located along the bottom of the dryer.
To adjust the shutter, take out the screws and remove the panel that covers the gas flame. Turn on the dryer so the flame is burning. If the flame has a deep blue color and you hear air whistling around the burner, the air/gas mixture is receiving too much air. If the flame has a yellow tip, the mixture is not receiving enough air. Turn the thumbscrew or loosen the two screws slightly to increase or decrease the flow of air to the burner. Keep turning until the flame is a light blue color, without any yellow, and the whistling stops.
Gas dryers use an electric ignition device rather than a pilot light to light the gas heater: An element becomes hot and glows like the filament in a lightbulb. Electric ignition systems are always sealed; you can't adjust or repair them. If an electric ignition device fails, call a professional service person for replacement.
©2006 Publications International, Ltd.In a gas dryer, heat is provided by a gas heater, controlled by an air shutter.
Electric dryers have self-contained electric heating elements.
Servicing the Electric Heating Elements
Electric heating elements, found in electric dryers, are self-contained units located in the back of the dryer. A defective heating element is frequently the source of no-heat or drying problems. Remove the back service panel to gain access to the elements.
The heating elements are located inside the heater ducts. If you think a heating element is faulty, test it with a volt-ohm-milliammeter (VOM)
set to the RX1 scale. Disconnect the leads from the power terminals and clip one probe of the VOM to each terminal. The meter should read about 12 ohms. If the reading is higher than 20 ohms, the heater is faulty and should be replaced. Replace a faulty heater with a new one of the same type and electrical rating. A heater connected to a 115-volt line usually has an 8.4-ohm resistance; a heater connected to a 220-volt line usually has 11 ohms resistance.
The heater may also malfunction because it's grounded. To test for this, set the VOM to the RX1 scale and remove the leads to the heater. Clip one probe of the VOM to a heater terminal and touch the other probe to the heater housing. The meter needle should jump to a fairly high reading. If the needle flicks back and forth at a low reading, the heater is probably grounded and should be replaced. Here's how to replace the heater:Step 1:
Remove the back of the dryer. If necessary, also remove the cabinet top.Step 2:
Disconnect the leads and remove the screws that hold the duct in position. Then lift the entire heater unit out of the dryer.Step 3:
Remove the screws that hold the heating element in the duct.Step 4:
Slip the new heating element into the heating duct the same way the old one came out. Be careful not to damage the resistance coils. Replace the screws that hold the heating element in the duct, reconnect the leads, and screw the unit back into position. Servicing the Fan
The most common dryer fan problem is lint clogging the air passages through the heater and through the dryer drum. To clear a clogged air passage, remove the back service panel of the dryer and back out the screws holding the air duct in place. Then reach into the duct and remove all the lint and dirt possible. Reassemble the parts.
Also inspect the fan for a loose screw connection where the motor shaft is set on the dryer's drum. Remove the back service panel, tighten the screw, and replace the panel.