We bought a used washer & dryer. Our outlet is a 3 prong, the dryer is a 4 prong, so we got the 3 wire dryer replacement cord. Put it on and turned it on. After letting it run for 15 minutes, guess what, it does not heat up. I have checked it now after 20 minutes, still no heat, but one more thing, the timer dial is still on the same number that I originally set it for, which was 50 minutes. Please tell me what's going on and how to fix it. Thanks

When replacing the cord, how did you make the wiring connections?
What were the wiring connections of the 4 prong cord?

On a 3 prong, white goes to the neutral connector, black and red to either side. Remove ground strap from terminal block and connect to dryer frame .

The plug has nothing to do with it if you put in the jumper between ground and neutral as the book instructs (see below). These driers will not heat when the lint builds up like concrete on the inside of the air ducts. The thermal overload has blown open and keeps the heat from running. You will need a volt/ohm meter to find out which one has blown. These fuses are round with an oval flange that attaches it via screws to the sides of the ducts. When you are tracing the circuits they will wire the fuses in series with other safeties, so you can follow the wires to find all of the fuses and safeties. Also, the sensors get blocked from sensing when the dryer is dirty. Halfway cleaning it will not work because all it takes is one clogged up air passage or dirty sensor. You need to totally tear it down and scrape out and wash all of the parts except the motor, which you vacuum out. You can go to YouTube to see videos on how to take it apart, but do a very good job or it will fail again quickly. I would get a new belt and change it while you have it apart and get some white lithium grease and grease any bearings you find. You need to clean out a drier every two years, at least, according to the manual. You just unplug the wires from the sensors and remove ductwork that they are attached on and clean the entire thing with soap and water. Make sure you go all through the dryer and get all parts like the blower fan and housing (it has to be scrubbed and washed out), vacuum out motor well and clean exhaust. Mark all wires you unplug so you know where they go. If you leave any dirt in the ducts it will blow another fuse quickly or will not maintain the temperature correctly. This is an easier job than you would think. Make sure to clean around all of the sensors, if it has them. You can check them with a meter and the chart in one of the manuals, too. See: Dryer vent cleaning prevents fires - YouTube (http://www.youtube.com/watch?v=A6wmD502-xE) and: Cleaning out a dryer with top lint cleanout - YouTube (http://www.youtube.com/watch?v=OBNDbyRm68M&feature=fvsr)
Cleaning out a dryer: By a woman 2 of 2 - YouTube (http://www.youtube.com/watch?v=a73HTFkcB90&feature=relmfu)
Manuals: https://dl.dropboxusercontent.com/u/8010163/Whirlpool%20Dryers.zip