Have to pull the start/timer knob many times to get the dryer to turn on. Have replaced timer and door switch.

If you are setting the knob to begin a cycle AND the drum turns when you start it AND the timer knob does not advance, the timer is likely defective.

Some dryers with truly automatic cycles (using moisture or temperature sensors) will not advance the timer if there is a no-heat condition due to a bad thermostat or heating element. This would show as the dryer tumbling a load forever and the clothes are cold and wet when checked.

If the dryer will not do anything at all AND the timer knob does not advance, check the power (circuit breaker/fuse), then the dryer door switch. When the door switch is defective or the door isn't fully closing, it stops everything, period. There is a thermal fuse on some machines that will also cause this problem.
Good luck from Detroit, MI.

Disconnect power to the dryer and remove the screws attaching the console rear panel to the console and pull the panel off.

Inspect the wires connected to the timer and ensure a snug fit connection. Clean the connectors and terminals then reseat it several times to ward off dirt within the connectors.

Reconnect power to the dryer and start it; replace the timer (part number 3398195 ) if the dryer still won't stay running. Unplug the dryer and pull the timer knob off the console. Remove the screws securing the timer to the bracket and remove it. Secure the new timer in place then disconnect the wires from the old timer one at a time and connect it to the corresponding terminal on the new timer.

Push the timer back into position on the console and secure the console rear panel in place.

whirlpool electric dryer will not start when you push start button. Model No. LER5634AW0. There is power to the dryer. The door switch appears to be working,(didn't check it with a meter). I push the start button, run it through all the cycles and still nothing. Are there any resets or circuit breakers that I could check? Where do I go from here?

i dont there is a pull out knob on dryer there should be a start button knob is to set time make sure door is closed and push all buttons ans see what happens

sounds like the door switch isnt fworking

If you push the knob to the left and it makes a good contact and starts the machine, then replace the timer switch. Write down the Name and Model Number of the machine (usually on or below the door)
take it to a local appliance shop and order a new part. When you recieve the new part UNPLUG the machine and remove the three screws from of the top of the electrical compartment and gently pull o the front open, there is only one plug attached to the switch, remove it and dislodge the old switch, then snap the new switch in place and replace the plug, close the compartment and replace the three screws, plug in the dryer, and try it.

IF THIS MODEL USES THE TIMER TO START THE MACHINE BY PULLING OUT ON THE KNOB, I HAVE HAD TO REPLACE QUITE A FEW TIMERS FOR THIS PROBLEM. SOMETIMES BY MOVING THE KNOB UP AND DOWN AND SIDE TO SIDE WHILE PULLING WILL START THE MACHINE. IF SO, REPLACE TIMER.

 Door switch / Door switch actuator leverThe dryer would not start with a broken door switch. Replace the door switch if found defective.

Most dryers have a door switch actuator lever - when you close a dryer door, it presses against the lever, which actuates the door switch. If the lever is broken, the switch would not activate and the dryer would not start. Replace the lever, if broken.

Note: Door switch actuator lever usually comes with the door switch assembly and it is recommended to get the whole assembly since there is almost no price difference between the door switch assembly and just the lever. Check your model for more details.

when you turn the select knob, you set up the internal cams of the timer. when you press to start or pull to start, you energize the timer motor (buzz) the timer opens the water solenoids. the diaphragm switch senses the water level and moves the timer to the next step. agitate starts for the timed cycle. when its finished the motor kicks in in opposite direction to drain and pump water out.

If it intermittently starts when pulling the start knob a few times then it is strictly the timer start switch. I believe this is an electronic timer as opposed to the mechanical ones but it can only be bought as an assembly. Check also your door switch if it is intermittent. I will also not start if door switch is deffective. If in doubt replace them both if they are inexpensive. Make sure all POWER IS OFF when you're diagnosing it.