Why does the pump run only when the switch is held depressed?

SOURCE: Drum doesn't turn, start switch

Make sure there's power getting to the dryer. Check for a tripped circuit breaker or a blown fuse. Check the wall socket for power with a voltmeter or by plugging something else in.
2. Door switch / Door switch actuator lever
The 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.

3. Thermal fuse
Most dryers have a thermal fuse, which burns out when the dryer overheats, in which case the dryer will either not run at all or stop heating. The fuse is usually located on the vent duct, inside the dryer. A blown fuse will show no continuity when measured with a meter. Before replacing the fuse, make sure the blower wheel is not broken or clogged, and there is nothing blocking the venting.

Note: It is recommended by most dryer manufacturers to replace a hi-limit thermostat when replacing a thermal fuse.

4. Timer
Replace if defective (note: uncommon problem).

SOURCE: Ingersol T30 won't shut off and blows pressure release valve

the wire juction box on your compressor has a pressure switch that may be wound in to tight take the cover off the box there should be a switch with a machine screw with nut and washer and spring back this nut off and see if that helps if you go to far you just crank it back in until the switch hit although it may be the other way around you may have to tighten to lower the pressure some of them are made that way if this does not solve your problem send me a picture of the switch and can solve it from there

SOURCE: Kenmore Elite 63942 dryer goes on with a push of

could have a bad even heat board,send model number so i can look it up

SOURCE: Garbage dispoal air switch not working

make sure the airline is secure, a slight air leak could cause this problem

Testimonial: "Thank you."

SOURCE: Clothes Dryer won't stay on after switch is depressed.

some of them dryers have a switch other than the push button located behind the console. it also has an identical heat switch beside it. if that holding switch is bad it will not stay running. of the two identical switches the run switch is on the left. good kuck.