Heater doesn't work in Henmore air dry ( heavy duty 70 series)

It could be the clutch or the gearbox. It can be repaired, but top loaders are old dinosaurs these days. Front loaders are as big or bigger, and more efficient and cost a fraction of the cost to run in water and electricity for heating that water.

Series 70 is just that, a series. A model number will give you the cost of spares and how many have been discontinued?

https://www.google.com/search?q=Kenmore+Heavy+Duty+Series+70+parts

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Yours is a 2 speed motor. Does it spin in 2 different speeds. If so, then it most likely is designed with only to agitate in 1 speed. If it only spins in one speed, then your motor is defective

Yes, you need to take it all apart. ( Including the back.)
All of the things that can cause your problem are in the back and the bottom of your machine.
There are actually about 3 to 7 things that can cause "no heat".
Not only the "thermal fuse", but also the heating element, and any of the "overheat thermostat switches" can have failed, beside the possibility there is a wire has burned in two.
You will need a testing instrument like a multi-meter or a volt-ohm meter to check all these out.
Be blessed.

either the pressure switch is bad or the pressure switch hose from the wash tub to the pressure switch is kinked or plugged so air pressure cant reach switch and operate switch,remove hose at tub and blow into it and see if machine now operates,if not the switch is bad

probably your drain pump leaking it has a seal right where it attaches to motor,,,,mine is leaking there but haven't replaced it yet! lol

If you bought a new washer and you still have a leak, i guess it was not the washer but where it drains into. Sink or stand pipe has a leak. unless you are useing the old drain hose from your old washer. Dry up everything and look for the sorse of water with a bright light when the washer drains .

can you hear the motor or does the unit humm or vibrate when it is turned on
if yes then have a look at the belt
if not it's time sor a service call

sounds like you have a cloged vent i normally get a few calls in the winter timer for this problem because the vent is clogged outside due to the snow remove your vent try the dryer to see if it dries if yes check your vent

If it drains and won't spin you have to replace the direct drive coupling.

remove fill hoses and inspected for debris or cloggs ,,,,