We have a hoover 600mb top loader washing machine that will only operate in one direction on the wash cycle ?

Is usually a sign the washtub suspension is worn or broken.

https://hoover.com/support/manuals/?q=600mb

http://laundry.manualsonline.com/manuals/mfg/hoover/hoover_washer_product_list.html

https://www.washerhelp.co.uk/forums/topic/960-download-hoover-washing-machine-manuals

remove the bolt in the centre of the agitator, usually a 10mm socket and extensions to do it and pull out

Have a look for coins etc stuck in the drain pump or the tub outlet hoses especially where they fit onto the tub. If a coin or other foreign material blocks the water flow when draining , these machines wont spin properly.

If this machine has a motor that uses brushes, check them for damage, wear, or weak/distorted springs.

Check the lid switch for proper operation. If the switch is bad or not being actuated by the lowered lid, it will block operation of the machine.

I have the same problem. Just started missing the spin cycles and now I need to find which part to replace.
So far I think it could be: Aged contacts in the Timer, a faulty spin/no spin switch, or something to do with the brake/release mechanisms etc. ..I do know that the problem is electrical because everytime the motor starts the spin works fine; therefore eliminating in my opinion, the mechanical gearbox bits as a cause.

Try Replacing the drive belt.
Check it first to make sure that is functioning

timer or timer module fault

hi, i have a hoover 500 mb, occasionally it will not [ click into ] the wash cycle, then gets confused and does not spin dry properly