We need a instruction manual to know how to operation a Mitsubishi PUH-3VKA heating and cooling unit?

Could be a defective relay in the outside unit

Have you cleaned the indoor filters? It might be the system is low on refrigerant. You might need to call a qualified service tech to look at the unit.

the timer may have been activated at installation or by someone not fully conversant with the operation

use the remote and follow the instructions in the owners manual to turn the timer off

Check your filters, dog hair and lack of maintenance will definitely burden the cooling mode of the Mr Slim units.

hi.welcome to the mitsubishi worl of airconditioning.thay are great units to have.ok let me explane this for you.

the sun is for heat mode
the snow flake is for cooling mode
rain droplet is for dehumifiy the air if its a humid day.i hope this helps you.you have to choose the modes on the remote for the unit.then the unit will do the mode you choose on the day.

P8 error is abnormal pipe temperature indoor. If you are running it on heating P8 error will appear because the disc pressure is too high. It could be overcharged.

I Have same problem

The fact that nothing is coming on indicates that there is possibly a problem with your incomming power supply or wiring to and from the inside evaporator to the outside condenser. If all in good order, suggest you find someone you know who can operate a multimeter and check if there is voltage going to the control board inside the evaporator unit. If there is then almost certainly the control board would need replacement.

get model and serial #s and look up unit for diagnostic codes

Try to reset the error by disconnecting the circuit breaker for 10sec. and "on" again then operate the unit. But if wont work may there some parts that are defective that trigger the error E3. Replacement of pars is needed for this problem.