How do i change my LG sensor microwave oven to digital time

Push clock button and press the Up/down buttons to change time to pm.

F4 means sensor open, You have to check the Humidity sensor.
If you wish to get some details; visit the site linked here. Pull up older posts. http://electro-medical.blogspot.com/

EVER HEARD OF GOOGLE????

LG LMVM1935 manual
Google

That gets you to the manual.
Page 3 is the table of contents that lists oven light replacement on page 29.
Just maybe, if I teach you this you'll be able to do it yourself next time!

Ithnk you must check yo switches if there are still working fine but ithnk it may be the pc board faulty

Press Stop/Clear

Press Clock

Enter time e.g. 1015

Press Start/ Enter

Change Bridge Rectifier Diode And Capacitor Without Test by Meter,Some Time it will licks,Check All Connected Parts,And Last Is Transformer

With Power on Microwave There is Light Blinking It Means Is Normal Power Supply Supply Problem,Not Reaching Front Panel Power Supply

A hard reset, that is, removing the unit from the electric source and restarting it after a few seconds, solved the problem.

You are right. f4 means shorted oven temperature sensor (RTD). Check sensor harness and harness connection between oven sensor and oven control. Replace oven temperature sensor (RTD) if wiring is ok.