Mitsubishi City Multi

[chillermac]

Hey people,
Got a call today from a customer saying that one of his offices is not heating. This happened about a week ago. There are 9-off indoor units each with their own controllers. The system is about 15 years old. In cooling mode there is no issue at all.
This one unit will not heat. The particular indoor unit is number 7 of 9.

I am pretty new to this type of equipment, spent most of my life on chillers, so forgive the ignorance.
Is it possible that this is the indoor valve stuck?
Can the head of the valve be changed without removing the refrigerant?
I had a quick look at it today, but need to go back to site, log the system through M-net and get all the temps/pressure and valve readings, but hoping someone may have come across this before..

[The Viking]

Find the BC box and check the solenoid heads inside.
Most likely you will find the solenoid head for unit 7, heating, to be open circuit.