Mitsubishi 1302

[Jack c]

Hi, has anyone had a 1302 high pressure fault, when in cooling mode only, on a Mitsubishi electric city multi PURY-P250YMF-C (R407c).
I have a refrigerant flow problem which is making the system run in high pressure on both sets of service ports at 100psi suction with an increasing head pressure from 225-400+ psi over a two minute period before cutting out on hp fault.
With guidance from Mitsubishi we have checked BC control box and removed LEV1 and checked gas pressures when valve is fully open as well as checking temperature diff on probes using sw1 switches.
I suspect that the condenser unit solenoid valves or check valve are faulty, as the condenser coil is not warming up with or without the condenser fan motor running and the discharge pipe to the BC box is abnormally hot?

[james10]

i had the same problem a tech from a different company had faulted a check valve on the system and installed a new one, the wrong way round and made a right mess of the job. if memory serves me right it was check valve 7.in the end i condemed the system as to replace this valve after he'd butchered it i would have had to heat a 10kg block of brass on the header to change the pipework quite difficult giving it's position inside the unit

[Thermatech]

This one can be a trial to be sure of exact cause but you need to follow the hot gas through the outdoor unit very carefully.
After the discharge check valve the 1st suspect is the 4WRV. If its jammed in heat mode then all hot gas will be going to BC box.
If in cool only mode & no hot gas in outdoor coil then problem could be solenoid valves for the 4 sections of outdoor coil or a bypass caused by any of the non return check valves allowing refrigerant through when should be closed.
Its not easy with the check valves as most are in a brass manifold block.

Tips
1/ Use 2 gauge manifolds.
one set on true HP & LP service ports & one set on service valves.
2/ Run system with all units in test heat & then test cool & carefully follow the hot gas.
3/ Try closing the liquid HP service valve for system pump down & see if in this extreem condition hot gas bypass in some place when it should not.


You need service manual & fully understand the correct refrigerant flow path for cooling & heating modes.

Good luck.

[Jack c]

Thank james10 for your reply that sounded like a real bodge job, thankfully I am pretty shore the check valve has not been replaced.
The unit was maintained only last month and was working with no fault that I know.

[Jack c]

Hi Thermatech thank you for all the information and tips this will be a great help, I am going back to the system next Wednesday to carry out more investigation works will keep you posted on my finding.

[Jack c]

Hi james10 and thermatech I have now been back to site and found unit with a faulty four way valve.
I am waiting for parts before returning to site, thank you for all the replies and helpful information I will let you know how I get on.