Mitsubishi Electric Split Help

[maxcool]

One of our sites has various Mitsi Elec split systems on. Mainly the older 407c systems.

We have had a fault come up recently that keep causing the system to go into fault. We are suffering with a U1 fault. I am sure this can be caused by a high pressure switch issue. Possibly being open circuit?

When guages are attached, the standing suction pressue is very high however we are unable to get running pressures due to the system going into fault instantly on start up.

Any help, advice and things to check would be much help

PUH-P4YGA -


We also suffer with another fault 5102 on a similar system. I believe this to be a sensor fault? Again, any help on this would be much appreciated.

Thanks in advance.

[Paul a/c]

Hi have you tryed looping out the hp switch, test for testing? I had a5102 fault on a r22 system had to replace the gas in the end il

[Thermatech]

In the Mr Slim R407c service manual U1 is for
a/ high pressure switch 63h

b/ Abnormal low compressor current or open phase power supply.
Most fixed speed compressor R407c Mr Slim outdoor units had a CT compressor current sensor on the V phase of the compressor. It will trip for low current after 0.7 second.
In this case as your unit stops instantly at start up this could be the cause.
Suggest check power supply & compressor contactor 52C. Check compressor windings.
At start the compressor should pull high lock rotor start amps on all three windings so with clamp meter you should be able to test this.
The CT sensor is on the control circuit board so the CT sensor or the circuit board could also be faulty.
BTW
the 1ph outdoor units also had a 49c compressor internal thermostat & if that is open circuit then the CT current sensor will trip.

All fault codes starting with 51 are for temperature sensor thermistor open or closed circuit.
5104, 5105 & 5107 are for the outdoor temp sensors on most R407c systems so suspect indoor pipe temp sensor for 5102 fault.
Sensor resistance should be about 6 Kohms at 20 deg C for all sensors except for the Th4 compressor discharge which will be 250 Kohms at 20 deg C

[Peter_1]

Thermatech, as usual of course, a very good post.
Thanks:cool: