Mini split ac reverse valve malfunction

[kefah]

Hi
most of ac unit here are heatpump
the RV only feeded in winter so in summer most are de enrgized
i got many call of no call in these very hot days
so i found that RV are stuck in middle or in heating mode
then i energize it manually to reset it to cooling mode
and its ok
i thought the rv may get to middle or to heating mode due to wrong feed from pcb or wrongfully setting remote controll to heating mode so i disconnect RV Wires from PCB

but in some 2 ton ac
and after 3 dasys of work the RV moved to middle or to heating mode

so i tried to feeded it manually but it stuck in heating
so i will replace it
my quesion y RV move to HEAT mode even if i disconnect it wires????

[The Viking]

OK,
It doesn't actually move to heating mode. It get stuck, either because of debris in the sliding mechanism or the capillary tubes controlling it being blocked. Another reason for them to stick is that the seals melted when the valve were brazed in to the system.

Next question is why...
If you got a clean system there is no debris inside to find its way in to the valve.
This is the type of faults that occurs when the installer didn't follow "best engineering practices".
Were nitrogen bled through the pipework when it was brazed?
Was the system properly pressure tested and evacuated?
Is there still moisture in the system?
If the valve been replaced, was it "wet ragged" whilst it was brazed in?

Simple fault to find, difficult fault to find the cause of.

:cool:

[kefah]

all unit i encountered were not has leak or serviced
all are standard
where
some unit were working since 7 years
some were 2 years