I was called to look at no heat coming from Rads. Initially there was an E5 fault so I checked the comp/inverter board to conclude the comp needs replacing.
I then coded out the faulty comp to run the left hand comp.
Here's the question I'm looking for help with

The left hand comp run and hot gas can be felt going down the pipework to the indoor unit and chilled air coming off both external coils. After a couple of mins a valve can be heard opening/closing and a rush of hot gas being directed into the left hand coil. So now we have warm air coming off the left hand coil and chilled air coming off the right. The hot gas going to the indoors down the pipe work becomes just warmish.
Any one got any ideas why hot gas is being diverted to the left hand coil?