R134a Fosters Fridge - Scratching my head!!

[Brew]

Currently working on a Foster Fridge FPS5HR, a 5 door prep Fridge in a Restaurant. Initial inspection showed Evap at room Temp (25C), Condenser/Evap was reasonably clean, All fans operating, System calling for cooling, Comp Running. Chucked a Gauge on the Comp Head, 0psi, Threw two line taps on where I could, one on the Condenser Discharge showing around 90psi. One on the Comp Suction showing 0psi.

Initial thoughts were low on Gas, So I weighed out 760grams (supposed to have 800g, guess some stuck in oil), Chuck 800grams of fresh R134a in. Still no Joy. Chucked in another 100grams, just for good measure, no joy.

Still the same, all valves equalise on Gauges when the system is off, showing there isnt necessarily a blockage in the capillary. When I power up, the Condenser discharge goes up to 90psi. Comp Head matches the suction into pulling a Vac, which I presume goes all the way back to the evap coil.

So I was convinced this must be something to do with the capillary, perhaps some moisture build up that it cant shake, and it only lets a small amount through, I reclaimed the gas, Chucked Nitro through it several times, Triple Vac'd, regased, still no joy.

So today I returned to the job, I decided to replace the capillary, perhaps a bad call, but I cant see how this can necessarily be a compressor fault as its pulling a vac on the suction and evap discharge does increase when the comp kicks in on startup. So I replaced the capillary, taking care to keep the line on the top of the pipework and away from any potential oil buildup in the system. Threw on a filter drier. put it together. [edit] I did a pressure test in through the condensor discharge and the resulting nitro came out through the Comp Suction, suggesting I didnt block the capillary by accident. Vac'd for an hour, Regased, and still no joy, system is still at air temperature. Suction pulling a vac and 90PSI on the Condenser discharge.

I can see some slight frosting initially buildup just before the capillary the evap inlet is still ambient.

Hopefully im not being a nonse here but im not a complete expert in the trade still much to learn! But all I can consider now is that the compressor is not providing enough PUSH on the discharge to get the gas through the system. So essentially a Compressor change.

Any thoughts?

Thanks in advance