Aircon - pressure in low pressure pipe 'too high'

[d27426]

Hey, our aircon has been intermittent the past few years.
- I'm a dab hand at changing the relay now.
- The fuse is good.
- When I turn the air-con on, the fans get really noisy.

But no cold air.

I bought a R134a refrigerant and a filling and pressure gauge at Halfords over the weekend. When I attach it, it says the pressure is off the scale to the high end and is 'WARNING'. ( The gauge seems to work fine on another car. )

Any suggestions what might be causing this please?

[d27426]

Looking at this https://clubjazz.org/forum/index.php?topic=12285.msg85527#msg85527 then it might be that the compressor is not actually kicking in. I wonder if I've been stupid and put an old relay in y mistake.