AC cycling - advice please.

[ss2115]

Last year we replaced the evaporator in our 1995 850 sedan.
Big job but no problems.
Had it evacuated and gassed up by a professional - no problems and it pushes out good cold air.

What it always seem to do though is the compressor cycles on/off every 5 seconds no matter what the outside temperature is. Even on hot days it still cycles in these 5 second short bursts.

I've had the gas pressures tested again and all is okay.

I've often suspected the pressure switch on the pipe about centre of the firewall is faulty. If I jumper it out, the AC stays on and doesn't cycle (at idle).

My question is, does the AC depend on this pressure switch to detect high or low pressure to control the cabin temperature, or does the AC unit inside the car have a thermister or some type of temp control?

In other words, I don't wish to jumper the pressure switch and go for a test drive to see if the compressor cycles at longer intervals if this switch is the cycling control and the AC explodes by being forced on continuously.
Or can I prove if this pressure switch is just a failsafe and behaving faulty in causing the constant cycling?

At idle, if I jumper this pressure switch, the AC stays on and the evaporator pipe coming through the firewall ices up which I haven't seen before.
But I don't want to go for a drive in case I'm wrong about the switch and i cause some serious damage.