I have an older spa I originally purchased from cal spas. It has a baker hydro spa pak model number 18B2504-1. its wired for 240 my question is the gfi is tripping....after opening the cover of the spapack I noticed there was rust on the pressure switch below the heater when I touched it it fell off could this be the cause of the tripping? and if so what test can I do to verify this?

Any help appreciated

great forum

possible but less likely - if your pressure switch is corroded and rusted like that, your heater is likely to be also,and its far more likely to be the cause of your gfci tripping
for the p/sw to cause this problem, water would have to have reached the electrical microswitch that you have in your fingers.
Apart from the heater - pumps, ozone and air blower can all cause tripping. you will need to narrow down the search by disconnecting and testing - i'd disconnect your heater as its most likely in this scenario