Ben1 wrote:There are normally 2 oil pressure switches, one is for the light and the other is for the buzzer
Not quite. The one between the pushrod tubes is used at all times, but the one behind the water pump (I'm thinking WBX here) is only factored in above 2000rpm. Both feed into the oil pressure light control system which lives behind the dash.
Before spending too much time on it, figure out the wiring & control system are all playing correctly. On my '88 2.1, the wiring comes into the engine bay at a two-pin connector forward/left of the engine bay, near the main fuse/relay box in there. One pin does the low-rev sensor, which says "PROBLEM!" if it earths. So leave that one disconnected for the moment. The other pin does the high-rev sensor, which says "PROBLEM!" if it _isn't_ earthed. So, for the moment, earth that one.
You should now have a reliably off oil pressure light. It should do nothing.
Now wire the low-rev wire to the low-rev sensor. You should now have the light coming on before you start the engine, going off almost immediately.
Now just disconnect the high-rev sensor wire. Make sure it can't earth. You should have the light off below 2k rpm, but cries of impending doom coming on immediately and all the time above that speed.
Finally, connect that wire to the high-rev sensor. You should now have a fully working oil pressure light.
If you haven't already replaced the sensors themselves, do so first.