Oil Pressure Problem

Help!  I have recommissioned a 1983 1.8 Injection GLI Cabriolet after standing for 3 years and I am wrestling with an intermittent oil pressure alarm.  This comes on at about 3200 RPM (not 2000) until the car has been running for a while.  After that it seems to be OK irrespective of revs.

I have checked:
1. The oil pressure with a gauge - fine.
2. Both oil pressure switches - operating correctly.
3. Voltage on wires to oil pressure switches - 12V present on each when ignition switched on, nil when ignition off.

I have inspected the back of the instrument cluster and flexible 'printed circuit' wrapped around the back.  All the conductor tracks seem OK.  The Haynes wiring diagram refers to a specific oil pressure relay J-118 but I can't find this.  All the instrument functions work except the 'Change Up' light (and the oil pressure alarm!).  To fix other electrical problems I have renewed the relay/fuse board.

I have seen reference elsewhere to 'an L-shaped printed circuit (PCB). Is this the blue plastic sheet with copper tracks?  Is this where the alarm logic lives and are they available anywhere?

Any ideas?

the oil relay mentioned in the haynes is the same as the 'L shaped' pcb mentioned. if you pop the speedo out of the cluster you'll find the oil warnign pcb is clipped to the inside of it. its easy to swap this for another

Are there any trick to removing the speedo on its own?  Also, how would I source a replacement PCB?

Thanks for your help so far.

once you undo the 8 screws on the back its pretty simple the whole lot flips open and then its a screw for the voltage stabilier and maybe a plug for the mfa loom if it has one. for a replacmeent tyou would need another set of clocks i think as i dubt gettign a new pcb would be easy. im sure there are a few peeps on here with damaged clocks who could donate one?

Thanks- I was trying to get the speedo out without removing the rest.  I see the PCB.  Any offers of a spare speedo would be gratefully received.