Oil pressure light problems

I recently installed a new omix instrument cluster and the fuel gage appeared to read backwards. Did some troubleshooting per omix instructions (and some folks here) and found that when I grounded the sending unit separately the gage pegged to full - I expect this is accurate as the tank is full.

Problem now is the oil pressure light comes on and stays on when the vehicle first reaches an RPM above idle. Its sorta backward from what the manual says - it should come on when the vehicle is started and go off when RPMs increase - which it was doing with my old instrument cluster.

Do I have a bad oil pressure sender too or have I induced another problem?

Any advice would be helpful.