I've had a similar problem with my MD2B (100hrs). The alarm would go off
intermittently at various rpm. After replacing the sending unit (at $28) it
still happened. I added a pressure gage and found the oil pressure was
normal and it was the alarm module (Volvo OEM). They want $140 for a new one
and I am going to add one that is after market for about $40. Right now I
have the alarm module disconnected.

Steve
s/v Good Intentions