My oil pressure gauge is fluctuating from 50 to 80 lbs. It seems like it is a electrical problem. I was going to change the sending unit from my stbrd side to port side and see if it does the same thing. Well, there is no room to get at the portion of the sender to unscrew it. I tried a 90 deg open end wrench bu it does not get a good ennough grip to unscrew. It is very tight. I tried a vise grip but it will not stay on the unit. I have twin engines and there is no room for my arm to get around the wires and heat exchanger. I do not want to pull out the heat exchange because I am not sure if the sender unit is the problem. Anybody famililar with the wiring of the sender. I was thinking it could be the alternator. Volvo does some strange stuff with the alternator circuit and tachometer, etc. Anybody have problems with the oil pressure and volt meter. When it goes up and pegs the guage, sometimes the volt meter acts up and if I turn on the dash light it moves in a different directioin. Electrical problems are driving me nuts. Any help or suggestions are welcome. I hope I described the problem. John the mechanic said he has only changed one since he worked on Volvos.