I have had this problem with my boat four years now and no one can find the problem. I have 2005 37PC Volvo D6. After starting the port motor alternator will only show 11.9 volts. After running for about 10 minutes the Voltage comes up to "normal" levels. My local volvo dealer basically said they can do no more for me. (just gave up) has any one had this problem and found a solution?
I found the problem! There is a small resistor on the back of the alternator it has a brown wire attached to a lug on the alternator then goes into a small block where a red and blue wire come out (not sure colors are correct do not have part in front of me) which goes into a small connector. As soon as I switched the resistors from one side to the other the problem went away!!!. I have ordered the part from Marine Parts Express do not have it yet but if it is correct I will post the part number here.
I found the problem! There is a small resistor on the back of the alternator it has a brown wire attached to a lug on the alternator then goes into a small block where a red and blue wire come out (not sure colors are correct do not have part in front of me) which goes into a small connector. As soon as I switched the resistors from one side to the other the problem went away!!!. I have ordered the part from Marine Parts Express do not have it yet but if it is correct I will post the part number here.