Author Topic: Yannmar's alternator  (Read 6625 times)

marioxp

  • Able Seaman
  • ****
  • Posts: 176
  • Karma: +1/-2
  • Boat Model: Bavaria 36
  • Boat Year: 2003
Yannmar's alternator
« on: March 23 2023, 13:15 »
This isn't about Bavaria, it's not even about a sailboat anymore.
A friend has a small excavator and needs to change the alternator. It is an alternator for Yannmar's 18 hp diesel engine. He got a working alternator but someone cut the wires and he can't tell which wire is positive and which is negative, both wires are blue. We tried to measure the voltage while turning the rotor clockwise by hand. But the voltage fluctuates between positive and negative, and we cannot tell whether it is positive or negative.

Is there any way to determine which wire is positive and which is negative?

Yngmar

  • Administrator
  • *****
  • Posts: 1532
  • Karma: +18/-2
  • Boat Model: 40 Ocean
  • Boat Year: 2001
Re: Yannmar's alternator
« Reply #1 on: March 23 2023, 14:07 »
Not Bavaria related, let's not make this a habit please.

That said, all signs point to this being an unrectified AC output straight from some windings, so there is no positive or negative, which is why the wires are the same colour and why you measure exactly that output. Therefore it doesn't matter which way around you connect them. The other part it connects to presumably contains the rectifier diodes.
Sailing Songbird  ⛵️ Bavaria 40 Ocean (2001)

marioxp

  • Able Seaman
  • ****
  • Posts: 176
  • Karma: +1/-2
  • Boat Model: Bavaria 36
  • Boat Year: 2003
Re: Yannmar's alternator
« Reply #2 on: March 24 2023, 14:12 »
I'm sorry, I didn't know where to put this question.

My apologies.

Laysula

  • First Mate
  • ***
  • Posts: 70
  • Karma: +0/-0
  • Boat Model: 350 lagoon
  • Boat Year: 1994
Re: Yannmar's alternator
« Reply #3 on: January 29 2024, 09:34 »
I'm sorry, I didn't know where to put this question.

My apologies.

There is a Yanmar engine forum on facebook.