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xxhat · 02-01-2019, 17:53

was working on my battery and reconnecting wires.

Realised that if I start engine and alternator wires are NOT connected I will burn alternator up.

How do I identify which wires are from the alternator to the battery ?

The wiring harness from the engine (Betamarine) is impossible to access.

Thanks,

jim

Sailmonkey · 02-01-2019, 18:38

Look at the back of the alternator and follow the big wire to where it’s connected.

**Wotname** · 02-01-2019, 18:56

Quote:

Originally Posted by xxhat

was working on my battery and reconnecting wires.

Realised that if I start engine and alternator wires are NOT connected I will burn alternator up.

How do I identify which wires are from the alternator to the battery ?

The wiring harness from the engine (Betamarine) is impossible to access.

Thanks,

jim

No, you won't damage the alternator if you run the engine without any wires connected to the alternator. Just make sure the disconnected wires are insulated from each other and the engine chassis.

dmkkeng · 02-01-2019, 20:44

I'm not sure if you will damage your alternator if you run your engine without the alternator being connected to a battery however it wouldn't be my first choice to do this.

You could use an ohm meter to check the continuity of the wire that is connected to the positive terminal on the back of the alternator, you may need to use a long piece of wire to extend the leads of your meter.

I would feel more comfortable making sure the alternator was connected to the battery before I ran the engine.

Another possible option (depending on the type of alternator) would be to disconnect the exciter wire, without it there is no output from the alternator.

**Jim Cate** · 02-01-2019, 22:03

Running the alternator disconnected won't harm it at all. What harms them is to disconnect the output from the load whilst running, as in turning the battery switch to "off" while running. This generates a voltage spike that destroys the diodes.

Jim

**GordMay** · 03-01-2019, 04:38

Quote:

Originally Posted by Jim Cate

Running the alternator disconnected won't harm it at all. What harms them is to disconnect the output from the load whilst running, as in turning the battery switch to "off" while running. This generates a voltage spike that destroys the diodes.
Jim

Indeed.

Alternator Wire identification tips:

Remote voltage sense (S): Small gauge wire 16AWG or larger that has voltage present at all
times. Usually is connected directly to battery positive.

Ignition excite (I): Small gauge wire 16AWG or larger that has voltage present only when the
ignition switch is in the run mode. Check for an alternator warning lamp. If warning
lamp is present then this wire can be connected to the alternators lamp terminal. If not, then
insulate, secure and do not connect to the alternator.

Positive cable: Large gauge wire 4AWG or larger that has voltage present at all times. Usually red
in color.

Negative cable: Large gauge wire 4AWG or larger connected to battery or chassis ground.

AC or Relay (R) cable: If none of the above test help identify a wire then it could get connected
to the alternators AC terminal. Usually this wire operates a relay or tachometer and should be
verified before being connected to the alternator.

More ➥ http://www.prestolite.com/literature...tor_wiring.pdf

xxhat · 03-01-2019, 05:50

Thanks to all who replied.

I had an idea. How about I connect a multimeter to existing unconnected wires then start the engine and see if there is voltage. Where there is voltage will be the alternator wire.

Any problems ?

Thanks

Jim

xxhat · 05-01-2019, 02:05

Thanks to all who replied.

I had an idea. How about I connect a multimeter to existing unconnected wires then start the engine and see if there is voltage. Where there is voltage will be the alternator wire.

Any problems ?

Thanks

Jim

smac999 · 05-01-2019, 02:57

It's likly not going to have power. It needs power to start running.

Likly the wire goes from alt to starter post. That is most common by default.

**GordMay** · 05-01-2019, 03:53

Your boat builder MAY have utilized the ABYC Colour Code system.
➥ https://www.pacergroup.net/abyc-colo...SAAEgLmMfD_BwE

MarkusK · 08-01-2019, 17:42

Quote:

Originally Posted by Jim Cate

Running the alternator disconnected won't harm it at all. What harms them is to disconnect the output from the load whilst running, as in turning the battery switch to "off" while running. This generates a voltage spike that destroys the diodes.

Jim

If that happens, bring your alternator to your local car mechanic. Mine replaced my diodes for under $100 cdn.

pcmm · 08-01-2019, 17:58

Quote:

Originally Posted by MarkusK

If that happens, bring your alternator to your local car mechanic. Mine replaced my diodes for under $100 cdn.

I replaced the alternator on my yanmar for $100 (100amp hitatchi type)

neworleansrich · 08-01-2019, 18:43

Get the best book ever written about alternators:

The 12 Volt Doctor's Alternator Book (illustrated) Paperback – 1986
by Edgar J. Beyn

Seriously!

DougR · 08-01-2019, 19:38

Suggest you get a wiring diagram for your engine before you:
- destroy the alternator
- start an engine room fire
- destroy the wiring loom on the engine

Or you could bring in an electrical technician to hook up the alternator for you.

Couple of other thoughts....
- Cell phone pictures before disassembly help with reassembly
- some alternators will self energize even without the energize lead hooked up, so starting the engine without the wiring attached to the alternator may still result in alternator damage.

DougR