Low output from alternator... will this work to finish my trip?

[basssears]

This a bit repetitive, but I'm a little "out in the woods" cruising the Gulf Islands for two weeks and want to know if I'm about to do the right thing... so yes, hand holding, sorry.

Back story is:
1) Output from alternator is low... when I test voltage with engine at ~2,000rpm (using simple test gauge in cigarette lighter) I get ~12.75 volts... not sure what I used to get, but I know enough to know this isn't sufficient.
2) Alternator is basic, internal regulated (AFAIK, I can't tell what brand / model alternator is, but back of alternator has what appears to be Motorola regulator on it, picture attached). I have tested the output from the back of the alternator itself (thanks to Gord's Basic Alternator Testing post) and when I throttle up I get 14 volts from back of alternator. So, my conclusion is I have some sort of voltage drop in the wiring from alternator to batteries.

My problem is two fold... one is a personal problem, which is that our last cruise ended with unplanned 4 day stay at marina while a water pump was replaced... if I cut this cruise short with an electrical problem it goes poorly with the admiral. We are currently three days sail from home as it is, have plans for another two weeks of sailing.

Second problem is the technical one... basically, I can't figure out how the wiring works once it goes from the alternator. I have a ground (pretty obvious) and an orange hot output from the alternator... orange wire gets bound up with a whole bunch of wires and (appears, based on connectivity testing) to go up to behind my electrical panel to amp meter and then ignition switch and from there who knows where... I truly don't understand HOW charging power it getting from alternator to batteries. If I did I could try to trace wires, but even then the wires are in a whole big bundle that then disappears through a truly inaccessible spot before reappearing inside my electrical panel.

SO... here's the hand holding part... I am thinking I will sail / motor along tomorrow to Ganges on Salt Spring (I am getting 12.75 volts when at engine speed, so a decent amount of charging happens), where I can plugin and bring my batteries back up to proper levels, and where I will then buy some 6 or 8 gauge wire (not a very long run, and best I can figure this is a 50A alternator) and wire my alternator directly to my house bank, as detailed in this post: Alternator Wiring Help). I assume at that point to avoid fires I disconnect my orange wire from the back of the alternator.

Does this sound like an OK plan? Will it work? Will it charge my house bank (and by extension, when my battery switch is on ALL, my start battery) properly to get me through rest of trip? I know I might lose some things like the amp meter on my electrical panel but I never look at that anyway, I just look at voltages when things are running.

Thanks in advance for any advice, if I was at home with my Calder and my tools and all the time to think it through I would try to trace the wire and fix it, but this SEEMS like it can be overcome reasonably easily with a quick bit of wiring.

Any help much appreciated.

-- Bass

[Sailmonkey]

That will work just fine. But don't forget a fuse on the battery end of the wire.


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[donradcliffe]

You could save yourself some wire and go from the alternator to the heavy positive cable to the starter.

[Stu Jackson]

I'm in Maple Bay and would sail over & help you, but it's going to be flooding all afternoon tomorow and I'd never get there!

This is from Maine Sail's article, here:

Universal Diesel Wiring Harness Upgrade Photo Gallery by Compass Marine How To at pbase.com

Bypass The Orange/Red Circuit
Here's the quick and dirty fix. Try to focus on the red wire between the back of the alternator and the starter post. Simply jump the alternator output to the starter post and disconnect the orange wire. With this jumper the alternator output bypasses the 20+/- feet of teeny tiny 10GA wire and uses the large gauge starter wire to make its way back to the battery switch and then to the battery banks. Minimal voltage drop compared to the 10GA circuit and much less resistance and heat without going through all that small wire and two trailer connectors.


Please note that I generally advise running the alternator output directly to the house bank, not to the starter as shown here. You can then install an automatic combining relay (ACR) or an Echo Charger between the banks to charge both simultaneously. Doing this will remove the potential for fried diodes via the flipping of the battery switch through the OFF position. While not 100% necessary it is a good upgrade,and , as I always say, "while you're in there" might as well.


Even if you choose not to run the alternator direct to the house bank you are far safer with the new jumper than you were before.

You need to be very, very clear on what orange wire you're talking about.

You seem to be hoping, rather than knowing, what you're doing.

Draw a wiring diagram, like this, so you fully understand what and why you're doing. Just like in my post #4 on the link you included!!!


Alternator Regulator Wiring Diagrams - all three Alternator Regulator Wiring Diagrams (all three)

Those diagrams are for the same alternator you have,m from what I can tell.

Good luck. I'm going out to anchor at Genoa Bay tomorrow and Sunday morning, so won't have any internet connection there.

[Larry Florida]

This may be useful to you:

Universal Diesel Wiring Harness Upgrade Photo Gallery by Compass Marine How To at pbase.com

I have the same alternator. Have been struggling with er all summer.

There is a wiring upgrade to the trailer connector you may consider.

[basssears]

Originally Posted by Stu Jackson

I'm in Maple Bay and would sail over & help you, but it's going to be flooding all afternoon tomorow and I'd never get there!

Thanks Although I haven't noticed the currents that much, been spending most of my time trying not to get run down by ferries

Originally Posted by Stu Jackson

You need to be very, very clear on what orange wire you're talking about.

You seem to be hoping, rather than knowing, what you're doing.

I hope I know what I'm doing?? So the "orange wire" I'm talking about is secured onto the post on the back of the alternator that is labeled "POSITIVE / OUTPUT" in the attached photo... that is the one that, when I put my test meter between it and the post labeled "NEG. / GROUND" I get 14+ volts, so that seems right to me, no?

[Stu Jackson]

Originally Posted by basssears

I hope I know what I'm doing?? So the "orange wire" I'm talking about is secured onto the post on the back of the alternator that is labeled "POSITIVE / OUTPUT" in the attached photo... that is the one that, when I put my test meter between it and the post labeled "NEG. / GROUND" I get 14+ volts, so that seems right to me, no?

That orange wire (should go) (goes) to the starter, and the C post of the 1-2-B switch, ASSUMING the boat is wired OEM.

Try this:

OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

What boat, what engine?

If you understand the concept, then you should be OK, but we have NO idea how the rest of the system is wired, so I'm passing on knowledge you should be able to use, NOT telling you what to do.

[basssears]

Originally Posted by Stu Jackson

That orange wire (should go) (goes) to the starter, and the C post of the 1-2-B switch, ASSUMING the boat is wired OEM.

That sounds about right... it goes from alternator to amp meter to ignition switch and then I lose it because the orange stops and there's lots of splicing etc going on.

Originally Posted by Stu Jackson

What boat, what engine?

If you understand the concept, then you should be OK, but we have NO idea how the rest of the system is wired, so I'm passing on knowledge you should be able to use, NOT telling you what to do.

Sorry, should have specified at beginning... it's a 1988 Gulf 32 with the Westerbeke M40 (i.e. Universal 5432) engine. It appears to have the same wiring glitch that MaineSail writes about in the links listed above. Boat is new to me, for all I know it's always been like this, this is just the first long cruise we've been on without shore power and with some newer power demands so I think I'm just now noticing the under charged batteries.

Heading to Salt Spring today with access to marine shops plan is to hopefully have someone crimp up a nice jumper for me between by alternator and my starter as detailed by MaineSail:
Universal Diesel Wiring Harness Upgrade Photo Gallery by Compass Marine How To at pbase.com

[Bleemus]

If you have the ammeter then I am willing to bet the trailer plug going to it is fried. That wire is undersized and prone to failure.

Why not fix the voltage drop? Forgive me if I am being rude but those terminals look filthy. Clean them up.

If you don't know what you are doing or looking at then disconnect the batteries and then clean every single heavy red wire connection terminal you can find on the whole boat till it looks new and then try to bypass the ammeter with properly sized wire.

[jeepbluetj]

If you have the ammeter, I'd bypass it (why run 20' of cable just to measure current)

Also, get a cheap multimeter and test the voltage at the alternator. If it's good there, you know it's wiring. If it's not - it's the alt or regulator.

[tinkrman69]

testing your charging volts at a cig lighter isn't very reliable. Test it at the battery. Better yet test it at the amp meter. And also, is the amp meter showing amps in or out. on the right sid or left side of zero. If it's showing a substantial amount of amps on the right side then check if the orange wire is getting hot or warm. If yes change the wire, just cut both ends and run a new wire from the alt to the amp meter. the wire can still show connectivity, but be degraded enough to not be able to handle the amps/voltage. meaning the more am[s you draw the lower the volt will go.

In an earlier post a trailer connector was mentioned. you'll be bypassing that and it will have to be addressed at a later date, as it is a known fault. but simply running a new orange wire will get you by till you get home. re-routing it away from the panel will cause other things to go out.....not good.

[SeaSon]

I had an ammeter on the helm, didn't like the idea of running power all the way up then back to the batteries so I ran one wire to the helm for power there, changing the ammeter to a voltmeter, and a separate wire to/from the alternator to the house bank. This is a logical description, actual wiring was using a terminal block in the engine room as the junction of alternator, battery and helm power.

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[basssears]

Originally Posted by jeepbluetj

If you have the ammeter, I'd bypass it (why run 20' of cable just to measure current)

I will bypass it for sure. Part of what was confusing me about this whole thing is that I would never have done something like this (long run of undersized wire) so I couldn't wrap my brain around what the OEM setup was accomplishing (or not).

Originally Posted by jeepbluetj

Also, get a cheap multimeter and test the voltage at the alternator. If it's good there, you know it's wiring. If it's not - it's the alt or regulator.

Have tested voltage at the alternator with my multimeter, I get 14 volts, so it's not the alt or regulator, it's the wiring.

[jeepbluetj]

Originally Posted by basssears

Have tested voltage at the alternator with my multimeter, I get 14 volts, so it's not the alt or regulator, it's the wiring.

Then I'd do what a previous poster suggested - wire from the alt to the big battery cable on the starter. Simple fix to let you finish the trip.

[basssears]

Thanks to everyone for their input, definitely steered me the correct direction.

As I mentioned, I was getting 12.7 volts at the batteries when throttled up. Went to the marine shop here in Ganges, Salt Spring and had a 4 gauge jumper made up with the right ring terminals, installed it between alternator and starter, removed old orange wire from alternator and fired 'er up... 13.4 volts at the batteries at idle, 13.8 when throttled up.

Does sort of surprise me the old system lasted this long and no one ever had an issue with it before, but of course that probably goes a long way towards the "3 new batteries" in the sale listing when we bought her last year.

Thanks everyone, a world of help, much appreciated.

-- Bass