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1989 38-200 Alternator Wiring

e30plus

New Member
I am adding a battery to my house bank and adding a Blue Sea battery Isolator. The problem is that I am not sure how the Alternator is wired. It appears that the charging wire goes from the alternator to the amp meter located in the cockpit instrument panel and from there to the stud on the starter. A battery cable goes from stud to the positive post on the battery. So, to me it looks like the charge goes from the alternator via the amp meter and the starter, to the batteries.
 

Tom Metzger

Sustaining Partner
I am adding a battery to my house bank and adding a Blue Sea battery Isolator. The problem is that I am not sure how the Alternator is wired. It appears that the charging wire goes from the alternator to the amp meter located in the cockpit instrument panel and from there to the stud on the starter. A battery cable goes from stud to the positive post on the battery. So, to me it looks like the charge goes from the alternator via the amp meter and the starter, to the batteries.

Yup, you have it figured out correctly. Electrically, it's strange, but if you are assembling boats it is very cheap.

Several years ago I came up with some modifications that improved the circuits. A while back it got purged from the site with a lot of other good info, but was resurrected by Christian Williams here:

http://www.ericsonyachts.org/infoex...-Universal-Diesel-Wiring-Modifications-How-To

If you have questions let me know.
 
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Tom Metzger

Sustaining Partner
Check out this website. Its very detailed about some issues with the Universal 5432 when it comes to the alternator charging wiring.

http://www.pbase.com/mainecruising/universal_wiring_harness_upgrade

Maine Sail does a good job of dramatizing what I wrote in 2001.

He doesn't like the ammeter (with lots of company), but I do. It tells me that the glow plugs are heating. I have since installed an alarm buzzer for low oil pressure and high temperature which changes tone when the glow plugs are energized which negates my need for the ammeter. I included a diagram showing a voltmeter replacing the ammeter. [I wonder if anyone has ever looked at that voltmeter after it was installed. :rolleyes: ]

He also doesn't reuse the disconnected orange #10 wire to provide more voltage to the solenoid coil. This saves a lot of grief as the switches age. My "Change B".

After removing the charging current from the wiring harness the "trailer" connectors are not overloaded. Being in fresh water I wouldn't replace them, and if in salt water I would probably just tape them up if they are in good condition to avoid salt corrosion. Of course, no harm can come from replacing them, assuming it's not a sailing day.

Overall, you won't go wrong following Maine Sail's advice on the many topics on his website. He is a professional which means he has financial liability which makes him more risk-adverse than most boat owners and his work has to look better. Frequently there are less expensive ways to do a job than what he recommends or shows in pictures.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
I agree about the trailer connectors. Pull them apart and inspect. If there is nothing wrong with them, there is nothing wrong with them.

That was the case on the current boat.
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
Trailer Connectors and Wiring "Change D"

Ditto on the trailer connectors. Admittedly, It was a terrible idea to run the 50A (600W) charging circuit from the alternator through the trailer plugs. This current is continuous, and, even without corrosion on the connectors, generates a lot of heat (not to mention a 70 or 100 A alternator!). The 21 A (250W) glow plug circuit is probably not ideal for the trailer connectors, but it is a momentary-use circuit, and not likely to generate much heat in one minute or less of use (even with a little corrosion). Pull these two circuits out (and also the black ground wire, which has to carry the full load of the engine panel), and I think the trailers connectors are fine (and pretty handy) for the remaining low-load circuits. Coat the pins lightly with dielectric grease (auto part store), tape around the connector to prevent moisture, and I think you're good to go.

Depending on the specifics of the boat, one other circuit that might need a little inspection is the purple (key-switched positive) circuit. On my boat, this wire went to 3 components: the alternator excitation circuit, the fuel pump, and the hour meter. The add-on splices to the original purple wire were in poor shape. I don't know what the amperage draw is on on a Facet fuel pump, but I wonder if it's a little high for this circuit. I've been considering a "Change D" (to add to Tom's excellent wiring modifications) and connecting the unused red-yellow wire (previously from the starter solenoid in Tom's "Change B") to the "on" position of the key switch and then directly to the fuel pump. This would leave the purple wire powering only the alternator excitation and hour-meter circuits. Any comments?

Added: I just looked up the Facet 476459E fuel pump. It says average draw is 1.6A. I suppose amperage varies between pump start-up and continuous operation, and may also differ depending on whether the engine running or not (fuel flowing to the injectors vs fuel just being pumped through the return line). I wonder if it's a bad idea to have the alternator excitation circuit sharing the purple wire with a varying-load fuel pump, even if the total amperage is not a problem.
 
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Tom Metzger

Sustaining Partner
Hey guys - You can over think this topic.

Take the battery charge current out of the cable and all is fine. The ground wire is not a problem because the glow plugs, the solenoid, the alternator field, and the fuel pump are grounded through the engine block. This leaves only the blower motor and the gauge lights. You would do more good running a large wire from the alternator negative terminal to the main engine block ground.

Ken's "Change D" is misguided. Changing the color of a wire from purple to yellow-red does not make an electrical change. It's still a small, but adequate, wire. He really missed was that the purple also wire powers the glow plugs, the solenoid coil, and the blower. This is not a problem because the switch is rated at 35 amps as I remember.
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
Hey guys - You can over think this topic.

Yeah, that's mostly what we do here on the Ericson forum......

Take the battery charge current out of the cable and all is fine.........
The ground wire is not a problem because the glow plugs, the solenoid, the alternator field, and the fuel pump are grounded through the engine block. You would do more good running a large wire from the alternator negative terminal to the main engine block ground.

Excellent point Tom. One that I missed. Does the alternator itself though not ground, as well, via its metal-to metal contact with the engine?

Changing the color of a wire from purple to yellow-red does not make an electrical change. It's still a small, but adequate, wire. He really missed was that the purple also wire powers the glow plugs, the solenoid coil, and the blower. This is not a problem because the switch is rated at 35 amps as I remember.

How odd, I was sure yellow wires carry more current than purple ones.....

I think a little clarification is needed here. By my understanding, the whole engine panel is powered from the positive "on" post of the key switch. Nothing on the panel works until you turn the key (except, on my boat, the blower, which works any time either battery is selected on the battery switch). It is the "on" post of the key switch that powers the glow plug switch, stater solenoid switch, and all the gauges, lights, etc on the panel. The purple wire (inferior color though it apparently is) just carries power from the "on" post of the key switch back to the engine compartment where it powers (on my boat) the alternator excitation circuit, the fuel pump, and the hour meter.

I'm still curious as to whether it's okay to have an alternator excitation circuit and a motor driven pump on the same (purple) wire, or whether the two components would be better served by separate wires (by dedicating the unused yellow-red wire to the fuel pump). Comments?
 
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Tom Metzger

Sustaining Partner
Excellent point Tom. One that I missed. Does the alternator itself though not ground, as well, via its metal-to metal contact with the engine?

Yes, it does. That said, it is important to reduce the engine's resistance if you use a high output alternator. Not so much with the OEM alternator. I have never measured the voltage drop from the alternator to the battery negative, but the separate heavy wire is something that Balmar says to do. I only mentioned it because you were concerned with the ground current in the wiring harness.

How odd, I was sure yellow wires carry more current than purple ones.....

Yes, I agree, but this is a yellow/red wire. :nerd:

I think a little clarification is needed here. By my understanding, the whole engine panel is powered from the positive "on" post of the key switch. Nothing on the panel works until you turn the key (except, on my boat, the blower, which works any time either battery is selected on the battery switch). It is the "on" post of the key switch that powers the glow plug switch, stater solenoid switch, and all the gauges, lights, etc on the panel. The purple wire (inferior color though it apparently is) just carries power from the "on" post of the key switch back to the engine compartment where it powers (on my boat) the alternator excitation circuit, the fuel pump, and the hour meter.

Yes, I'll agree again (you're on a roll), but I have no idea what you mean. All connections to the "on" terminal of the switch are colored purple. They go to the gauges, etc on the panel AND to the engine components.

I am wrong about the blower. As you point out the blower switch is powered from the battery connection at the solenoid through the same red wire (#5 on the diagram) as the engine panel. The blower & switch don't show on the engine wiring diagram because they are not part of the engine, but part of the boat. The wire from the switch to the blower should be dark blue on our boats. ABYC standards call for brown/yellow, or yellow if it is not used for ground, or yellow.

I'm still curious as to whether it's okay to have an alternator excitation circuit and a motor driven pump on the same (purple) wire, or whether the two components would be better served by separate wires (by dedicating the unused yellow-red wire to the fuel pump). Comments?

I would point out that it has worked for the past 30 something years on thousands of boats so I guess it has passed the test of time. If you want to use the yellow/red wire I am confident that no one will complain, provided you wrap it in purple tape. :0 OK, painting it with the correct shade of purple would also be acceptable. It's a sin to put wires of different colors on a single terminal.
 

Rocinante33

Contributing Partner
I agree about the trailer connectors. Pull them apart and inspect. If there is nothing wrong with them, there is nothing wrong with them.

One suggestion I have if you are keeping the bad old trailer connector is to add some dielectric grease to the connections to help keep the moisture out.
 

markvone

Sustaining Member
I agree about the trailer connectors. Pull them apart and inspect. If there is nothing wrong with them, there is nothing wrong with them.

That was the case on the current boat.

FWIW, I just eliminated my 37 year old trailer connectors last winter when I rehabbed my engine panel. They were in perfect condition. A PO added a 100A alternator around 1995 or earlier and disabled the ammeter and it's wiring at the same time.

Mark
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
Yep. The rat's nest of wires the trailer plug is connected to worries me more than the plug itself...

20180328_181835.jpg
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Ken,
I used to worry about a similar "rat's nest" behind our engine panel till I decided one day to check, clean and re-tighten those connections. I learned that each of those wires serves a purpose, can be traced to its source and works just fine as long as its clean and tight with no corrosion.
While it may look better to have it neatly organized, I'm not convinced it's worth the effort or would provide any advantage. But I may be wrong....
Frank
 
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