Mainsail's Universal Diesel amp meter bypass

Stu Jackson · Mar 15, 2015

1. You'd best ask Maine Sail directly.

2. Why would you do the mod and not do everything he suggests?

3. Here's the WHY about the original wiring: OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

Assuming you have the stock setup, and are moving the AO to the house bank, if you truly understand the logic about the wiring, the orange wire between the starter/solenoid and the alternator makes sense in the old scheme, but not the new one, if you are switching (pi!) between a charge 1-2-B switch and a use switch.
http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

TENACITY CS36T · Mar 15, 2015

No the ammeter won't work, I believe the red and orange are in series to,and from the ammeter, and that's the problem, that type of meter does not use ashunt and is rated for the expected loads, but the wiring isn't.

Stu Jackson · Mar 15, 2015

Ammeters & Shunts 101 http://c34.org/bbs/index.php/topic,6032.0.html

Stu Jackson · Mar 15, 2015

If this is what you're doing (the quick fix), then it's explained pretty clearly.

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.

And yes the ammeter will no longer work.

Maine Sail · Mar 15, 2015

Skipper said:
For electrical experts....

I'm doing this mod today:
http://www.pbase.com/mainecruising/universal_wiring_harness_upgrade

I'm wondering if I jump the alt as described but leave the orange wire connected, will the amp meter still register, yet without the big charging load going through the old circuit.

Also, seems that this mod would decrease the load on the alt(?)

No it won't work...

You replace the ammeter with a volt meter or you install an ammeter with external shunt, and do so in a safe manner, and in the amp rating needed for that circuit.........

Mod will not decrease the load on the alt but it will greatly help your batteries attain the proper voltage. That circuit leads to high resistance and voltage drop at the battery end but the alt still works just as hard...

Stu Jackson · Mar 15, 2015

Skipper said:
Except for my question.

I'm glad you got your answer, but if you disconnect it as Maine Sail stated, then why would you assume it would work?

Just askin', not trying to argue.

Stu Jackson · Mar 15, 2015

Skipper said:
\

Edit: I didn't assume it would work if disconnected, I was wondering if it (ammeter) would work if stayed connected but with the jumper.

Now I get it. Your question, that is.

Think of the circuit. Would current flow through the shunt (and therefore the ammeter) if the circuit had bigger wires further "up the food chain?"

Hmm, I'll have to think about that, but golf is in a playoff!

Nice background you shared.

Here's some more sources of info for you:

Critical Upgrades http://c34.org/bbs/index.php/topic,5078.0.html

Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

http://www.c34.org/wiki/index.php?title=Diesel_Engine

Different boats, same danged SYSTEMS. Poke around our website, parallels and supports and links to Maine Sail's excellent info.

Allan12210 · Mar 15, 2015

Maine Sail said:
No it won't work...

You replace the ammeter with a volt meter or you install an ammeter with external shunt, and do so in a safe manner, and in the amp rating needed for that circuit.........

Mod will not decrease the load on the alt but it will greatly help your batteries attain the proper voltage. That circuit leads to high resistance and voltage drop at the battery end but the alt still works just as hard...

This thread was especially timely for me. I am now sold going direct from the alternator to the house bank with the properly sized large gauge wire (numerically small number). I missed the article the first time around (or the 10th, who knows why). I have been flying blind forever utilizing an ammeter and the 10 ga wire. In the last two months since I installed a Balmer Smart Gauge and have seen that my batteries don't seem to charge while motoring. Just today, I returned from a cruise-out where I deliberately left the shore charger off for 2 days. My SOC was 86% when we left the dock this am and motored for 2 hours. After arriving I checked the SOC and it was 84%! The charging voltage while running at 3000 rpm per the Balmer was 13.8 V (duh, living and learning). The batteries prior to leaving (at 86%) were about 12.5 V. I'm just using the stock Hitachi alternator that came with my 3GMF22 engine. I'm charging 4 Trojan 6V batteries and via a combiner, a Group 27 starting battery. All flooded (starter is a maintenance free).

I already have a voltmeter on my (home made) panel along with oil pressure and engine temperature. I would sure like to continue with a functional ammeter but at least today can't seem to find a 2" round gauge style ammeter with an external shunt. Any sources come to mind?

Allan

centerline · Mar 15, 2015

Skipper said:
I was wondering if it (ammeter) would work if stayed connected but with the jumper.

electricity will always take the path of least resistance... and the whole point of adding the large red wire is to lower the resistance so the electricity can flow easier thru it, rather than thru the higher resistance orange wire.... if you left the orange wire in the circuit, you may get a residual reading, but i doubt it, and if you did it would never be accurate...

if you need to know the amps for testing and troubleshooting, you could get an old style inductive meter and read from the red wire without any connections at all....

centerline · Mar 15, 2015

Allan12210 said:
I would sure like to continue with a functional ammeter but at least today can't seem to find a 2" round gauge style ammeter with an external shunt. Any sources come to mind?

Allan

an external shunt or remote shunt?... they can be different.

here is a bluesea ammeter with a remote shunt, which is better...

scroll down thru it to see part numbers....

Allan12210 · Mar 16, 2015

centerline said:
an external shunt or remote shunt?... they can be different.

here is a bluesea ammeter with a remote shunt, which is better...

scroll down thru it to see part numbers....

Thanks Centerline for the link. Unfortunatly Blue Sea meters have a rectangular face and I have round, weatherproof covers for my gauges. I was planning on converting the wiring (which I will do anyway), then with a remote shunt in series with that, use the existing 10 ga wire up to the existing ammeter location. There I would replace the current ammeter with a new one. Maybe I could take the old one apart and relocate the internal shunt?

The search continues.

centerline · Mar 16, 2015

Allan12210 said:
Thanks Centerline for the link. Unfortunatly Blue Sea meters have a rectangular face and I have round, weatherproof covers for my gauges. I was planning on converting the wiring (which I will do anyway), then with a remote shunt in series with that, use the existing 10 ga wire up to the existing ammeter location. There I would replace the current ammeter with a new one. Maybe I could take the old one apart and relocate the internal shunt?

The search continues.

check with your local auto electric rebuilder.... where they rebuild starters and alternators, they should know suppliers that carry what you want...

Maine Sail · Mar 16, 2015

Allan12210 said:
Thanks Centerline for the link. Unfortunatly Blue Sea meters have a rectangular face and I have round, weatherproof covers for my gauges. I was planning on converting the wiring (which I will do anyway), then with a remote shunt in series with that, use the existing 10 ga wire up to the existing ammeter location. There I would replace the current ammeter with a new one. Maybe I could take the old one apart and relocate the internal shunt?

The search continues.

If you want a true ammeter they are best installed inside the boat. The engine panel is really only well served to show you whether the alt is working or not and a volt meter does this. The Blue Sea Ammeter fits a standard 2" hole but for the cost I prefer to see them down below...

The best value for an ammeter, which comes with a 500A shunt, is the Victron BMV-600 battery monitor but it does a lot more than just monitor amperage.

Mainsail's Universal Diesel amp meter bypass

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