Alternator Questions

RonD2 · Post by **RonD2** » Thu Aug 24, 2017 1:28 pm

My M38 was converted to 12v. Has a ammeter in the dash (+/- 50 amp scale). I've got a bad 3-wire Delco 10SI 63 amp alternator and am considering rebuilding or replacing it with a one-wire 10SI (self-exciting) set up, with the "low rpm" cut-in on charging, which seems to be a good thing for a L134 motor so it doesn't have to be goosed to 2500-3000 rpm to get it to start charging.

My alternator experience is none. There's a lot of back-and-forth and pro's and con's of 1-wire v. 3-wire 10SI alternators on the interweb. I'm leaning towards the one-wire set up, and can't really see any good reason not to do it.

So I thought I'd ask for second opinions here before pulling the trigger. You're advice is always appreciated.....including what alternators or re-build kits are worth owning and which aren't.

I'm guessing there's enough M38's out there with 12v conversions to make this a legit question? .......waiting for advice "Take it to the Chevy forum!"..........

chuck · Post by **chuck** » Thu Aug 24, 2017 2:56 pm

I have a 12si one wire on my M38A1 with a 4.3 Chevy motor, and a 10si converted 24v single wire on both my M38 and M37
All have been trouble free.

4x4M38 · Post by **4x4M38** » Thu Aug 24, 2017 5:04 pm

And you can lose that ammeter and replace it with
a voltmeter!

RonD2 · Post by **RonD2** » Fri Aug 25, 2017 8:14 am

Not as long as it still works! Besides, I like the "old school" look of it and how many folks who don't know what it measures. I usually tell them "flux capacitance".

The M38 is, after all, a time machine.

RonD2 · Post by **RonD2** » Fri Aug 25, 2017 8:40 am

Another question if you please: I've found regulators with charging value set points of 13.8 and 14.8 volts. Any suggestions? From research, I'm leaning towards the 13.8 volt model as being easier on battery longevity. Thanks!

Post by **wesk** » Fri Aug 25, 2017 8:50 am

The shunt that originally supplied the sense voltage to the military amp meter was in the military voltage regulator and carried to the gauge on wires # 8 & 9. When you switch to an alternator you loose the shunt and wire's 8 & 9 which ran from the old voltage regulator's shunt to the amp gage become useless. So unless you install a shunt rated for that gage between the new alternator and all loads it will not give you any info at all. Since the Army made the switch to the volt meter in the late A1's and M170 I see no reason to keep yourself in the stone age.

RonD2 · Post by **RonD2** » Fri Aug 25, 2017 9:08 am

Hi Wes. Thanks, but that's too late for me. When I said my M38 had been converted to 12v I should've also said it means the truck doesn't have a M38 wiring harness. The previous owner put in what looks like a fairly high quality store bought harness for a CJ (cloth covered colored wires) including turn signals. No military wire number tags anywhere. It also has what looks like a CJ 12v gauge set on it, close enough to a semi-military look to suit me anyway. I believe the ammeter is a direct read (no shunt) meter as far as I can tell and have wired it that way. I haven't juiced it yet, so if it explodes when I do I'll know for sure.

The previous owner had the ammeter wired like a voltmeter (didn't work naturally) and the fuel gauge wired wrong (also didn't work). I've been going through the harness stem to stern replacing the shaky CJ-style connectors with military Packard connectors, adding and fixing some goofy grounds, and increasing wire gauge size in a few places. Also installing a master battery cut-off switch (military type). Replaced the CJ keyed ignition switch that was put in a huge hole in the gauge panel where the hi-beam indicator light is supposed to be with a 3-terminal military switch (Off-On-Mom) back where it belongs. The horn and horn switch have Douglas connectors and I'm using them. I've drawn out a schematic and am debating putting wire number tags on everything (using the military wire number table). At this point, I doubt I'll ever put the truck back to 24v (too much $$$), instead, am looking for a solid, safe, and reliable 12v set up.

Post by **wesk** » Fri Aug 25, 2017 9:23 am

I would make sure that amp meter was an internal shunt amp meter before I considered running full system amperage loads thru it. You should be able to ID the amp meter by manufacture and part number and get a solid answer before you throw the juice to it.

RonD2 · Post by **RonD2** » Fri Aug 25, 2017 10:00 am

Yes, darn good advice. As near as I can tell the ammeter is an El-Cheapo ($18) model common to Omix-Ada -- identical to this one:

http://www.ebay.com/itm/Ammeter-OMIX-17 ... SwYIxX2Dhf

The problem is I haven't had any luck finding any technical information about this gauge. Any clues where to look would be helpful.

Post by **wesk** » Fri Aug 25, 2017 10:15 am

Item specifics
Condition: New
Quantity Sold: sold individually
Face Color: Black w/White Pointer
SKU: OMX:17210.01
ModDate: 2014-07-31
Brand: OMIX
Amperage: 50 AMP
Manufacturer Part Number: 17210.01
Size (in.):
OEM UPC: 00804314009779
Harmonized Tariff Code (HTS): 9026106000
Position: Inside
MSDS Required Flag: N
Fitment Footnotes: Cj-3;

This would ID it as a replacement for a stock 6 volt CJ3A but most web entries ID for the 41 thru 56 Willys jeeps.

Here's what a buyer of that gauge says about his experience with it:

When not connected, my needle points slightly to the left, but as you can see, it wasn't designed to get a precise reading. There is no light for nighttime driving, but I'm okay with that. The terminals in the back are long and exposed, so be careful how you install it. If those terminals short to a ground (like the frame or most metal parts) you could start a fire if you don't use a fuse or breaker. Finding installation instructions was a terribly long search, so here are my instructions: Use 8 or 10 gauge wire. Everything should run through the ammeter except the starter (which requires the 2 or 4 gauge wire and would fry the ammeter). The battery and starter are on one side of the ammeter. The alternator and everything else are on the other side of the ammeter. I had to be creative as the alternator and many components were originally connected to the starter. This measures the flow of electricity from or to the battery (except the huge amperage required to start the car). When the needle is to the left, your battery is draining. When it is charging (for a few minutes soon after starting the car), the needle will be to the right. Normally, the needle should be at or near zero. If the engine is not running and the dome lights are on, it should point slightly to the left. If the engine is off and the headlights are on, it should be significantly to the left - maybe 20 amps. For a minute or two after starting the car, the needle might be 5-15 amps to the right (charging). When you turn things on and off, the needle might flicker one way or another before the voltage regulator adjusts the alternator. When stopped at a red light or idling, some cars might drain the battery a little, but should gently charge it again at higher rpms. If the ammeter is not showing normal readings, something somewhere is wrong which might drain or fry your battery - possibly the voltage regulator which is often built into the alternator. Most cars don't have an ammeter any more because of the fire hazard. If you cut or short that 8 gauge wire connected directly to the battery can deliver a lot of electricity even with a fuse. Even with a fuse you could get a nice firework shower of sparks before the fuse blew. Be careful and smart.

Personally I do not care for internal shunted amp meters. They force you to bring the wiring for all the system loads except the starter to a small frail unit mounted in the dash. If your jeep has a CJ harness in it, it should also have a fuse panel. If so I would buy an external shunted amp meter. Mount the shunt near the fuse box and let the amp meter measure the shunts output from a safe distance and at the same time keep all your high current carrying wires on the firewall and not hanging all over the dash. The wires from the shunt to the gage are very low amperage gauging signals only.

Here's another list of specifics:

Brand: OMIX
Part Number: 17210.01
Item Condition: New
Item Description: Ammeter
Manufacturer Brand Description: Ammeter
Quantity Needed: 1;
Fitment Notes: Cj-3;
Position: Inside

Item Specifics:
UPC: 804314009779
Application Summary - 2000: Direct OE replacement Jeep parts and accessories built to the original specifications by Omix-ADA. Limited five year Manufacturer s warranty.
Marketing Description - 2000: Direct OE replacement Jeep parts and accessories built to the original specifications by Omix-ADA. Limited five year Manufacturers warranty.
Product Description - Extended 240: Ampmeter; Inside; Black Face w/White Pointer; -50 To 50;
Product Description - Long - 80: Ammeter Gauge; 41-67 Willys MB/CJ2A/CJ3A/Ford GPW/Jeep CJ3B
Amperage: 50 AMP
Associated Comments - 2000: OE Style
Country of Origin (Primary): TW
Dial (Face Color): Black
Emission Code : 1
Face Color: Black w/White Pointer
Harmonized Tariff Code (HTS): 9026106000
Harmonized Tariff Code (Schedule B): 9030330040
Life Cycle Status Code: 2
Life Cycle Status Description: Available to Order
ModDate: 2014-07-31
MSDS Required Flag: N
NAFTA Preference Criterion Code: D
National Popularity Code : A
National Popularity Description: Top 60% of Product Group Sales Value
Pointer Color: White
Product Description - Short - 20: Ammeter Gauge; 41-67
Remanufactured Part: N
Size (in.): OEM
Warranty Special: 5 Year Limited
Warranty Special UOM: TX
Warranty Time: 5

I noticed you said above:

I believe the ammeter is a direct read (no shunt) meter

All amp meters use a shunt. The meter you describe is internally shunted. A non-direct reading type would use an external shunt usually located in a safer location and closer to the actual loads.

RonD2 · Post by **RonD2** » Fri Aug 25, 2017 11:11 am

Thanks Wes! I stand corrected on ammeter shunt terminology (needed that). The information from the other owner is very useful to confirm that I'm on track.

I have the ammeter wired using 8 gauge wire, carefully crimped and soldered hi-temp terminals, double heat shrunk up to the neck, and fastened with internal-external lock washers. I've been looking for some correct size rubber terminal boots to cover them before I make it hot, but may have to wrap them with some 3M rubber fusing tape in the meanwhile. I've been very careful about managing and securing the wire routes to and from the meter. Fully recognize that any short will result in unintended welding -- or worse.

The starter is wired for action through a solenoid so at least starter current isn't going inside the dash panel to the ammeter. I also have a Klixon 60 amp manual reset main circuit breaker installed on the M38 breaker panel behind the gauge panel. No fuse panel in the CJ harness at all when I got it, but I have separately fused (each, waterproof in-line fuse holders) the horn, the lights, and the turn signal flasher.

May I ask what 12v external shunt ammeter you'd buy?

On my earlier question: 13.8 or 14.8v set point on the alternator regulator?

Your information very helpful and as always --- much appreciated!

Post by **wesk** » Fri Aug 25, 2017 11:17 am

I'd stay with the top shelf gauges normally carried by dealers like Summit racing.

Although 13.8 thru 14.5 is a very acceptable range I prefer to keep it at or below 14.0 volts. I would also incorporate a volt meter (preferably digital) even if you hide it in your glove box. The civil auto industry went to the volt meter for two reasons. 1- it help prevent those terrible underdash fires found with the direct reading amp meters and 2 - It provides much more system info then the amp meter ever did.

RonD2 · Post by **RonD2** » Fri Aug 25, 2017 11:23 am

10-4 !