100 amp alternator

[Heimeken]

Can I just swap one in or will it fry something?

[Stolen76]

IF you don't have an ammeter you could just drop it in. I'd run a new charging cable to the battery or starer solenoid. Use 8 gauge or 6 gauge wire, but bypass the ammeter.

[Horny Toad]

Heimeken,

Where did ya get a 100 amp alternator from? I add dual batts & isolator to my rig and could use more charging power.

HT

[chrism]

You can get a stock alt from a 91 Wagoneer. It should be 95amp. I put one on my CJ a couple years ago.

[jaz459]

is there any extras needed to install? or is it just a drop in?

[mdill]

For 86 + with voltmeters, all you need to do is add a lerger cable from the output terminal
to the starter (or starter relay, depending on year) (6 guage would be prefered) with a fuseable link added to the started side of the cable (two sizes smaller ). Everything
should work fie with this setup.

For 85 -> 7? with amp guage, well no cheap good way to make it work and keep the
amp meter operational. But if you are willing to forgo the amp meter, then the best
way I can think of is to run a new larger cable to the bat side of the starter relay, tie the
origonal output wire off, then remove the red wire from the main firewall terminal
connector (tie it back ,or remove) then move the big yellow wire in the terminal block
to where the red was. This removes the amp guage from operation, powers the accessorys
fromthe yellow wire which has a fuseable link already in it for protection.

Mike D. (Have done nither of the above, but have been thinking about it for awhile)

[chrism]

If you have a Delco alt now the one one from a '91 waggy will bolt right up and plug in.
Please see the post above about wiring if you have an amp meter though.

[Peter Matusov]

Heimeken,

I've grabbed a largest (physically) Delco alternator at a junk yard I could find, believe it is a 105 or 120A model. Cost me $35 (junk is expensive in SoCal). The rebuild kit was something like $15, consisting of new voltage regulator, brushes, and bearing. Took about 20 min to rebuild it. Maybe 10 minutes extra trying to sort out all the washers and spacers so that the pulleys lined up perfectly.

it is a bit scary to see the ammeter needle to peg 60A immediately upon the start-up; the ammeter really has to go. But the power's there right off the idle with the original pulley, unlike most high-amp alternator kits.

Peter

[Nobby]

Originally posted by Stolen76:
IF you don't have an ammeter you could just drop it in. I'd run a new charging cable to the battery or starer solenoid. Use 8 gauge or 6 gauge wire, but bypass the ammeter.8 gauge on a 100 amp alternator is riding the edge.
Use at least 6 gauge. Using larger cable can only do you good. 8 gauge is really only good up to somewhere around 80 amps. Sure you probably will never make a full 100, or 80 come to that but you never know. A good rule of thumb is to go one size larger anyway. If you go via the starter solonoid make sure the wire from the solonoid to the battery is large enough too.

[MrWagoneer]

whilst on this subject, allow me to intrude with a question about the ammeter...mine has a -60 to +60 amp range, i got the impression it represented the charge going to the battery (it never seems to stray far from zero), rather than the current delivered by the battery to the entire electrical system (in which case i would expect to come close to +/-60 mark scale whilst starting or operating the tail gate electric window ect).

could someone pls clarify the ammeter purpose?
and possibly indicate what current rating my stock alternator is ('75 wagoneer, factory 401).

note: when i pulled my dash out, i noticed the heavy gauge red and yellow wires going to the ammeter, the red wires' insulation was badly melted, i completely covered it with heat shrink to avoid shorts...no current elec probs though.

[ December 04, 2002, 08:07 PM: Message edited by: MrWagoneer ]

[Heimeken]

There's a 100 amp alt. on ebay for $40, I've also seen them new(summit I think). Every time I turn on my Off-road lights everything else goes dim. Even with just the heater on at night things get dim. My '85 has the ammeter so sounds like I'd have to bypass it. Could I possible swap a new Gauge cluster? I think I have one from an '89.

I'd like that explanation MrWagoneer mentioned above too. My ammeter neve goes beyond +-30.

[Nobby]

Mr Wagoneer
The ammeter is there to show if you are charging or discharging the battery.
-ve = Discharge
+ve = Charge

With a good battery and alternator on a stock load setup, you should normally only see positive figures. If your alternator fails the needle will go negative.
Add on more and more electrical loads and the needle will start to drop towards zero. Enough of a load I.e more than your alternator output and you'll go negative.

Not sure what your stock alternator is I'd guess its somewhere around 60-70 amps though.

If you've got melted wires then check out for good connections etc, also make sure the alternator is not a replacement that is now oversized for the stock wiring. See this current running thread

http://www.ifsja.org/ubb/ultimatebb.php?ubb=get_topic;f=2;t=014964

[Nobby]

For starters I do not have an ammeter on mine however I have never really found factory supplied ammeters to be that accurate, also just because it goes up to 60 does not necessarily mean you'll ever see it. My speedo says whatever it is, i forget 100mph perhaps, never done that though.(In my Jeep that is)
That doesnt really answer your question though.
It really is simple maths. You have various items using different current loads.
For example 60W headlights= 2 at 5 amps
Radio say 3 amps
Heater fan no idea lets say 15 amps
If you run these items with the engine off the meter should show 0-5-5-3-15= -28 Amps You are discharging the battery.
Now If you start the engine up and lets assume for a secound that you do not charge the battery but the Alternator supplys current for this load the needle will go Zero. The battery is not giving but it isn't recieving either.
Now Say you have an alternator that is rated at 50 amps maximum output and its a perfect world and you are now charging the battery just after starting up as well as having all these loads on then the meter will show 50-28= +22 Amps. Thats assuming of course the battery wants 22 Amps to charge. It will only take what it needs to charge up but it will take what it can get if it needs it. A flat battery will accept 100's of amps if you can supply it does'nt do the average battery much good however, i digress though.
The alternator is able to carry that -28 amp load and still give 22 Amps to charge the battery which will be a positive you are charging the battery.
So why on a normal day after driving for a while with no loads on do you see a small positive number. Or more to the point initially the +ve number is +20 amps or so and slowly drops to say +8 Amps. This is because you were charging the battery initially at a higher rate due to it being discharged from cranking the starter motor. As the battery reaches full charge its current requirement reduces so the needle drops accordingly.
Now at this 8 amp charge rate turn on a 5 amp load. The needle goes to 3 amps? No it will momentarily drop until the alternator kicks in and supplys the 5 amps to carry that load and hence the needle should rise back to the charge current the battery was asking for 8 amps.
Jeez its getting late time for bed.
The figures I have given are not necessarily realistic but to give an example.
Also it is not a perfect world so a 50 amp alternator may well not give a full 50 amps, depending on engine RPM and how hot it is etc.
Does that answer your question well for a stock situation and a well maintained battery with an engine that starts easy and no lazy starter motor battery drain on startup will be minimal so the charge current will not be excessive you wont go really any higher than +30 amps. Alternator not producing any output the max electrical load you can create probably not much more than -30.
Anyone reading this and find a mistake go easy on me its way past my bedtime! smile.gif
Toodle Pip.

[MrWagoneer]

thanks for the informative response Nobby, and the link as well,

No shunt; the battery is charged through about twelve feet of 10ga wire that the Ammeter sits in the middle of, reading the charge directly.

Often the ammeter itself begins to fail, melting itself and the red charging wire to it as well.
goodness me, that certainly broadens my horizons !

[MrWagoneer]

i posted while you were typing up your second response :]

boy...after that performance, you really deserve your sleeptime :]

great discussion ! you have clarified in much more detail. once again , thankyou.

[mdill]

Totaly agree, in "normal" operation on a stock FSJ the Amp guage should never see
more than about 30 amps for any lenght of time.
The problems start mainly from "Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley happens" lights get left on, batterys fail (had one that
was a ***** in that the plates would short together intermitantly take out the fueable link
and then check out OK by debug time), regulators fail ... it is under these conditions where
the system should fail gracfully (NO MELT DOWN) and I beleive the stock system will do
just fine. But start doing some backyard engineering i.e. let's just stick a bigger alt in the
the hole, changing the size of the battery ... (some can take a lot more charge for a
longer time than what stock unit could) can upset the balance of the system, it may operate
just fine under "normal" conditions for years but is just waiting for the Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley happens event
to push it into melt down. Make changes if needed ,but think of the total system and figure
out what happens when "Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley happens".

Mike D.

[Bob Barry]

What usually happens is that the ammeter itself fails. It measures whatever amps are not sucked up by the vehicle itself (lights, accessories, ignition, etc). The red wire off the back of the alternator goes to what is affectionately known as the "big splice", a duct-tape-wrapped junction of all (+) feeds drawing power from the alternator. This sits between the alternator and the ammeter.

Whatever electrical energy isn't used by those accessories (virtually everything electrical on the truck) makes its way through the ammeter back to the battery to charge it. The sensor wire that tells the voltage regulator inside the alternator how everything is charging is in that circuit is between the ammeter and the battery. If it senses voltage falling below a certain point, it boosts the output of the alternator so that it can power the truck AND keep the battery charged.

What *seems* to happen in the ammeter failures is that the resistance in the ammeter itself increases, either over time or all of a sudden. The sensing wire is seeing less voltage (in addition to powering the accessories, the ammeter is also doing its best imitation of a toaster, converting electrical energy to heat energy), so the regulator boosts the output of the alternator. This in turn causes the ammeter and the red wire to it to heat up even more, which increases the resistance, which causes the voltage regulator to see less voltage, which causes the regulator to boost the alternator output, which causes everything to heat up even MORE...

You get the picture. It's a vicious cycle, and it continues until the ammeter completely burns out, the wire to it melts and shorts to something, causing it to break the connection, or the dash wiring catches fire, and you bail out of the truck, less concerned about seeing where this circus-act is heading than with saving your life.

This all happens with the stock 61A alternator. A 100A alternator would just make the truck's final immolation all that much more dramatic.

The easiest solution is to do the 2-stud to 1-stud wiring change on the back of the ammeter. The better solution is to run an additional heavy-gauge charging wire from the alternator to the battery. I think the best solution is to move all high-load circuits (lights, tailgate, etc) out from under the dash and run them through 40A relays with short runs of wire near the output of the alternator.

[Lindel]

Very good idea, Bob! I likes!! :D

[Peter Matusov]

Bob,

the voltage regulator in the alternator is integral, there's no sensing wire.

the stock ammeter in the jeep measures all the current between alternator and battery; if your accessories are connected to the battery, it will read "charge" when the accessories are on. Basically, the accessories are powered by the battery, and the ammeter reads the current alternator provides to top the battery off.

If your lights and such are connected to the alternator side, it will read "discharge," but not a whole lot.

all in all, not a very sound setup. Mike Baxter came up with some explanation for this ingenuity, but I forgot it.

peter

[Nobby]

So are you saying that in stock configuration the tap off point for the vehicles electrical loads is on the battery side of the ammeter terminals. That makes no sense. If this is the case then the +/- ammeter is a waste of space. Really only needs to be a +ve meter.
I'm sorta finding that hard to believe.

Hey Bob nice explanation.
Im so glad I have a voltmeter and you can still judge charge rate loads etc O.K.. smile.gif
Factory install ammeters in my book are just fires waiting to happen. I just recently completely reharnessed an IH B180 truck because the owner had replaced the original Dynamo with an 80 Amp alt. Guess what that 10 gauge wire running all the way along the harness to the ammeter and back did! Somehow nothing caught fire though, I'm guessing it blew the regulator before it really got a chance to get going.

[Heimeken]

This is great guys. Great explanation Nobby. Sounds to me that for my problem a dual battery setup would prolly work better than going 100 amps. afterall, I know turn on my 99 accessories here and there os the batteries would be charged up.

[Nobby]

Heimeken, Haven't got time to right much now but if you install 2 battery system you will create issues.
For starters when both discharged your charge requirements will be higher. usually solved with a bigger alternator. Also too when both discharged you will probably get a higher output from your stock alternator, meaning you have to upgrade that wire going to the ammeter, better still get rid of the ammeter.
I would suggest if you stay on the stock alt. 2 batterys set up you upgrade the wiring and perhaps install a battery selector switch. So you can select either of both batteries. That way you have one battery as backup, or if one battery becomes inoperable you can switch it off so it doesn't harm the other battery. A dead battery in a paralell circuit will constantly bring down a good battery. You can also charge one battery at a time so as to not overload your stock alternator. REMEMBER do not turn a battery on or off during charging you will blow the alt. regulator. It is safe however on a selector switch to say go from one of the batts to both or vice versa, just not off! Conversly if you happen to fire up with both batterys off to not turn them on whilst running. Silly me how would you start the engine! You get my point though. You can get protectors to cure this problem but its just more money and wiring!
Whats even slicker is a higher output alt. upgraded wiring, 2 batterys, a charge isolator and a selector switch. That way you are always charging both batteries but can select how you wish to feed the loads. 1 2 or both.
This was supposed to be quick. smile.gif
I haven't covered everything just trying to show that a 2 battery setup is not always as simple as just paralelling in a 2nd battery.

[Bob Barry]

Originally posted by Nobby:
So are you saying that in stock configuration the tap off point for the vehicles electrical loads is on the battery side of the ammeter terminals. That makes no sense. No, the big splice is in the red wire between the alternator and the ammeter. The only thing in the yellow wire between the ammeter and the battery is a lead that splits off and goes to the alternator.

Peter, you describe a one-wire setup, which wouldn't be stock on an ammeter-equipped FSJ. There is that lead from the yellow wire that goes to the plug on the alternator.

[Nobby]

Peter, you describe a one-wire setup, which wouldn't be stock on an ammeter-equipped FSJ. There is that lead from the yellow wire that goes to the plug on the alternator.[/QB][/QUOTE]

Thanks Bob as I suspected.

[crazyguy]

hmmm, now I wanna go disconect the ammeter and pull all its wiring out.

[2ndtimearround]

How about a 200 Amp alternator and it is made in the U.S?

Check out Mean Green Alternators and Starters:

http://www.mean-green.com/

I have their starter in the YJ. It is amazing. It is made of solid blocks of aluminum and it has a 4-1 reduction grear drive.

The Alternator is going to be a Christmas present (again for the YJ). They are not cheap but the quality is excellent.

For dual battery systems check out Wangler NW Power Products:
http://www.wranglernw.com/

Lawrence