Alternator options

[Kern Dog]

Hey guys,
I'm adding A/C to my Charger and the current alternator seems to struggle to produce 12 volts at idle. It is a 2 groove with a 2 3/4" pulley. It was a parts store rebuild from a few years ago. I don't have electric fans or a big stereo but the battery is in the trunk. I have a ground from the block to frame and battery to frame. The underhood harness is new. I would expect a stock alternator would be enough but unless this alternator is underperforming, I need something more.
A buddy likes to use the compact Toyota based alternators. Also, Some late 80s Mopars used a small unit, maybe made by Nippendenso? I'd need a 2 groove for use with the 2 groove A/C pump I'm going to use. I don't know if the Toyota and Mopar alternators were both made by Nippendenso or not.
I looked at a Flaming River alternator....Holeee CRAP...$650 for an alternator??
What did you guys do for improved output ?

 

[Kern Dog]

I started thinking....
The stock alternator for an 89 Diplomat was a smaller, non traditional type. I checked out Rock Auto...
https://www.rockauto.com/en/moreinfo.php?pk=37719&cc=1090909&jsn=440

This might work. 2 groove, external regulator and 90 amps. Maybe I'll buy one locally to check fitment. I may have to cut and modify the mounting brackets but no biggie...

 

[Yatzee]

Hey guys,
I'm adding A/C to my Charger and the current alternator seems to struggle to produce 12 volts at idle. It is a 2 groove with a 2 3/4" pulley. It was a parts store rebuild from a few years ago. I don't have electric fans or a big stereo but the battery is in the trunk. I have a ground from the block to frame and battery to frame. The underhood harness is new. I would expect a stock alternator would be enough but unless this alternator is underperforming, I need something more.
A buddy likes to use the compact Toyota based alternators. Also, Some late 80s Mopars used a small unit, maybe made by Nippendenso? I'd need a 2 groove for use with the 2 groove A/C pump I'm going to use. I don't know if the Toyota and Mopar alternators were both made by Nippendenso or not.
I looked at a Flaming River alternator....Holeee CRAP...$650 for an alternator??
What did you guys do for improved output ?

These are the best units I've ever hung on a Mopar as an upgrade. Go to your local "pick and pull" or auto recyclers and snag a small case unit for about $50. Or pay big bucks and buy the make-over models by Powermaster and other top line re-manufacturers. Just go on google and search: "Ford 3g alternator on a Mopar". And yes you can swap pulleys to go from serpentine to double groove v-belt. Have one slung low on the right side of a BB for five years with no issues.
Puts out a solid 14.2 volts at low rpm's regardless of how much is energized.

 

[Kern Dog]

That would help...14.2 volts! Right now it starts off below 10 if the cold start RPMs are not kept over 2000. Cruising at low speeds under 1500 rpms it isn't bad, running up to 13 volts. If I have the headlights on, sitting at a stoplight, brake lights too....it drops below 10 to around 8 volts. I have an aftermarket gauge cluster in the car with a voltmeter. Lately it seems to move like a tachometer!

 

[Nacho-RT74]

this is the one I'll get when money is enough

http://www.tuffstuffperformance.com...ry-cast-plus-8509dp.html?ref=category:1267434

here all the options

http://www.tuffstuffperformance.com/c-1267434-chrysler-alternators-1960-1988-oem-wiring.html

there are 130 amps, but I don't think that much is necesary... 100 amps alt should be on 55/60 amps rate at iddle. fairly enough

 

[Demonic]

There's low and then there's too low. Something is off on your alternator. If you have a good multimeter you could disassemble it and check all 6 diodes. Of course, then you'd have to decide if you want to go to the trouble of finding replacements, pressing them in, etc.

Or you could just replace it.

 

[Nacho-RT74]

on the cheap, stock replacement ( and kinda stockish look ) with good output... this is the boy!

https://www.rockauto.com/es/moreinfo.php?pk=4768590&cc=1090730&jsn=549

( search it by PN or Diplomat 85 78 amps alt )

these are couple of mm wider. Can fit a bit tight but trim a bit the rear spacer could do the job for easier fit. Longer belt will help too, because trimming the rear spacer will get the back of alternator closer untill maybe meet with block.

BTDT ( is the one I'm running at this moment, stock A/C and driver )

 

[not so famous bob]

These are the best units I've ever hung on a Mopar as an upgrade. Go to your local "pick and pull" or auto recyclers and snag a small case unit for about $50. Or pay big bucks and buy the make-over models by Powermaster and other top line re-manufacturers. Just go on google and search: "Ford 3g alternator on a Mopar". And yes you can swap pulleys to go from serpentine to double groove v-belt. Have one slung low on the right side of a BB for five years with no issues.
Puts out a solid 14.2 volts at low rpm's regardless of how much is energized.

Same position here. Sets where the fuel pump would normally be, under the motor plate. 130 amp 1 wire, charges at at low rpm.

 

[JimKueneman]

Few agree with me but in most cases (i.e. electric cooling fans....) there is little need to upgrade alternators. I still have my 1968 original 36A alternator on my Coronet that I rebuild. Factory AC, Fuel Injection with an electric fuel pump. The only time it hangs in about even (discharges a bit) is below 1000 RPM with the AC and headlight on. It is all in a quality battery and a good low impedance electrical connections.

 

[Billccm]

I agree with Jim. March issue of mopar action magazine had an article by Richard E saying the same thing. A 30 to 40 amp alternator is recommended for the old mopars. A higher current alternator puts more heat into the systems voltage drops.

 

[Nacho-RT74]

If you drive allways on higways above 1000 rmps, maybe a stock 35, 40, 50 amps could be fairly enough even with AC... but definitelly not in the city or any heavy traffic situation.

about the the old alt rates better for the old mopars... Bulls**t, no matter who says that. Of course needs to take care of every detail when doing an upgrade. You can't upgrade JUST the alternator... same than you can't highly upgrade your engine without take care of the convertor, or axle.

stop underestimate electricity

I'm wondering how many of you really drive daily your od Mops on todays traffic requirements and situations... and what about when it rains and you turn on your wipers! then a traffic light, let's say 9 pm.... I do ! ( well, did, when my car was in one piece LOL ) and with AC

is simply... you need to be able to get around 50 amps iddling IF NEEDED ( and trust me, sometimes is needed: wipers, A/C or heater since the blower is the sucker, headlights and brake lights ) to be safe and in peace. If more, even better. Your car will never suck more than needed no matter if you install a 200 amps alt or if is able to put 200 amps iddling

 

[JimKueneman]

If you drive allways on higways above 1000 rmps, maybe a stock 35, 40, 50 amps could be fairly enough even with AC... but definitelly not in the city or any heavy traffic situation.

about the the old alt rates better for the old mopars... Bulls**t, no matter who says that. Of course needs to take care of every detail when doing an upgrade. You can't upgrade JUST the alternator... same than you can't highly upgrade your engine without take care of the convertor, or axle.

stop underestimate electricity

I'm wondering how many of you really drive daily your od Mops on todays traffic requirements and situations... and what about when it rains and you turn on your wipers! then a traffic light, let's say 9 pm.... I do ! ( well, did, when my car was in one piece LOL ) and with AC

is simply... you need to be able to get around 50 amps iddling IF NEEDED ( and trust me, sometimes is needed: wipers, A/C or heater since the blower is the sucker, headlights and brake lights ) to be safe and in peace. If more, even better. Your car will never suck more than needed no matter if you install a 200 amps alt or if is able to put 200 amps iddling

I sort of agree with you, but the engineers from 50 years ago where not completely guessing in their designs. They understood all the accessories on their product and sized the alternator accordingly, for traffic patterns of the day. I do agree that todays traffic there is a lot more idling that does make a difference in how the original designers made choices. The unfortunate things is the way manufactures are selling these alternator upgrades is in a way that makes better sales brochures not what most people actually need. They could use modern techniques to make more efficient field windings and keep the overall output about the same with much better output at low RPM but they won't because that is no where near as sexy as touting a 200A alternator.....

Case in point:

1960's Externally regulated, 61amp, model 10DN, Delco alternator was 8 to 10amps@1500 RPM and at its max rating@2400 to 2500 RPM
1970's Internally regulated, 63amp, model 10SI, Delco alternator was 35 to 40amps@1500 RPM and at its max rating@1275 to 1325 RPM

The second would be perfectly fine for all but the few that have 30A cooling fans and 1000W thumper stereos but that data would not sell alternators.

 

[bearman]

Before any up grades to alt you should figure out what your amp load is and what it will be. This will give you answer what your going to need from your alt. Most of and in a few amps for the cycling system which in most cases will be your a/c clutch and cooling fans. Everytime one of these cycle it will spike your alt and your amp draw goes up just for a couple of seconds then it will mellow out at the new amp draw until you turn it off and will return to normal amp draw. I am making this harder then ot needs to be so cut to the truth if your system needs a 80 amps to run get a 80 - 90 and so on always have a few extras for add ons later.

 

[Nacho-RT74]

Oh well of course, I'd never buy an alt because is advertised as 200 amps, that's not a candy for me, but the guarantee on 60-65 amps iddling, just like buying a cam not due the max duration but the duration at .050º. I will never need 100 amps on my car LOL, just that the max output gives at leats a guess on the iddling output ( which uses to be around 55-65% of the max output ) Would be great the manufacturers really would post the output chart!

note I'm not toward to the 130 amps Tuffstuff alt, but the 100 amps.

I bought a Beck Arnley replacement 80 amps alt from Rockauto long time ago, and chart included on alt shown me 45-48 amps iddling at 2000 rpms ( alt rpms, not engine ), and even I wanted a bit more juice, well, it worked ( while it worked LOL, untill rotor failed )

 

[Kern Dog]

Today I ran the car in the garage/shop and once it was up to temp, the voltage was at 14-15 at idle. I turned on the headlights and it momentarily dropped to below 13, then went back to the 14 range. I pressed the brake pedal and it dropped to around 12 and stayed there. I'm surprised that the brake lights seemed to draw more power than the headlights. Regardless, the voltage output seemed okay as compared to how it was a few days ago. It increases nicely once I am over 1500-1600 rpms. Maybe I don't need a new alternator. The A/C crank pulley I'll be using is a 7 1/4" unit, the current NON A/C pulley is a 6 1/2". The larger pulley is about 11.5% bigger, making the alternator turn faster. That should help it at idle.

 

[Nacho-RT74]

there are two sizes of alt pulleys too... laters are the smaller ones making them spin faster

 

[Kern Dog]

I think that there were more than 2. I have one here with a pulley that looks to be about 4 inches! The smallest that I have seen is 2 5/8" or thereabouts.

 

[bearman]

I am thinking out loud but i believe that the larger one is fine with a stock engine with the smaller pulley your amp draw will maintain its self in traffic. This is only my thoughts. Maybe someone else can explain it better.

 

[Kern Dog]

I thought that the big pulley was probably from a high rpm engine, maybe a race engine or a Hemi....
Wow...That would be the only rare and valueable part I own!

 

[bearman]

Have you done the old trick with the positive cable yet? If not try and see if the engine stays running or dies. What you described to me it sounds like your alt is acting like a generator not an alt. If ot stays running put the cable back on then turn everything on including the heater take a volt reading at the big post and the little post. Then one by one start shutting down each draw to see which draws the most. again thinking out loud you may have a heavy draw because of a wrong ground or a heater motor going out etc. Didn't you also say the wiring under the hood was new ? And has the car always done this or is this just showed up after the rewire?.