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??
I am not interested in the 1970s basketball sized alternator, thank you.
What did you guys do for improved output ?

Tough Stuff makes a bolt on stock looking replacement 100 Amp alternator that is black powder coated that works real well with no other changes to the wiring or anything else Bolt it on, hook it up and go
I bought and used one on my old pump gas street Duster that worked very well, even with two group 27 RV/Marine batteries mounted in the trunk

I'll check it out.
I checked Rock Auto using an 89 Diplomat search. They had 90, 100 and 120 amp alternators. The "Denso" came in 90 and 120 amp versions and were available with a 2 groove pulley.
Is there a problem with using a 120 amp alternator if the car wiring is in good condition??

I have the 120 amp alternator that used to be available from Mancini. I have newer harnesses in my car and various loads that you don't have such as fans. I put the a/c in my car and have had no problems so far. I will say that since I upgraded my battery doesn't drain down anymore, so my alternator was questionable anyway. I did the MAD electric modification to the car, that was also helpful as far as durability.

Powermaster also makes an upgraded stock unit. I have one in my duster and it works great.

I have been running this Powermaster unit for the last three years. My headlights are bright and no power issues at idle. They sell them in one or two groove pulleys.
It is a one wire and I have done all of the wiring upgrades before the install. I had to tweak the spacers a tad with the aluminum heads, but no big deal.

Thank you, Gentlemen...I have some shopping to do!

replied at FBBO

check the thread stickied at DC.com I wrotte

&/or:

http://www.heritech.org/cuda/Charge.html

Thank you!

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.

Check to make sure all of your grounds are good in the rear harness.

& the RPM was the same as the prior test?

(LN 100 amper...


Like the Cop cars usta' have...

The relay kit that Crackedback sells will make your day. I have a Powermaster on the GTS. Works great. Lights don’t dim while idling. I got the 60 amp alternator in natural finish, took it down to the parts store and had it bench tested. It was right on at 60 amps.

Well! Changing to the solid state voltage regulator on my '64Dog with its completely stock 37(?) amp alternator solved the lights dimming at idle problem.

Here are some truisms:

A 120 amp alternator with a decent voltage regulator puts out exactly the number of amps the system requires.

A 120 amp alternator will put out up to its rating if you load up the system.

Throwing 120 amps at a 37 amp system loaded more than its capacity WILL cause any weak spots to become obvious, as the magic smoke escapes into the air.

Having battery voltage drop, as an instantaneous load is applied, is normal. What you see as the voltage rises to the right number is what the voltage regulator is supposed to do. As it senses system voltage dropping, it increases the field current to increase alternator output.

Most of the loads hooked to the power circuit have an instantaneous inrush current which is two to three times the operating current.

Back in the day I bought a small round ammeter device that was held against the line in question and read out amps. I can not find it now.


R.

CORRECT



CORRECT



will mean the wiring and connections are underrated by the systems requirement, but not an alt fault. When the alt is not enough the batt will provide the lack of power from alt ( discharge reading ). So the load remains the same, just the source changes. And still will mean is underrated.

This becomes worst when the batt is discharged, which will add MORE LOAD to the system. THIS is the failure. We need to keep the batt out of the play becoming on a load sucker ( charge reading ) after being sucked out

so... if your car sucks average 25 amps at iddle and the alt just sources 18-20 amps while iddling, the rest of load ( 5-7 amps ) will be provided by the batt.

Once you rev up the engine, the batt becomes on part of the sucker system, so your car is NOT anymore a 25 amps sucker, but mostly sure the full alt output... 35 amps. But 10 amps takes QUITE LONG to get recharged the batt on the car. This is what gets stressed the system, coming and going.

conclusion... an alt able to feed everything at iddle, and reinforce the wiring up to ammeter... done. The car will keep sucking the same load, the batt won't suck anymore because won't be sucked anymore, and will ge an stable power system

AND NOTHING hooked to the batt, because this will be read by the ammeter as a charge, being not a charge

Lots of good comments... I'll just emphasize two. 1) With any upgraded alternator or even without its a good idea to beef the weak factory wiring in certain areas. Bypass the bulkhead connector with charge current in some fashion (many ways to do this) and upgrade charge wire size based on alternator you pick. A heavier charge wire is really important with single wire since the regulator cannot adjust for drops. 2) The upgraded squarebacks can make 100 amps or more running but idle output is not so hot (eg 50 amps). A newer style alternator and/or bigger case is needed to get good idle output.

Bigger drive pulleys, smaller alternator pulleys and higher belt speed can help at idle but no fun if high RPM damages the alternator or you throw a belt.

(Frankie...

Go find you a 100-amp LN...

Like the old Mopar Cop cars had...

OEM...

or a modern 100/120 amp nippondenso 3 wire from a dakota or minivan, etc. you can change out the serpentine for a v-belt pulley easy enough. and they work for a long, long time, so even a junkyard unit will work, and is cheaper to boot than a new one.

I looked at the newer ones used in the B vans. Both looked great but the mounting bosses/ style was almost vertical. The RB mounting has the top bolt at about 2:00 and the bottom about 8:00.
The positive terminal would touch the engine block in the one I saw.
I could certainly make a set of brackets if I decide to take it that far.
Thanks!

I’d take a look at tuff stuff alternators. I bought their 130 amp 3 wire square back, just like the original one. It has 65-70 idling amps. I’m running a BeCool dual fan set up, AC and so forth. Have all new factory wiring, I do not use the ammeter as I have Dakota gauges. I also ran a 8 gauge wire from the alternator to the battery as suggested by Nacho, he also said I could run it to the starter relay but I chose the battery. It absolutely works perfect. Here’s a Summit part # TFF-9509DP. Dual Pully just like you need. Those guys are up in Cleveland if you want to look them up and give em a call.

did it came with an output chart?

I'd like to know the 100 amps unit output at iddle. Per your 130 unit specs the 100 amps should be on 55-60 rate! That would be great for me!

I Called and asked them Nacho. I can give them a call tomorrow and ask them for you .

Hi,
I've been following this post with interest and emailed Tuff Stuff about the 130A alternator. Someone named Matt Oliver answered my email and told me that the alternator produces 65-70A at idle. Unfortunately no output curve even though I asked about it.
Hope this helps,
Martin

I have been running the stock Mopar alternator on our 73 440 Dart 9.5:1 since 2000. Never an issue with under charged battery and the alternator looks like it belong on a 440.

I use the Toyota Denso unit. AndyF make a nice bracket for a factory look.
Gus

That does look nice. I wonder if he had something to accommodate a 2 groove pulley in an A/C type application.

I looked, never could find anything. This linky was the best option I could come up with. Seems like 90 amps ought to be sufficient unless you've got some big power options installed?

Robert

I didn’t even ask about the curve but mine works great and they seem to have a lot of good reviews from summit. I’m glad somebody makes them in a factory square back, those GM/Toyota looking alternators just don’t look right on our Mopars.

In response to the Amp "curve", From what I have read, many seem to peak at or below 2000 rpms. I don't know if this is alternator RPM or crankshaft RPM.

^^^ with how overdriven the alts are I would assume crank RPM. but this ain't my area so I am strickly guessing/bored.

This is the power output chart on the 78 amps BeckArnley Alt I got from Rockauto several years ago. It says alternator RPMs I guess because is the only known pulley size, since is installed

Nacho - That is GREAT! I've not seen a fully graphed output for a Chrysler unit - and I've been looking. Lester # 7509 is a squareback, yes?

That is the shape of alternator outputs.
They are always in alternator/generator rpm, except the specs in the service manual. Service manual specs are for verification in the vehicle.

Lets look at the Beck Arnley test results. Really good struff in here.
RPM: Say the crank pulley is 6.5" and the Alt Pully is 2.625", then alternator wil be driven roughly 2.5 times faster than engine rpm.
Therefore idling at 600 rpm will = 1800 altenrator rpm.
& idling at 700 rpm (like with a A/C idle solenoid) will get 2100 rpm.
Big difference where it sits on that curve.

Output: "Output current tested at 13.20 volts" This is really important. 13.2 Volts is barely above battery float voltage, and maybe .4 volts above its real voltage. If the test was repeated with the same load, but voltage controlled to 14.5 volts, the current output would be lower. Most of the shop manual tests spec 1250 engine RPM, and 15 Volts. So to compare, the above test to factory specs we've been given, we need to do some math.

Turn On speed: Below this RPM the output is zero, zilch, zed. In the example using a pulley ratio of 2.5, that works out to 525 rpm.

Field current: This is what the rotor windings will draw at maximum demand, 7 Amps. That's 7 more amps from alternator to bulkhead to main splice, back through the bulkhead to the alternator field terminal, to regulator to ground. (Assuming later style voltage regulator). A good example of why having all connections in top shape is important. Of course if there's equipment to be drawing 81 amps, either there are bad connections, a dead battery being recharged, or a lot accessories... Nothing to really worry about unless there are electric fans or fuel pumps, etc.

The shop manuals I've looked at generally give field current draw for turning the alternator by hand! Something around 2+ amps at 12 Volts.

yep, is a late squareback alt with non visible stator iron, and using a diff brush isolator than earliers squarebacks, the one perpendiculat to the rotor shaft. Alt is a bit wider... It looks no more than a remanufactured Chrysler alt. Just last long a year and a half or so ( Rotor went bad ).

just like this, althought on the link says 60 amps, but well, you can read the chart on mine, spec’ed at 78 amps

https://www.ebay.com/itm/BBB-Industries-...TEAAOSwPgxVNFYw

This is the bottom of the chart card! I attached there the decals. You can read the PN. Just found bought at Clearly Auto not Rockauto ( found the return merchandise form ). I think paid something like $50-55 for it