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.