Replacement Alternator AMP Max

[Tyron68]

Needing to replace my alternator (68 charger 440, added AC). The alternator that was on the car had part # 3874271 on back. What is the biggest amp alternator I can go with without upgrading wiring?

 

[ckessel]

Maybe the 78 amp unit that came on the K cars. Back in the late 80's/early 90"s, that was an upgrade suggested on Mopar Action. I put that on my 70 Challenger. Pulley was different though but thats an easy swap. Going more than that, it would be a good idea to upgrade the wiring.

 

[RJRENTON]

Needing to replace my alternator (68 charger 440, added AC). The alternator that was on the car had part # 3874271 on back. What is the biggest amp alternator I can go with without upgrading wiring?

Use the 46 amp alternator that came as standard equipment on A/C vehicles. Changing the drive sheave, requires a special pulling tool and the alternator must be disassembled to press on the drive sheave (using a press to put it on in the position for belt alignment) as it's an interference fit. DO NOT heat the sheave to put it back on. Refer to the FSM for proper method......just my opinion.....
BOB RENTON

 

[Nacho-RT74]

Maybe the 78 amp unit that came on the K cars. Back in the late 80's/early 90"s, that was an upgrade suggested on Mopar Action. I put that on my 70 Challenger. Pulley was different though but thats an easy swap. Going more than that, it would be a good idea to upgrade the wiring.

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This could be a good option on the cheap, which with the propper pulley size (the one used on 80s alts) will be able to source up to 45 amps at iddle. Very important load capacity to feed the A/C blower along with some other accessories. Still a bit short if raining and needing to turn on wipers with A/C on (depending on blower speed selected thought) at a traffic light on nights.

However, like mentioned I still would advice get AT LEAST one straight path between alt stud and ammeter withouth going throught the bulkhead. If you are keeping the factory one throught the bulkhead, add a 12 gauge extra path won’t hurt. Not a huge or hard to make upgrade, just add one wire. But still check the factory charging circuit conditions at bulkhead.

My Charger was a daily driver for long time into the tropic so A/C was a bit of mandatory and this alt made a huge difference on the car with accs response.

These alts are around couple of millimeters wider and fits a bit tighter. On my 74 400 at least I had to get a longer belts setup because the rear of the alt was meeting with the block, so a longer belt will sway the block. Also had to grind a bit the rear spacer for a better belt alignment ( more reason to get a longer belt setup).

For a 68 if still using single field alt, using this alt will need to ground one of the alt brushes.

 

[Tyron68]

Use the 46 amp alternator that came as standard equipment on A/C vehicles. Changing the drive sheave, requires a special pulling tool and the alternator must be disassembled to press on the drive sheave (using a press to put it on in the position for belt alignment) as it's an interference fit. DO NOT heat the sheave to put it back on. Refer to the FSM for proper method......just my opinion.....
BOB RENTON

Bob, why is replacing the drive sheave required?

 

[Tyron68]

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This could be a good option on the cheap, which with the propper pulley size (the one used on 80s alts) will be able to source up to 45 amps at iddle. Very important load capacity to feed the A/C blower along with some other accessories. Still a bit short if raining and needing to turn on wipers with A/C on (depending on blower speed selected thought) at a traffic light on nights.

However, like mentioned I still would advice get AT LEAST one straight path between alt stud and ammeter withouth going throught the bulkhead. If you are keeping the factory one throught the bulkhead, add a 12 gauge extra path won’t hurt. Not a huge or hard to make upgrade, just add one wire. But still check the factory charging circuit conditions at bulkhead.

My Charger was a daily driver for long time into the tropic so A/C was a bit of mandatory and this alt made a huge difference on the car with accs response.

These alts are around couple of millimeters wider and fits a bit tighter. On my 74 400 at least I had to get a longer belts setup because the rear of the alt was meeting with the block, so a longer belt will sway the block. Also had to grind a bit the rear spacer for a better belt alignment ( more reason to get a longer belt setup).

For a 68 if still using single field alt, using this alt will need to ground one of the alt brushes.

I am planning on doing the ammeter bypass at some point as that seems to be something a number of people on this forum are recommending. I did buy and install the headlight relay kit from crackback.

 

[Nacho-RT74]

No need to bypass the amm, just source correctly all the accesories… and I would check the ammeter itself, not just outside but inside disassembling it.

My Charger is (was untill I dissasembled for a deeper resto job) a REAL daily drive car with A/C with stock system including ammeter… with that 78 amps alt and everything sourced correctly. Including halogen headlights with relays system, trust me. The amm needle barely flicked.

Also installed relays for each one of the blower speeds.

Those amm bypass recomendations comes mostly from ppl who don’t understand or don’t want to understand how to make it to work propperly. Or are still affraid about it.

 

[RJRENTON]

Bob, why is replacing the drive sheave required?

Because if, you are going to use the 46 amp alternator from an A/C vehicle, a double belt arrangement was used. You did not state if you're using the Chrysler RV2 Ccompressor or rhe Sundun.....which may or may not use a double belt drive. I assumed the double groove sheave. In all regards, special tools and techniques are required remove/installed the sheaves on a Mopar alternator. Accurate information results in accurate suggestions to your query........
BOB RENTON

 

[Tyron68]

Because if, you are going to use the 46 amp alternator from an A/C vehicle, a double belt arrangement was used. You did not state if you're using the Chrysler RV2 Ccompressor or rhe Sundun.....which may or may not use a double belt drive. I assumed the double groove sheave. In all regards, special tools and techniques are required remove/installed the sheaves on a Mopar alternator. Accurate information results in accurate suggestions to your query........
BOB RENTON

Understand. My set-up is a single belt with vintage air kit.

 

[RJRENTON]

I am planning on doing the ammeter bypass at some point as that seems to be something a number of people on this forum are recommending. I did buy and install the headlight relay kit from crackback.

Why?? If you are NOT adding any additional accessories, you DO NOT need to change anything. The old expression "IF IT'S NOT BROKEN, IT DOESN’T NEED FIXING" applies, in spite of what "others" think, do,or say. The original ammeter circuit will work just fine, the headlight kit relay, does not need the ammeter bypassed to function, it receives the headlight power thru the relay kit directly from the battery not through the bulk head wiring, hence, no need to change anything, other than the relay kit's source...it actually removes the headlight power from the factory wiring....do not be goaded into listening to the uneducated as in #7 above. Just my opinion, of course....
BOB RENTON

 

[Nacho-RT74]

NOTHING, NOT EVEN RELAYS MUST BE SOURCED FROM BATTERY IN AMMETER EQUIPPED CARS!

Even CRACKEDBACK advices to feed its relay kit FROM ALT POST if ammeter is on the game still playing.

IF SOME LOAD IS SOURCED FROM BATT, AMMETER WILL BE GETTING THE SUCKED LOAD by ANY equippent added BEING READ AS A CHARGE (if alt is capable at certain speed) WITH AN UNNECESARY LOAD RUNNING … as far alt is capable… INCLUDING RELATED WIRES, being NOT a charge load, but sourcing. False reading and unnecessary load added throught the charging network.

If alt is not able at idle, then the false (or partially false) charge reading will be HIGHER when revving up the engine. Hence why upgrade/increase the alt output, aside source E V E R Y T H I N G from alt side.


DAMN! it seems now also 72RoadrunnerGtx is wrong now after your aproovement? (Like if was necessary)

And my own personal lived experience FOR YEARS ON A REAL DRIVER CAR and what MaMopar made along their fleet cars (from where I based my suggested mod) is false and worths nothing, right?…

$**T

I’ll give you an advice… TRY IT BEFORE JUDGE (throwing constantly disrespectful replies), then think about it.

(Oh!, maybe you don’t drive anymore these cars, being stucked still on the 70s)

The worst part of this is that WE ARE BOTH AGREED ON THE BYPASS AMM METHOD IS NOT NECESSARY.

 

[Nacho-RT74]

I HOPE THIS WILL BE CLEAR. And if not, @72RoadrunnerGTX please correct me, since it seems even when we support the same, somebody around still keep saying I'm allways wrong but you are right.

Load reading magnitude on each status can be different depending on alt capacity, headlights load request ( wattage and low or highs ) and engine speed. Readings represented are just referential. It could be a flickering on needle on every status.

Bulkhead schematic is 71/74 B Body based ( also E body )

 

[Nacho-RT74]

I must say also, with engine OFF, and headlights ON it could be a light discharge reading not due the headlights load really, but parking lights/cluster lights circuits which won't be really "relayed" from batt but being sourced from main splice ( alt side of ammeter ). But the load requested by the headlights won't be represented on ammeter ( except if some tiny load to trigger on the relays )

JUST LIKE WHEN CRANKING THE ENGINE, which load requested BY STARTER MOTOR is NOT on ammeter, due the side the load is being sucked out... straight from batt. Well it will happen the same with headlights relays being sourced from batt.

EXCEPT when is ilustratted.

UNNECESARY LOAD RUNNING THROUGHT THE AMMETER!!!!!!

 

[Nacho-RT74]

With ammeter playing, FEEDING ALL ACCESORIES OR UPGRADES CORRECTLY FROM ALT SIDE, WITH A CORRECT ALTERNATOR RATE ABLE TO FEED ALL THE LOADS WILL GET YOU RIGHT ON THIS:

( from Chrysler literature )

ONCE AGAIN WITH AN ALT ABLE TO FEED ALL REQUEST AT ANY SPEED, NOT JUST GIVING GAS... Iddle speed capacity has been since EVER the first weakness on Chrysler products... then the bulkhead, specially on alt path. Hence why the first or bigger burnt path it happens on alt side.

If Chrysler had equipped with higher ouput alts from factory, or alt able to source enough at iddle... STILL with packard terminals on bulkhead ( on a correct sourcing stage ), maybe 70% of cars with burnt paths was survived to the burnt process, because the constant batt charge load was being barelly present on them, and most of the time ammeter was offered a ZERO ( or close ) reading.

( also if ppl had sourced CORRECTLY added accs and upgrades along the years, never fom batt )

Zero reading means, no load running throught ( on any sense ) and no charge load on alt path at bulkhead either, but just car demand loads. Saving maybe 10 to 30% ( or even more depending on batt discharge status ) of the load running throught the bulkhead on alt path.

 

[Nacho-RT74]

On afew words:

what gives you a wrong Accs/HL relays added on batt side ?

With an alt barelly able to source the main splice demand?
A constant no load reading for accs on amm but a discharge status from batt without registering that ( 1st and 2nd note diagrams)... As soon you give gas, the last diagram stage, with more load that should be there, including both Charge paths at bulkhead.

With an alt able to give all the required power AT ANYSPEED ?
A constant but unreal "charge" reading ( 3rd note diagram )... once again unnecesary load running throught there. Including BOTH charge paths on bulkhead.


Now...source straight from alt post. The only load to feed any acc/HL relay running thought the system will be with engine off &/or an insuficcient alt. Then upgrade the alt able to source as much as posible AT ANYSPEED, and the load going throught will be present mostly just with engine off. Huge step up to get a calmed down charging system

 

[icetech]

NOTHING, NOT EVEN RELAYS MUST BE SOURCED FROM BATTERY IN AMMETER EQUIPPED CARS!

Even CRACKEDBACK advices to feed its relay kit FROM ALT POST if ammeter is on the game still playing.

Wow, i had never considered that.. and i 100% would have just went from the battery.

 

[Nacho-RT74]

now, getting back to the alt option, using a 80s 78 amps alt... here is a load chart of one of them I bought long time ago:

It came with the small diameter pulley ( double for A/C ).


This was maybe 20 years ago and the one I got satisfactorily running on my car with a decent ( not perfect yet but quite decent at least ) and better output for years. Halogen Headlights with relays ON ALT SIDE... and 4 added relays one for each A/C-Heater speed ALSO on alt side. 73/74 blower speed control switch plug tipically melts down due the poor contact inside the switch and the high load sucker the blower is, so installed relays. 6 relays in total inside the cab taking power from amm stud ON ALT SIDE once extra path added for it.

I did run a straight ADDED path between alt and amm stud, and all relays I installed are INSIDE the cab taking power from AMM STUD on alt side.

SUPRISE! NO HEAT ANYWHERE, and ammeter relaxed most of the time. REAL DRIVER CAR on a HEAVY TRANSIT CITY into the tropic

There are better options nowdays but they are on $200 rate and I will go for it sooner or later, while this lates stock replacement alt coud be on $80 ( less if giving core ). Back in the days I got it on $40 or so ( maybe $50? ), without core.

ON A SIDE NOTE:
I simply added an extra path because after rebuild my wiring system with new terminals and get a perfect conditions bulkhead, didn't want to modify it. So having a perfect bulkhead path, an extra parallel path is more than enough. Some ppl is tower to eliminate completelly the bulkhead path and use a thicker path out of the bulkhead. I don't think is necessary, except if your instalation is already burnt and you don't care about get it working back again like factory. Personal prefference.

Ammeter was furtherly checked adding some soldering lead inside between stud and shunt, and insulator sheets replaced. After 50 years of use/abuse, ammeter can be on any conditions inside

 

[Nacho-RT74]

Oh! And before any Degree speech AGAIN

The Captain of the Costa Concordia cruiser ship Captain Francesco Schettino got his degree also, but back in 2012 still:

 

[72RoadrunnerGTX]

On an all-factory original charging system, for it to work as designed, any added loads need to on the alternator side of the ammeter, as are all factory loads, nothing added directly at the battery, no exceptions. Load placement matters with this charging system. The alternator is the primary power source while the engine is running. Any loads at the battery will draw its current from the alternator and register as false charging current, rendering the ammeter useless in its function to monitor the actual charge/discharge status. As well, it places the entire charge circuit under unneeded additional current stress.

 

[icetech]

I am curious about something.. why do people want max amp alternators.. if a lower amp alt puts out enough to charge the battery and run the car/lights and all, what's the advantage to putting on a higher output one?