Alternator Capacity for 1968 Dodge Dart 270/SL-6

[mydart270]

another quick question pls....

(a) what is the capacity of the OEM alternator for my 1968 Dodge Dart 270 SL-6??. P/N is 2642537 per Chrysler Parts Catalog

(b) I replaced the above alternator w/ a 60A re-manufactured unit. Now when I start the car the AMP meter pegs to the RIGHT and slowly returns to the "middle". Battery voltage is 13.8 vdc and w/ lights ON, points in the middle (Good). Voltage regulator is the newer solid state type, well grounded to chassis.

Don't like the immediate "peg". I guess the starter motor is causing this. Lots of amps initially for start of engine, then, back to normal. Weird I think.

Any idea why I am experiencing this? Does not happen w/ OEM alternator.

Great forum, great people, great MOPARs...thx again

 

[halifaxhops]

Actually sounds about what it should be doing replacing the amps used in the battery when starting. Usually the OEM alts are 43 amps I believe so maybe the 60A is just replacing it faster then settling down? That's my GUESS!

 

[rumblefish360]

That’s exactly what is happening. The immediate punch in power is coming in heavy for that short time. If you had the 40 amp Alternator in there, the Amp gauge would not rise as high and fast nor settle down as quick.

 

[MoparLeo]

Catalog
Improved Wiring for older Mopars

 

[Mattax]

(a) what is the capacity of the OEM alternator for my 1968 Dodge Dart 270 SL-6??. P/N is 2642537 per Chrysler Parts Catalog

You ask tricky question.
2642 537 is a 37 amp alternator with single groove pulley.
37 amp is Chrysler's rating. It's probably the maximum or close to maximum output at a standard voltage. There doesn't seem to be an industry standard so its up to the manufacturer how they want to rate them.
Output goes up with rpm. Change pulley diameter or run a little faster and maxium output goes up quickly from idle, where its very low, especially on the older alternators.
Chrysler's service test, done on the car, shows the standard (37 amp) alternator must produce 23 to 29 amps at 15 Volts, (measured at the the alternator) with the engine held at 1250 rpm and using a carbon pile for load and voltage reg.

(b) I replaced the above alternator w/ a 60A re-manufactured unit. Now when I start the car the AMP meter pegs to the RIGHT and slowly returns to the "middle". Battery voltage is 13.8 vdc and w/ lights ON, points in the middle (Good). Voltage regulator is the newer solid state type, well grounded to chassis.

Ammeter going right is what it should do after start. This shows current is flowing into the battery. Your ammeter may be labled C for Charge on the right. (different years and models are labeled different).
Once the battery is recharged, the meter returns to center - showing no current flowing to or from the battery.

Don't like the immediate "peg". I guess the starter motor is causing this. Lots of amps initially for start of engine, then, back to normal. Weird I think.

If it pegs. First try recharging the battery on a charger. The battery charge may be a lower than normal and so its drawing more current.
Voltage at 13.8 measured at the battery must be with the engine running. That's a little on the low side but within the specs (13.5 to 14.5 V at 70* F)
If bringing the rpm up a little increases voltage when the headlights are on, then its telling us the alternator is barely producing enough power to run the ignition and headlights at idle. Typical with the standard 37 amp alternator, more so if there's some oxidation in the connections.
However, probably worth checking for resistance (seen as voltage drops) before blaming the alternator.

Any idea why I am experiencing this? Does not happen w/ OEM alternator.

Above guesses are as good as mine. Even if the new alternator has much much better output at idle due to pulley or design, pegging isn't right. Mid range - like 20 amos would be the most normally should see after a start. Usually its more like 10 amps. So possibilities are the battery is not holding a great charge, battery is just really low in charge, resistance somewhere between the ammeter and the battery. I've seen this (pegging) a few times recently as well - using the Standard 'studaker' VR. recharging on a charger (this battery has seen some abuse) seems to have resolved it. Time will tell.

 

[Mattax]

here's a remanufacturer's test print out that NachoRT74 posted on moparts.
Its was the box with a late 'square back' alternator.
Notice how the output goes up with rpm. (that's probably alternator rpm shown).
These are amps at 13.2 Volts.

and FWIW here's a Dodge truck FSM specs, probably late 70s or early 80s

 

[toolmanmike]

Output goes up with rpm. Change pulley diameter or run a little faster and maxium output goes up quickly from idle, where its very low, especially on the older alternators.

Huh, I don't think there has been a discussion about that. Should be easy enough. Wish the pulleys were bolt on though.

 

[67Dart273]

You guys can print all the specs and whatever you want but this is exactly the alternator's job.......to produce 14V. If the battery is "lame" or the starter draws 'a bunch' or cranks "awhile" then the ammeter will be "to the right" further and for a longer time.

THE BIG THING with your nice big 60A alternator is the lame old wiring in these girls. Bear in mind THEY WERE ALWAYS LAME and have GOTTEN WORSE with time.

"Ma" knew this and on cars with 65A optional alternators, MODIFIED THE FACTORY WIRING to improve the situation. Look it up!!! It's right in the shop manuals!!! It's called "fleet/ taxi/ police" wiring. It involved adding another wire through the bulkhead through a separate grommet so the bulkhead connector is not overloaded.

 

[67Dart273]

On an unrelated note, I once had a Mopar SB in a beater FJ-40 Landcruiser. Part of the time I had one of the "big frame" 105+ amp alternators on it, with a S&W 100A ammeter. The charge wiring (I forget) was either no8 or no6 wire. After a cold (winter) start or using the winch, that alternator WOULD PEG that 100A ammeter!!!! Some of my friends would loooooook at that and then turn and loooook at me like "whut??"

 

[halifaxhops]

Any one need the stock specks throw me a message I will scan and send them to you from the sun cards.

 

[Mattax]

Sequence of pretty normal recharging immediately after start.
This is with a later squareback, a standard roundback probably would be a less current in the first minute, and take a little longer to recharge.
Batteries general do better recharging at lower rates, especially AGM's.

Engine idling around 1000 rpm.

Its worth mentioning here - The ammeter is labeled 'Alternator' but it only shows current to and from the battery. Its not the alternator output.