Alternator slow charge

[Moparbuster]

My as alternator doesn't charge at low rpm let car idle 10 mins runs battery down 69 rr .40 over 11to 1 440 msd 6al new alternator and electric voltage regulator pain in my as

 

[Garngie]

So just clarifying: alternator charges at higher RPM, but not at lower RPM? Or you're getting no charge at all? Also, how many amps is the alternator rated at?

Any other details on the voltage regulator? Certain Mopar voltage regulators require single field alternators to work properly, while others require a dual field setup. I'm assuming you're using the electronic voltage regulator from Mopars 1970 and up (which uses a dual field setup) ?

It is most likely that either the alternator and/or voltage regulator is faulty. If you are positive they are both in working order, then there must be a loose wire or poor ground somewhere else. Check that your field terminals have good contact and no wires are suspect.

 

[Nacho-RT74]

Stock alternators are usually known as a low capacity charge at iddle, hence the reason why along the years charge bulkhead terminals get burnt ( due the high load recharge process when giving throttle PLUS the car power request ). so a good alternator capacity at iddle is VERY important to keep the car demand satisfied for stable power without need for a recharge demand from the batt after get sucked by the car due the alternator incapacity to feed it

HOWEVER there are some limits when you can say the alt is not even getting the low juice level still at iddle. I'd say the most tipical could be a rectifier diode saying goodbye to his life

 

[Moparbuster]

It charges good when rpms are above idle

 

[Nacho-RT74]

it well worths to check bulkhead conditions at black 12 gauge wire ( alt-amm wire )

 

[Moparbuster]

Somebody send me pics or tell me how they have their vr and alt. Wired up please just got back home from hot lap round neighborhood let it idle for 10 mins after got back battery is dead I have electronic vr with 2 field alt

 

[Nacho-RT74]

once again, check the bulkhead conditions for melted areas on black wire location coming from alt.

 

[RJRENTON]

As I've mentioned previously, IF the alternator's output (voltage AND current or amps) is low at lower or idle RPMs, suspect a bad diode (open). Early Mopar alternators, either the round or the square back design, use a three phase full wave bridge rectifier circuit, where an open diode, be it a positive or negative diode, will result in the alternator's capacity being reduced by half as this results in a single phase condition. IF a low voltage condition exists, the voltage regulator will try and compensate by driving the FIELD voltage to max, but because of an open diode, the unit cannot produce higher output. Under light electrical loads and higher than idle RPM's the alternator MAY produce adequate voltage AND current.....but higher loads will not be possible. The alternator's maximum output (current or amps) is design limited by the impedance (AC resistance) of the STATOR windings and the diodes used. BTW....the square back alternator's negative diode assembly are prone to diode failures. It is rare, but possible, for a rotor winding or stator winding to fail. The most common reason for low output is: diode failure or bad brushes or defective voltage regulator. Be aware of a possible bulkhead connector issue, but it is likely that this is not the problem. Load test the alternator in the car, using FSM procedures to prove the cause.
BOB RENTON