Alternator gauge and volt meter gauge question

[potze426]

I have a 1963 Plymouth with a 440 engine. The other day the engine stopped running. come to find out the battrie went completely dead. I put a loaner battrie in and it started the car back up. Here is my problem, While going down the road doing 50 mph at 2000 rpm, the alternator needle is going rapidly fast back and forth from discharge to charge, and also the volt meter is running at 15 amps. 1500 miles ago I installed a new rebuilt alternator. The alternator gauge acted the same way even though the alternator was new. Please help.

 

[khryslerkid]

Sounds like the voltage regulator. Check all of your connections and grounds. Check that your voltage regulator has a good ground. Remove from the firewall and clean the surfaces where they make contact. You need bare metal there, at least at one of the bolt holes

And I'm thinking you ment voltage instead of amps on your volt meter.

 

[potze426]

Yes, I did mean voltage. I will check the voltage regulator for the ground situation. Thank you so much for your reply.

 

[potze426]

OK after removing the voltage regulator, I removed the paint on the bolt hole surfaces. This made a big difference. The alternator gauge needle shivers a little towards the charging side, and the voltage meter go's back and forth to 14.2 to 15. what do you think? Thanks again.

 

[Nacho-RT74]

do you have some accesory being sourced from batt ?

the normal reading after get a fully charged batt should be 0 as most as posible

 

[440 Charger]

I have a 1963 Plymouth with a 440 engine. The other day the engine stopped running. come to find out the battrie went completely dead. I put a loaner battrie in and it started the car back up. Here is my problem, While going down the road doing 50 mph at 2000 rpm, the alternator needle is going rapidly fast back and forth from discharge to charge, and also the volt meter is running at 15 amps. 1500 miles ago I installed a new rebuilt alternator. The alternator gauge acted the same way even though the alternator was new. Please help.

Sounds like voltage regulator.

 

[potze426]

Nacho-RT74 The only thing I can think of would be the MSD electronic ignition. Other than that I can't think of anything else drawing juice from the battrie. Also not sure what you mean by a fully charged battrie should be at 0. 440 Charger thinks it may be the voltage regulator. I believe I installed a transistor voltage regulator when restoring the car. Thanks to both of you for taking the time. Tom.

 

[Nacho-RT74]

The ammeter reads the load flow coming and going from/to the batt not really all the load the car is using, so, with a fully charged batt it won't demand to be charged, so ammeter it should be at 0 reading as far alternator is able to provide all the juice the car requires. The power is spreaded out from alt side, on a main splice down the dash harness tape between alt and amm, so the ammeter doesn't read that except if the batt is demanded to source that splice because engine is off or alt is not enough to source the car requirements ( will give you discharge reading on that instant ).

Of course any device being sourced from batt post ( or starter relay stud ) will be read by the ammeter as a Charge reading with a good alt sourcing, because there will be load going to feed that device throught the ammeter, but actually not the batt itself being charged.


The MSD ignition module doesn't suck really a lot of current, so it could be quite logic you will have allways a slight charge reading sourcing actually the MSD box... maybe couple of amperes. Needle could be just barelly passing the center line of the reading or a bit "off set" from center.

 

[451Mopar]

The old mechanical regulators pulse the alternator, but if voltage is still on the high side, make sure all the grounding is good. Battery to engine AND body, and regulator to body (or jumper a ground wire direct from regulator to battery ground.)
Also, double check alternator output voltage, and the voltage at the regulator. Ideal, they should be the same, but the regulator (ignition circuit will be just a tad less.) If the regulator hot wire into the regulator is less than the alternator (by more than 0.1 volt) , check the Ignition wiring for resistance / bad terminal connections.
Depending on the gauges, I have actually seen a voltage gauge, SpeedHut brand (Has digital inner workings), read higher than the actual voltage when it had a bad ground.

 

[potze426]

Thanks NatchoRT74 and 451Mopar. I have some homework to do. And thanks B bodies for this Site.

 

[Nacho-RT74]

Originally for a correct amm reading the MSD ignition module should be conected somewhere between ammeter and alt as ANY OTHER DEVICE ON CAR with all ammeter equipped cars, not really to the batt, HOWEVER I know what MSD instructions says about conect it to the batt.

anyway, while batt is getting recharged, the ammeter will stay on Charge side area and will be slowly going down to the center untill get it fully charged, then amm should be around 0 area. This could get you also on high voltage rate reading on initial recharge process.

If you turn on lights ( for example ) voltage could get slightly lowered and charge reading reduced at a steady RPMs, because part of the power the alt is able to source to recharge the batt won't go anymore to the batt but to feed the headlights, which is sourced from alt side of the ammeter.