Alternator Help

[69.roadrunner]

I think my alternator is bad but dont want to buy a new one till i'm sure i have tried everything. My volt gauge shows discharge at 10 volts. Put a meter on the Batt and its good at 12.2
- started the car and revved to 2Krpm and did not see any increase in volts to the batt. I think it should jump to 13 -13.5 volts.
-All connections are tight
-I am running a 75 amp dual pully powermaster alternator with an internal regulator on a 440 4 barrel pretty much stock engine. Alt Its only 2 yrs old
- I raced the car approx 15-20 times (1/4 mile) over the last 2 yrs . Could it have burned something out?

Thanks for any guidance
Steve

 

[sleepar]

Test the post on the alt wit the meter and it will tell you what's it putting out those powermasters have a internal regulator and should have 14.7 volts or close to it. Racing shouldn't hurt it any... with the car running and you remove the positive post off the battery and the car dies it is the alternator or its regulator...

 

[69.roadrunner]

Thank you! I will try it this week.

 

[69.roadrunner]

Car died the second I removed the pos post. Thanks for the advice. Time for an alt. can alternators / regulator burn out after 2 years of limited use?

 

[nm9stheham]

Sorry that you got bad advice.....and sorry to say that. But you NEVER remove the battery from a car's electrical system while it is running. If the alternator is not working at all, it should do not harm, but if the alternator is working, even partially, disconnecting the battery often will take the alternator out. The battery performs an additional function in the electrical system called 'ballast', which smooths out any large spikes as the regulator changes the alternator's voltage out in response to varying load. Without the ballast function, the voltage will usually spike widlly, and will take out an alternator, and often anything like an MSD ignition.

If the alternator is good, it should put out about 13.7 to 14.3 volts at fast idle. 12.2v on the battery means it is about half discharged or a bit more, so your diagnosis that the alternator is bad, or at least not working, is right. Check the voltage at the large terminal on the alternator with the car not runing and the key off, and the voltage should be almost identical to the battery's voltage.

Fuly charge the battery overnight so that it reads 12.6 or 12.7 v after a few hours of 'rest'. Then see if the alternator will work before you replace it. It is a long shot....

 

[69.roadrunner]

i did charge the batt and the charge held at 12.4. Started the car and at 2k rpm batt was at 12. let the car sit then restarted it again, At 2k rpm the batt charge dropped to 11.9. So bottom line...a steady decline.

I appreciate your reply. I will try the alternator posts just for craps and giggles, but i ordered a new alt tonight. Hopefully, that will do it.

Steve

 

[nm9stheham]

Yes, no alternator function for sure. BTW, your voltages are a bit low...it may be your meter. If you want to check it out, get a brand new 9V transistor radio battery and use that for checking your meter's accuracy. They will be 9.6 to 9.7 volts new out of the package.

If your meter turns out to be accurate, then I suspect either your battery was not fully charged or it has at least 1 weak cell. The 12.6 to 12.7 volts for a healthy, fully charged battery is a consistent number.

 

[sleepar]

Test the post on the alt wit the meter and it will tell you what's it putting out those powermasters have a internal regulator and should have 14.7 volts or close to it. Racing shouldn't hurt it any... with the car running and you remove the positive post off the battery and the car dies it is the alternator or its regulator...

I don't know.... but I have always done it this way.... the car should run with out the battery....

 

[nm9stheham]

^^^ Forsooth.... you are either lucky.... or lucky!

 

[383man]

Sorry that you got bad advice.....and sorry to say that. But you NEVER remove the battery from a car's electrical system while it is running. If the alternator is not working at all, it should do not harm, but if the alternator is working, even partially, disconnecting the battery often will take the alternator out. The battery performs an additional function in the electrical system called 'ballast', which smooths out any large spikes as the regulator changes the alternator's voltage out in response to varying load. Without the ballast function, the voltage will usually spike widlly, and will take out an alternator, and often anything like an MSD ignition.

If the alternator is good, it should put out about 13.7 to 14.3 volts at fast idle. 12.2v on the battery means it is about half discharged or a bit more, so your diagnosis that the alternator is bad, or at least not working, is right. Check the voltage at the large terminal on the alternator with the car not runing and the key off, and the voltage should be almost identical to the battery's voltage.

Fuly charge the battery overnight so that it reads 12.6 or 12.7 v after a few hours of 'rest'. Then see if the alternator will work before you replace it. It is a long shot....

I was going to tell you the same thing as its not good to pull the battery cable off with the car running. Have we tetermined what year this car is and what system it has on it ? It it the older single field alt or the newer dual field alt with the electronic regulator ? Ron

 

[Photon440]

I don't know.... but I have always done it this way.... the car should run with out the battery....

In the 'olden days' this was acceptable practice, if the car had a generator. Once the alternator was introduced on the 1960 Valiant the rules changed due to the delicate ac/dc rectifier diodes. You could get lucky, but more often you'll blow something. Sometimes you'll burn out only one diode, causing a flickering at idle and reduced charging.

 

[nm9stheham]

I assmue that since the OP said it was a Powermaster, then it is a 1-wire alternator...no external regulator or field connections.

And BTW when disconnecting a battery from a running car, sometimes it will blow the regulator, not the alternator; depends on the car.

 

[jz61]

went for a ride last nite, amp meter discharging, looked under hood heavy gauge wire from back of alternater is off,has a ringeye connector on it, looking to see where it should be connected, any help would be great, its a 65 Plymouth, I believe a 1wire alternator the terminal that plugs onto back od alternator has one wire

 

[jz61]

found it! seems output stud had rusted off, was able to re-connect!

 

[jimt1971rr]

When I lost my alternator, I just took it to the parts store and had them test it before I bought a new one. Yes, it was bad. I had never heard of pulling the post off of the battery while the car was running to check an alternator until very recently when my neighbor was selling his 02 Tundra w/ a dead battery and the buyer did that. I am surprised it didn't blow the entire computer!

 

[nm9stheham]

Good to hear ti was so easy. If your alternator has one large wire and one smaller wire on a spade terminal, then it is a standard Mopar alternator of that year.