Alternater not keeping up???Possible?

Need some opinions.Is it possible that this Powermaster alternator cant keep up with the power being used.Electic fan,electric waterpump,electric fuel pump.Volt meter shows 12 with ignition in the on position and 13 to 14 with the engine running and everything on.Did a test on the battery with the engine running at 1500 rpm and it showed around 15.I can charge the battery and it will be fine at 1st but it seems like it gradually drains it.Go to crank it over the next time and will need a charge again.No numbers on it but i think 75 amp alternator.

Volts might be good, but you need to do an AMP draw test w/all accesories running. AMP's are the important part to look at when using multiple eceltronic peices( ignition, cooling, fuel, etc.... ) and 75A is kinda on the small side with all that stuff .....

How many amps is the alternator putting out at idle.

I had a similar issue, first part of my issue was the fact I changed the pullies out to some performance pullies, once swapped my car stops charging when at idle. The issue I had with my battery crapping out was the fact the bolt that connects to the brake pedal that make the brake lights come on was loose, and when I turned the car off my brake lights stayed on killing my battery.

good luck

Ran the car some more with battery fully charged.Volt guage started out at 13 and after some driving it is gradually dropping,seems the higher the rpm the more it drops.What should the output amps be at idle?Do you check it at the battery or alt.?

Output depends on demand. Take it to an electric shop and have the system tested. You may have a couple things going on from a bad cable, poor conections, bad cell in the battery, etc. If evetything checks out a larger alternator is in order.

Is there a mopar alternator with the 1 wire hookup larger than 75 amps?If not and you purists are gonna cringe a little,i will put a gm one on it.

Find a shop that has a vat machine. They will be able to do a load test on the complete system and on the battery by it self. The battery load test has to be done on a fully charged battery though to be effective.

wannadrag summit sells one wire alts that are mopar style mounting 100amp for around $130

Take the battery down to Autozone, etc and have them test it first. Just because it reads 13V with the engine running does not mean that it is good. If it does test out good, then start worrying about the alternator and other parts.

this is just a personal opinion but i wouldnt trust what autozone says for testing. where i live we have an autozone and an advance auto parts and i have more than once taken something to autozone to be told its good and then took the same item to advance to find out its bad for example i took an alt to autozone they said it was good because according to their tester it put out a charge i then took the same alt to advance who told me it was junk that it was only putting out 15 amps i also had a similar situation with a starter so i dont use autozone for my testing anymore and as far as the battery comment goes once the car is started the alt should power everything if you are loosing voltage as you drive then your problem is in the alt. not keeping up

Ran the car some more with battery fully charged.Volt guage started out at 13 and after some driving it is gradually dropping,seems the higher the rpm the more it drops.What should the output amps be at idle?Do you check it at the battery or alt.?

Should have 14.5 volts when running. While running pull your "positive" terminal and the car should stay running. If it stalls your not charging properly. Just check on your batt terminals with a volt meter for the 14.5 volts when running...

You can have volts, but not put out any significant amperage. I can read voltage at both ends, but if its broken down to one strand of wire left, you wont pass any amps. If you have an electrician or electronics buddy, you put a clamp-on DC ammeter/Amprobe on the alternator output wire. This could still be something as simple as a bad connection. Voltage = pressure, and it just dont take much to stop 12 volts! I'm not a Mopar expert [yet], but did they ever use fusible links in the alternator output wire? Some alts. dont start any serious current till 12-1500 rpm, so dont test at idle.

Has a 1 wire now and the wire from the alternater to the battery is new.Tried a different battery and still does it.

Changed out the alternater for a 100 amp unit and the charging issue is gone.

glad to hear its fixed out of curiousity who did you get the alt from, is still the one wire internally reg and how much did it cost you

Ok but the purists are gonna cringe a little.Delco 100 amp,Late 70s Buick Electra with a 403,These are a little different than the chevy ones as they mount similar to the mopar.Internal regulater but is not a 1 wire,need to run a hot wire to excite it from the switch.$97.00 Advance Auto Parts.

Do you have a picture of it mounted ?

No pics,but it is mounted low.Useing the lower mopar mount,but the alt is on the bottom side of it,then a C shaped slotted bracket bolted to the water pump housing for the adjustment.

So how did you wire it.

#8 wire to the battery from the alt bolt teminal and hook the 2 wires from the alt flat plug together and run it to the accesory terminal on the switch.Remember though this car has a aftermarket harness and was already set up for a internal regulated alt.I have used this type of gm alt on antique tractors as well as my streetrods and i wire them all this way and it works for me.

I had a similar issue with my Belvedere II... I spent hours trying to track down my issue.
Other symptoms I had... fuel gauge would read incorrect, and dash light issues... and the voltage gauge in the dash bouncing around at idle, and the voltage gauge would flucuate with the brake lights and blinkers being used.
Oh and the car would loose its charge in about 2 days if it remained in the garage.

It ended up being an issue with the voltage regulator... The regulator worked just enough to get some the accesories working however the reahstat (not sure how to spell it) but the arm inside the regulator was shorting across the ground causing voltage to leak from the battery... which also caused the gagues to read incorrectly. So if you have not replaced your voltage regulator from behind your dash cluster you should consider it.