alternator question

[archie307]

hey i was wondoring what voltage my alternator is supposed to be putting out.before the regulator it puts out 14.9 after the regulator its about 12.8-13.5 max. usual is about 12.9. it just doesn't seem to be keeping up and sometimes my battery dies after driving and mostly at night when my lights and heater are on. It has a new battery and starter.

[VetteVet]

Start Here and then post back with more details. Year of truck, alternator amps, internal or external regulator, Where you took your readings etc. I suspect your alternator is too small amperage for the loads you are putting on it.

http://www.madelectrical.com/electrical-tech.shtml

[archie307]

its 72' gmc with a 78 chevy 350 in it. It has a external regulator. I took the readings from the main big wire coming from alternator going to the voltage regulator. took at that connection.got about 14.9. And on the other bolt connection on the regulator going towards the battery i get about 12.8. also took a reading at the battery it also says about 12.8. while the truck is running. When the truck is off i get 12.4. I don't know what the amps are the alt is. I don't look like a factory regulator. i'll take a pic of it tommorow when its light out if that helps. the alt has tabs like this --.

[truckdude239]

man threw that thing away and follow this http://67-72chevytrucks.com/vboard/s...d.php?t=119379 best 40 bux i ever spent i got mine off an 83 chevy k-10 with 350 took less then 30 mins total and it works alot better then the old stuff my light dont even flicker anymore.

[usernamessuck]

That old boy at mad electric knows his stuff. He is also very helpful over the phone.

[VetteVet]

The readings are as they should be but the alternator appears to be internally regulated. I would put as much load as i could on the system and see what the readings are at the battery. You know, lights, heater, fan, wipers and see what readings you get. just off idle they should be above 12 volts unless the alternator output is below 55 amps. There should be a stamping on the front frame of the alternator just behind the adjustment bolt
mount that says what the amps are. An externally regulated alternator has II for the plug and it's located on the rear of the alternator to the right of the bearing cap. I have included a couple of pics of an internal alternator and an external regulator.

[JimKshortstep4x4]

Upgrading to the internal regulated alternators is a good option but the factory style regulators are easily adjustable.

The output to the battery voltage should be 14.2 to 14.6 volts.

Jim

[truckdude239]

makesure that they didn't install the new inertal reg alt and not disable the old reg ont he core support

[ChevyC102007]

After I had the Old altenator and battery stole out of my truck my friend and I installed a internally regulated alternator. Truck was wired or appeared to be already wired for one but it still had the two extra wires for the guage and something else. After he installed it and wired it up it wouldnt start when I went down to get the truck after I got home from work. Turned out the ignition and the rest was wired through the old regulator on the core support, once that was hooked back up and the rest was done it fired up. The SI alternator still charges the battery at between 14.3-14.6 volts at 1000 rpm. Theres a second jumper wire over to the battery from a ballast or junction block on the fender...........can I disconnect the old regulator and the truck still start?

[archie307]

think i got it figured out.it is an internally regulated alt and someone wired through another regulator. thanks for the help guys!

[truckdude239]

just cut the 2 outside wires and put them together should chagre then