i got a 76 and i just got a new alternator about a month ago (i drove my car about 8 times after that) my old alternator craped out, the new alternator is a 70AMP alternator so basicly i started the car yesterday and trund on the sterio and the the subs didnt hit at all. So i looked at my battery meater and it was at 0, so i grab a multimeter and test the battery it shows 12.3 abviouly the alternator wasent working. So okay i truned the car off tested the battery again and the alternator then started the car up again. To my suprize it started to show 14.5 so i was thinking maybe im stupid and didnt chek it right.
so for the hell of it i drove around town with a multimeter hooked up to the battery and i noticed that the more i drive it the more the voltage goes down from 14.5 to almost 13.6 even if im not using the sterio all though if i turn the sterio way up it basicly goes down to almost 13v. and most of the time when i just start up the car the alternator dosnt start to work right away. :confused:

 

If your car has an Alt/Gen/Bat red light on the dash....when you turn on the key to run position, does it stay lit??? engine not running??? does it go out when you start engine, and rev it a bit??

chance the old lightbult is burnt out....symptoms are what you describe....

in that 2 prong regulator circuit...you have a 12 volts source direct from system, this is your primary sense wire, then the other one goes through the 12 switch source through a lightbult to the other wire...so if key is off only ONE OF the reg wires has 12 volts on it....its the MOST clockwise position viewed from the rear....the one that is LEAST closkwise viewed from rear is the one in series with lightbult...and is switched too boot....both have full system voltage on them when car is running...same as output stud of alternator unless currents are high from large useage...heater, fans, stereo loud...etc......believe it or not, both of those regulator inputs are necessary to be wired correctly, OR you have to rev the engine a lot to get it to charge...burnt out bulb...or rev it a whole bunch, talking 3-4 grand in order to get it to charge...sometimes even if it's a famous 'one wire' regulator....

GENE

 

hey man i dono what you told me, it confused the heck out of me. The alternator on my vette has a internal regulator and its got no light only the (-40)-0-(+40) Guage. But thanks for the advice maybe i should have been more specific but anothe things is that reving the engine \ dosent change the voltage after its warmed up, only when its just started :banghead:

P.S. every time i see your vette i got to say its damn nice.... :thumbs:

 

There is a red "GEN" light on the right side of the center cluster, thats what he is talking about. If that light is burnt out the alternator doesn't work quite right.

 

The amprage will fluctuate on the dash gauge depending on the load at the time. some of the internal regulator alternators need to be excited by reving the engine a tad after startup. Once you rev it a bit it pops into action and continues working from that point on. The voltage readings you describe wouldnt nessisarly alarm me. Voltage readings can fluctuate depending on load also. Sounds right to me.