New alternator and battery. On1978 corvette won't charge

Is the charge indicator light lit on the insturment cluster ? (battery symbol ) Did you check for B+ voltage on the bigger wire on the back of the alternator ? The S terminal in the connector should have B+ voltage ,as well as the F an L terminals . No battery voltage at any of these will cause it not to work . Do you know what a wiring diagram is ? Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. Year , make , model an engine . Under system click on engine ,then under subsystem click on charging system . Then click the search button , then on the blue link . This diagram show all connection's on the alternator . All wire's should have B+ voltage , testing with a volt meter . Could have blown fuse , fusible link etc...

You have an alternating problem..I assume on a 76 model you have an internal regulator...if you have no voltage meter then charge your battery and start the var then pull positive battery terminal...if car dies,alternator is bad and needs replacing.If it stays running your at least putting out some voltage but might not be enough...most parts stores(Auto Zone,ect)will do a free voltage check(on or off vehicle)

replace the alternator, its guilty as charged, no pun intended.

CHECK WIRING THIS UNIT WILL CONTORT THE FIELD IN THE COMPUTER. THE FIELD CONTROL IS WHAT MAKES IT CHARGE.

Hi,
There's a draw on the system. you'll need to have it diagnosed for electrical. Could be the alternator - bad diode in mine caused it to kill the battery.

There's a LOT of stuff on Vette's that could cause this.
GL,
Td

If battery was just replaced i would guess alternator. Find a local autozone and they will test it at no charge.

If both the alternator and the battery are good, either the alternator isn't turning fast enough (slipping belt or engine idle speed too slow), or you have a wiring problem.

To check your wiring, look for the "1" terminal on the back of the alternator (left side of spade terminal connector). When you turn the ignition key to the run position without starting the engine, the alternator warning light should be at full brightness. If the bulb is burned out, the alternator will not get the excitation current it needs to start up (it goes through the bulb). With the engine running, you should measure 12 Volts at the 1 terminal (this is the excitation terminal).

Another thing to check is whether the battery charge wire is good. If it is corroded inside at the battery clamp end or burned out, you won't get charging even though the alternator appears to be working. If you don't have an ohmmeter, you can make a quick test by adding a new 8 AWG wire between the output terminal and the battery clamp. If the battery now charges, the original wire is bad. If this works, I recommend installing an inline fuse at the alternator end no larger than the largest size used in your electrical system, just in case something happens to the jumper wire. That way you won't burn out your alternator.

The heater/AC issue could very likely be a separate problem, but inadequate power may keep that system from running properly. (Note: low idle speed or belt problems will also be detrimental to AC performance.)

This means that your alternator is not charging anymore and likely needs to be replaced. You may want to have the battery charged then checked as well. Sometimes a failing battery can cause the alternator to fail because they require a higher charging cycle that can prematurely burn out the alternator.

Yup, that won't be enough as it is normal battery voltage. You need 13.8 to 14.8 or so. Pull the alternator and get it bench tested. Alternators have diodes inside (one way valve for electricity, that converts alternating current to direct current, which your car is). and these diodes fail and leak. There is a set that turns on the regulator that fail..

All will have the same result. rebuild the alternator.

If it bench tests okay, be sure to guarantee good ground cuicuit.

Usually the regulator is built in to the alternator..........have the amps checked on the alternator the volts are not the only sign of charge