When i start my 85 the battery only charges at 11 volts but after running for about 15-30 minutes it charges fine. im going to go get the battery and alternator test tomorrow, was just wondering what else it might be. thanks

 

have the alt and battery tested.

Check connections to alt. On the back side of the alt. there is one connection that is held on with nut that I think goes to the battery. Be sure that the connector is large enough for the wire. Too small of a connector will play havoc with the charging system. Check to be sure battery cable connections are clean and tight.

 

If You rev up your Corvettes engine up to 2,000 RPM's, Does the Dash Voltmeter read at least 12.6 V ?

Nomally it should read around 13.2 - 14.4 Vdc.

If the Alternator does not sustain a voltage level of at least 12.6Vdc output, then the cars electrical system usage draws from the battery alone. The alternator cant keep up with the vehicles electrical demand.

Be a good idea to load test the battery in Corvette.

A Sun Vat 40, Snap On battery load tester, or an Autometer battery load tester all work great for testing.

If You have a Fluke style DVM or even a Radio Shack multimeter that can read DC voltage,

take a reading off off the back of the alternator charging post ( heavy 6guage RED wire).

Take the reading at engine idle(600-800 RPM's).

Then Rev up the engine up to 2,000 RPM's.

Should have around 13.2 - 14.4 Vdc.

Underdrive crankshaft pulleys a previous owner might have installed will cause a low charging condition at low engine idle speeds.

Have an underdrive crankshaft pulley on my 87.

Doesnt put out much at engine idle. At 2,000 RPm's I have 14.4vdc.

Underdrive pulley was installed by the previous owner of my Corvette.

BR