I have an '89 with 28k origional on it that is experiencing a problem I hope someone can help me with. About 4 months ago symptoms indicated that the origional alt needed replacement, which I did. Everything was fine until about a week ago when the car started running funny. A quick check of the guages and I could see the voltage around 9.0 or so. The battery was less than a year old but a buddy of mine was SURE that was the problem so I replaced it with another brand new battery. Voltage started out around 12.5 and after driving maybe 5 miles was back down to 9 or so. Called another buddy at a local Corvette repair shop. He was SURE it was the cheap reman alt from Auto Zone that I put on the car so I swapped it for another one right out of the box. I noticed when taking off the 1st reman that the large red bolted on wire lead had gotten quite hot, not enough to damage the insulation on the wire but had left a melted like impression on the grommet where the connector bolts to the back of the alt. After putting on the 2nd new (reman) alt and charging the battery I drove the car last night. The voltage reading through the dash guage started out at approx 12.5 slowly working down to 11.8 fluctuating the entire time. The battery light came on so I turned around to head back to the house and all of a sudden the light goes out and the voltage quickly climbs to 13.5. I turned back around and proceeded on with everything fine for about 10 miles then same thing again. I cut the car off after reaching my destination and she sat for a couple of hours. After restarting, battery light on, voltage droping I headed home. Voltage droped from approx 12.0 to 11.3 or so and about a mile from the house the battery light went out and the voltage quickly climbed back to 13.5. Sometimes when the voltage is acting up the anti-lock brake light will blink or come on momentarilly also. Please help, Dave

 

Dave it sounds like you have a loose connection. Anytime an electrical connection is loose there is resistance, and where there is resistance there is heat build up. The first thing I would do is to take the "bolted" lead off from the back of the alternator, and using an ohm meter check the continuity from that point directly to the battery positive post. It should be <5 ohms in resistance. That lead is connected directly to the battery positive terminal most likely via the battery cable connection at the starter.

Also visually check the connection at that cable to the alternator. If its charred from heat the connector eyelet maybe bad. Get another eyelet of the appropriate size, cut the wire back, crimp and solder the eyelet to the cable.

You may even have a connection problem at the battery post. What is the condition of them? Check for any corrosion behind the terminals, them side mount cables were notorious for corrosion under the bolt.