ken'svette

OK, I have been searching/reading/attempting to fix this issue for 4 months. I have replaced the alternator with a new French made one that matches my car. I have also replaced the ignition switch. I have checked the voltage coming off the alternator and it is in the 14 volt range. I also checked the amp drain on the battery when the car as fully asleep. All that is in order. There are no codes new or history on the DIC. I have checked for a voltage drop between the alternator and starter. Nothing is showing up wrong. The only symptoms are low voltage on the dash (11v to 12.8v) and DIC and dying batteries (2 new in last 4 months). Lately, I have been keeping a tender on the battery so I will know it will starts. This all started in the spring when I put on headers, replaced my starter and got a tune. I double checked the grounding lugs that I removed during the header install and replaced the starter because I damaged it installing the header. So in other words alot was going on this spring. I noticed the voltage issue after I had trouble starting the car at lunch time in April after the header install and tune. Replaced the battery and alternator after they tested bad. Went through 4 rebuilt alternators that all threw multiple codes before I found a new french built one. This alternator seems to work, no codes and puts out mid 14 volts when running. So after all that and thinking the voltage could be low due to a dirty ignition switch, I replaced it. No change in the volt gage. I also checked my driver door connections. I cleaned and checked all the female connections per the forum directions. I do have a charging system fault that appears very rarely on the DIC at startup. (that has happened since 2007) Any thoughts out there??? The thing that gets me is there are no current codes and no recurring history codes. Background, it is a six speed 2002 that I have owned since 2007. I have cleaned all the grounds in the engine compartment and I checked the grounding lugs near the headers. Sorry for being long winded....

DaDuck

I went thru 2 new Red Top batteries before I got a good one.

Swap your battery into a different vehicle and see if the problem stays with your vette or leaves with the battery.

It is a PITA to solve this type of problem.

dgrant3830

There is a fuseable link from the alternator to the starter where the power all ties together. If you are measuring power with a DVM, measure across the battery with the ignition off and see what the level is. Needs to be a minimum of 12.5vdc. Do a resistance check from the alternator to the positive battery connection. You should see zero ohms or like 0.1ohms. When the car is running, put your meter across the battery in VDC mode and measure therefore not counting on the DIC display and see what you really have there. Bill Curlee has a picture of and pointed out before that down low, between the battery and fuse box, there's a ground on the frame there. This is the ground for lots of the displayed references...I think. Bill, Lucky or 8VETTE7 will have the schematics whereas I don't. When you changed the starter, headers or whatever, did you losen the battery negative cable where it bolts to the block of the engine and insure its re-tightened?

edobernig

In an C-4 85' there is a relay for the 4 individual power amps on the Bose system that failed in my car located behind the passenger side dash. When I shut off the car the amplifiers remained energized. I couldn't tell why the battery was discharging but I could hear a slight "pop" when I turn on the Bose radio. Problem was a bad amplifier relay.

ken'svette

Poking around and saw lower voltage to the battery then was being sent by the alternator (larger then normal). Seems the starter has a loose post. It wiggles in the solinoid. Battery voltage and gage voltage goes up after wiggling it. Wow so that's it. now I have to loosen the header and remove the cables and tighten the post if possible or replace solinoid. Fun job!

dgrant3830

Do NOT forget to disconnect the negative battery cable at the battery before working down there!!!

Na4now

Do a "big three" on it.

I have bit of a low voltage issue, and thats the first thing Im trying, before I even test the alternator. I might add a couple other grounds, just for good measure. My factory grounds look small, and rusty.