I'm out of ideas here. Here's my testing method. Negative cable off. Test light connected to neg cable and probe on the neg post of the battery. Light is on. I pulled every fuse including the flasher and light is still on. Disconnect alternator. Light is on. Disconnect ignition switch. Light is on. Un hooked the voltage regulator and horn relay and the light is still on. Take the positive cable off the starter and the light goes out, but if I touch the cable to anything metal, exhaust, frame, etc. the light comes back on. I had a slow crank issue and installed a new starter which fixed the cranking issue but the power drain was present before a changed starters. I'm running and HEI distributor. Today I decided to unplug the harnesses at the fire wall, separate them, engine and lamp harness and plug them back in separately thinking it would tell me which harness carries the component that is the problem. When I unplugged the harness at the firewall the light goes out, which I expected. I can plug each harness back in independently and the light won't come on. Snap them back together and plug them in and on comes the light. I have replaced the positive cable but not the negative yet. What am I missing here?

 

did you take one fuse out a time to narrow it down

 

Yes, I did. The light was still on with all the fuses out.

 

disconnect the alt wiring

 

Take the wiper motor out and see if it goes away. 68s are notorious (and the is a tech advisory in the AIM ) for the wiper override switch being left on which will engage the wiper park solenoid and will kill the car overnight. I also tracked a bad draw to a bulb. It was enough to slowly kill the battery but not enough to light the bulb. Try pulling the courtesy bulbs while watching your amp draw. It drew a current even with the doors closed.

While you are killing yourself to find this draw, install a battery disconnect and get in the habit of using it

 

The alternator wiring is good, it could be a bad voltage regulator, going to solid state or elimnating it is a good idea but you need a small harness change to switch to an internally regulated alternator, which is a good chance to go to a 100 amp or larger, but needs a larger charge wire run to the starter

 

LS5,

I will assume you jammed a stick in the door jamb to keep the dome light off during all the testing.

It will be helpful if you had a rough idea how many ohms your parasitic draw is.
A clock or a spare tire carrier light, hood light would be super low draw.
Whereas something more serious would be . . . . . . ????

Perhaps a trip to Harbor Freight for a cheap Ohm Meter.

Some of parasites over the yrs were:
Power antenna.
After market stereo.
Faulty alarm system (a second horn in the back)
Wiper relay.
Faulty door jamb switch.
Spare tire courtesy lamp.
Under hood light.
Under hood alarm.

Good luck

 

Well, I've been trying to figure this out for a couple of weeks and I start a thread and I think I have found the problem. I went out to get a hard number on an amperage draw and when I probed the cable and battery something would click behind the dash. I already had it apart to unhook the ignition switch so I unplugged a wiper solenoid attached to the back of the tach. The draw went from .875 to .400. So I grabbed the assembly manual and realized that although I had unplugged the 3-way flat connector from the wiper motor months ago, there was another 3-way connector behind the distributor. I unplugged it and no more draw. When I first got the car running this spring, when I hooked up the battery the wipers were on. I shut them off and I could never get them to work again. I guess that should have been a clue.

 

I hear ya.

On our daily drivers, it's common to accidently leave the automatic wiper sensor on all the time, even when parked unattended for several days. No harm / no foul.
I heard our old C3 electronics sometimes don't like that.

Not that I drive in the rain, but I always try to keep the wiper switch off all the time.

 

so the wiper motor was bad?

 

No, its not bad, thats normal with the wiper override switch in the wrong position.
Also the center glove box in the 3 rear compartments has a courtest light that doesnt always shut off. I have removed the bulb for that as well...always a good idea

 

So after all this, it was a simple turn of a ****? I wasn't aware of the lamp in the center compartment. I'll check that out and see if there is a bulb in there. The courtesy lamp/ lighter fuse was blown when I started pulling fuses. Thanks for all the help and info.

 

There is quite a bit of 68 only parts that are actually 66-67 parts. Your front spindles are 67, steering box is 67, radiators are swappable on big blocks, which you should do reagardless...the small block manual transmission version radiator is way to small for any decent hp motor. There are multiple threads on 68 only parts.

 

1970LS-5
Just a reminder. You do NOT want to interrupt the 1968 wiper cycle once it starts. Let them park on their own. OTHERWISE you could end up with an energized wiper solenoid drawing quite a good parasitic draw.....whether the key ON or OFF.....

See here: https://www.corvetteforum.com/forums...post1607052246

 

Thanks again for all the great information. This group is always very helpful when I've posted a question and I appreciate that.

 

I gave up on searching parasitic drains on my 68 and have a battery cutoff switch installed. I also keep it on a CTEK charger.

 

On my 73 convertible, my garage door opener light was burned out, and with the top down walking beside the car, I noticed the center glove box light was ON (even with the door closed). The OEM bulb was replaced with an LED and that’s probably the reason why my car always started.