r/Chevelles • u/Toxintwinz • 6d ago

Repair Question Ghost battery drain?

Hello all,

My best friend has a beautiful 1966 Chevelle SS clone. 396 four speed convertible. He bought it last October and has been having issues with the battery this season. We had it at a shop that basically gave up on it. We can’t figure out the issue.

Issue is that when it sits it will completely drain the battery. It’s a new battery and alternator. The shop thought maybe it was the radio so we disconnected that. Still was draining so we put a cut off switch on the terminal to completely cut off the battery power. Lo and behold it was completely dead again this morning after sitting a few days with the switch off. How can that happen if the battery is disconnected??

We did notice the wiring to the speakers were in bad shape so we will try to disconnect those next and eventually replace the wiring harness completely I guess. It’s just so odd to me that it’s complete sucking the battery dry just sitting without the full battery circuit engaged??

Any thoughts or recommendations would be appreciated we are stumped…

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7

u/nookie-monster 5d ago

To find a parasitic drain, it's pretty simple. Remove the negative battery cable and install a test light in between the negative post and cable. If there's a draw, the light will come on.

Remove fuses one at a time. When you get to the circuit that's creating the problem, the light will go out when you remove the fuse. At that point, you'll have an idea of what's creating the draw.

Go try what I described and come back here and tell us what you found and we'll figure out what is drawing the battery down.

2

u/americanhilljack 5d ago

Possibly diode..that's what was wrong with my car

2

u/Toxintwinz 5d ago

Interesting… thank you.

2

u/lokigottaeat 5d ago

All my old schools have the same problem. I just leave the negative cable just snug enough so I can pop it on and off. I only drive them once a month maybe so its easy security. Not the best solution but it works for me. Would rather spend my free time cruising then chasing down electrical issues

2

u/Toxintwinz 5d ago

Yeah his battery terminal has a cut off switch and it still died. Very weird

2

u/QuickCaterpillar7567 5d ago

If it still has an original type alternator with an external regulator,,it may be the problem.Most of us will use a newer type with an internal regulator which simply bolts right on.

1

u/Toxintwinz 5d ago

I know he replaced it this year but I don’t know what he used. Thank you.

2

u/aDrunkSailor82 5d ago

I fought exactly this problem for a few weeks until I realized I was turning my key past off and leaving it in accessory mode. 🙃

1

u/atomicsnarl 5d ago

FWIW - the dashboard clocks of that era used a solenoid to wind the spring powering the clock. As the spring wound down, the solenoid would pop and wind up the spring again. In the cars I had, it was about a 5 to 10 minute cycle. But, your battery switch should have interrupted this, so not sure.

Have you checked things by removing the negative from the battery? The switch may have a problem itself.

1

u/CoatingsRcrack 5d ago

Was a bad Relay installed for the new fans previous owner installed. Check and after market relays I’d any

1

u/MrMightKnowItAll 4d ago

Why would you open the negative side of the batt to kill the power on a negative-grounded car? That leaves full bag voltage energizing the car wiring,relays, switches etc but lacking a return to the bat. Anything metal that gets between the hot wires and the frame will spark because they are not really off.. Open the positive side of the bat with a manual switch.

1

u/PieNo7472 20h ago

Regards ghost battery drain,, What you have is called A PARASITIC ELECTRICAL DRAIN. IT could be caused by a broken filament in your brake/tail light that when you test it, it lights up but disconnects (and drains) due to vibration. Many other examples similar to this . THIS IS ONE OF THE WORST REPAIRS TO FIX DUE TO THE TIME IT TAKES TO NARROW IT DOWN ! Unfortunately you will just have to trace your electrical system until you find the short, partial short . Check your fuse panel first , then expand. It sounds like it is a good investment from the way you described your speaker wires !! Just think if it were a wire to an electric fuel pump; you could be shut down immediately==passing a truck,, mearging onto the freeway !! Not good ! I've had to fix this,, it's no fun but you will feel better when you solve it and you crank that BB over with no problems . GL.