[Claugemire]

Hey guys, I've been going through a bit of trouble with my Nova. It's a 74 nova 4 door with a 350. It's mostly stock with only a few simple upgrades. I was wondering if any of you fine people have heard of common circuits that develop parasitic draws. I've been trying to track it down without luck. My battery keeps draining all the way when it sits for more that 6 hours even after fully charging it. I've removed the radio fuse (which is the circuit I've tinkered with) and it still has the draw.

 

[brian oneil]

Usually if you have a draw, it is a ground issue somewhere.

 

[Big Dave]

You will have to isolate every circuit in the car starting with the battery. Charge it up and measure the voltage , Disconect the batterry from the car (both cables positive and negative). Check it daily for three days. The voltage shouldn't drop below 12.4 volts. If it does the problem is an internal short in the battery (usually caused bu charging a dead battery at too fast of a rate causing the lead sulfide particles to be shed off of the plates, that fall to the bottom and create a short).

Big Dave

 

[Youngladd]

Charge the battery, unhook the cable from the positive side of the battery, put a test light in-between the positive side of the battery and the cable. Once the test light is lit, start unplugging fuses one by one until the test light goes out. Thats the circuit you need to look at and find the problem. When the light goes out as you work on that circuit, you've cured the problem. :yes:

 

[Claugemire]

You guys are Awesome!! Thanks. My auto parts place has kept my battery over night to charge it for me, so that'll tell me if the battery is shorting internally (Thanks Big Dave!). I am going to replace all the main grounding wires because I really suspect they are all bad or getting there (Thanks Brian!). If this doesn't work I'll start with your process of isolating circuits, Youngladd.
Woot!:hurray:

 

[Big Dave]

If your motor has ever been pulled odds are that the grounding wires where left off by the shade tree mechanic that did it (first because they are hard to get to, and second they don't make sense if you don't understand electric circuits.

You can buy replacement cables from reproduction houses. Basically you are grounding the frame to the motor with one the body to the motor with another and the under dash wiring to the motor with a third.

https://www.summitracing.com/int/parts/gmk-4010-276-62s/overview/

You need to refer to your assembly manual to see where each end of the cable goes.

The second biggest problem with these old cars is paint. People love a shinny paint job on their motor but that is not how they where painted at the factory. The motor was fully assembled before it was painted, not a bare block painted first. If you look at these old Life magazine photos you can see over spray on everything:

By painting the block you electrically isolate the motor from a good ground. There should be no paint between the stater motor and the engine block, between the bell housing and the block or the motor mount and the block.

Big Dave

 

[Claugemire]

Wow Big Dave, those pics are amazing. In the first one it looks like a bunch of 409's! (I could be wrong).

I can't tell you how much I appreciate explaining the engine grounding. I never knew the body was grounded separately from the frame! I haven't done an engine swap yet (same tired smog era 350), so the ground should be hooked up right (not saying they're good, just still in place). I did a tranny swap with a painted tranny, but the bell housing was clean of paint and the crossmember SHOULD have a good ground to the frame (no paint in the crossmember mounting bolts.

Thanks again for the awesome pics!

 

[Custom Jim]

I'm not understanding this but how can a poor ground or no ground drain a battery down ?

Jim

 

[Custom Jim]

Be aware too that what Youngladd stated will only work on circuits that you are able to unplug the fuses.
There are factory circuits that do not have unpluggable fuses on them such as the horn relay, headlight switch, ignition switch, fuse block, and the alternator. These are on fusible links and they are in different locations on the vehicle.

Jim

 

[Big Dave]

I'm not understanding this but how can a poor ground or no ground drain a battery down ?

Jim

It can not.

A draw down of the battery is a circuit that is active or shorting out. I mention grounds because when you go to measure voltage in all of the circuits (I use a multimeter not a test light) it will affect your reading if there is a pained surface between the ground and the return path of the steel body. Actually the meter I use now is this product:

https://www.amazon.com/dp/B00AR4RCXW/_encoding=UTF8?coliid=I1OKGP7UKEWCE1&colid=11N30MEJ01XJH&psc=0

Whose design I see has been copied and reproduced at one third the price to be undersold by competitors:

https://www.amazon.com/dp/B00NPY02EW/ref=dp_cerb_2

Basically this is a volt meter that uses the car battery to energize the circuit with radio frequency pulses that the meter can detect if it shorts out emitting a noise. It can similarly find an open circuit where the end of the wire that is open becoming an antenna. By powering the circuit through the meter you can leave everything alone and just test what is in the car by sticking the probe through the plastic insulation to touch the copper core of the wire.

It has other functions to test sending units for car computers as well as gauges. Makes diagnostics a lot easier.

Big Dave

 

[Custom Jim]

It can not.

A draw down of the battery is a circuit that is active or shorting out. I mention grounds because when you go to measure voltage in all of the circuits (I use a multimeter not a test light) it will affect your reading if there is a pained surface between the ground and the return path of the steel body.

Big Dave

I know it would not and I was wondering what Brian said as maybe I had never come across that situation.

I know myself, helping others, that using a standard two wire meter across the vehicles battery posts and then moving those two connection points to a new spot will give you different readings but I think most assume it's a difference on the power side while in reality it could be that, or an issue with the ground, or a little from both sides.

Jim

 

[Claugemire]

Sorry for not giving an update in a while. I've got a real head scratcher now. I replaced the negative battery cable (that helped the ignition a lot!), but my volt meter still reads 0.31 amp draw. I have removed every single fuse I can find in the fuse box and it still reads a draw on the system. I'm stumped. Is there another circuit that could be causing this that isn't routed through the fuse box? I've gone over the ignition system pretty well, so I'm not sure it is that.

 

[Big Dave]

Horn, head lights, brake lights, interior lights. To name just a few.

Big Dave

 

[62 NovaWagon]

Courtesy lights= Glove box, ash tray, console??, couple months ago I fought that drain for three days on my truck, I found it because I went out to get something out of it after dark and as a I came up to it I saw light, looked through the window and the glove box was lit up, turned out the door wasn't fully closed, duhhh...

 

[Philip]

Have you disconnected the alternator? Oil residue and dirt on the starter post where the battery cable connects can cause a drain.

 

[Claugemire]

Thanks for the info guys! I'll do some searching including the glovebox. I will also disconnect the alternator and see what happens. I'll post what the problem was once I track it down.