Ryan Menzies

I don't know the draw of an electric clock off hand. A digital clock will draw so little the light will be off. I doubt the older clocks would draw enough to illuminate the test light. Street Rat seems to have something really pulling down the battery in a short time.

jim in oregon

yes..when I worked on my parasitic drain and found fixed it..I cut a short piece of dowell rod and gently wedged it to depress the driver's side door open button so the interior light went off..and the electric clock will draw a tiny amount of current with everything OFF but that'll NEVER draw down a battery..Jim

USAFVeteran

Yep, at least in a year or so it won't.......

Les

You've gotten some good advice for troubleshooting- I really like the simplicity of Ryan Menzies's method.

If you still can't pinpoint it or fix it, this may help. My avatar car and my'69 Vette will both kill a battery if left sitting for a few weeks without being run, even with fresh batteries. After battling this over time I finally did something that remedied the problem. Hit the link below for info on the battery disconnect switch that I got for both of them. Last night, after sitting for about 4 months, I turned the **** on the Z28 and it lit right off. About a week ago I did the same thing with the '69 after it sat 2+ months. It also makes them a little harder to steal if you have to leave them parked somewhere.

https://www.amazon.com/Post-Battery-...urn+off+switch

Street Rat

The DVM has been on the battery for 24 hrs. Checking for a voltage drain on the battery but came up empty. It was 13v when I first connected the meter. 24 hrs later it is reading 12.8v. That doesn't seem like much of a drop to me.

So I go to start it after sitting for 24hrs and it started right up. The DVM read 14.5v after the car started.

Next to do some of everybody's suggestions. I'm pulling fuses as a final test. I usually pull the seat so I can get to the darn fuse box.

suprspooky

I have a Batt. disconnect as well, the P/O installed it for a nagging parasitic drain in my 68 vert, it turned out the wiper override switch had been in the wrong position and was causing the drain (I read about the switch in the Owners Manual), I posted this in case you weren't aware, I think the 69 has the same circuit.

USAFVeteran

While any kind of battery disconnect will make it so it's not draining the battery, it's a band aid on a shark bite. Find the root cause, and fix it. This comes from working on military aircraft for a year or 2. Find it, fix it, fly it.

Ryan Menzies

Street Rat,
Hold on to pulling fuses just yet. You need to confirm a drain using the test light method we described.
What you're actually looking for is current draw. Current is essentially AMPS. The DVM reading that you are using is in VOLTS. It's great to tell you battery voltage but you want to see what amperage draw you are having. You had mentioned that you might be a little weak in the electrical department so using the simple test light trick is a simple and effective way.
Using a DVM is perfect but you'll have to have it swapped over to amps, run it in series and possibly the use of an amp clamp. Not needed for what we are doing on this car IMO.
Simple test light is going to be fine.
As mentioned above from a few folks, shut the doors, make sure the headlight switch and everything else is off.....let's see what we have found out then !

Street Rat

Oh no I wasn't going to pull fuses just yet.
Thanks for the advice. Going to hook up test light now. Will report back.

Street Rat

I hooked the test light in series with the neg battery post / cable. Immediately my aftermarket alarm started going off at half volume. The test light was lit after closing doors and courtesy lights out. The alarm would not silence so I had to discontinue this test.

Ryan Menzies

Not a bad place to start actually SR. Disconnect the power source for that alarm and see what you have then on the test light.

USAFVeteran

Disconnect the fuse for the alarm, and try again

USAFVeteran

I need to read a little farther when reading this forum sometimes.....

DUB

I read this entire thread.

I am NOT wanting to ruffle anybodies feathers....but. I am going to give my real world experiences.

Knowing that when you had the car sit for 24 hours....and it started up. In my opinion...you do not have a significant drain.

BUT...I will say that using a test light is quite useless in determining of you have a drain. The reason I 'say' this is because it is true. YES...it will let you know you have a current draw...but it will not tell you how many amps are being drawn. And I know this is the C3 section...but if you try this 'test light' method on a 1984-1989 Corvette.....you will be chasing your tail for days on end. Because the test light shines like crazy due to the 'built in' power drain. Ask me how I know this.

SO..having the correct tool that lets you actually see the amp draw is the only way to go. But do as you wish.

Keep in mind that even IF the interior lights go out...does not mean the interior timer controller has stopped drawing current. I have seen these module go bad and can eat up a battery quickly...which is why if the car lasted 24 hours..I doubt you have a drain.

Knowing that this is an 1981 Corvette...if the car had a factory alarm system..I doubt the alarm system would draw current if it was activated due to the same horns are used for the alarm system as when you hit your horn button . So if your horn button blows your horn and it makes noise...then it is not the facotry alarm system On earlier C3's...the alarm system can be set and going off and the alarm horn is drawing power but not making noise due to it being bad. I have seen this also.

A vanity mirror light being on can eat up a battery also.

But to your main problem.....and it appeared that it happened when you drove it and then stopped. It seems like your alternator/starter are good and you have already checked the common areas previously mentioned.

But here is one that can bite you.

At the rear of your passenger valve cover...by the fire wall is the wiring harness that GM installed that goes to the starter. There is a wiring harness connector that comes off the main engine harness...one half should be a clear white color and the other half is black., They hold about 6 wires. WELL...this is a major flaw from GM and this connection can go bad. Sometimes this connection gets so dirty that it heats up due to an increase in resistance and can actually melt the connectors. Just like the blower motor relay for your fan blower...which I have seen countless ones melted there. So....Check this connection out.

I often times repair this by taking this poorly thought out junction out of the equation. Earlier Corvettes did not have this junction...but from 1978 to 1982 they did.

This junction connector can be getting hot enough and expanding/failing to not make good contact and even though ALL of your other electrical stuff works...when you go and try to start the engine.( which commands the most amps of all ) the connection fails.

DUB

Street Rat

Great stuff as always DUB.
My dvm has milliamperes on it. Is that what I need to accurately detect a draw? Or is there a special tool that I need?

USAFVeteran

Dub, I wouldn't argue with that logic, you're right. But at this point, I think he may want to at least try to narrow it down to a circuit or circuits to work on. And, while it won't tell you the amp draw, it will show a draw. I've done it a few times on the 47 miles of wiring on a motorhome. Then I'll break out the tools to tell the amp draw.


We have different ways to get to grandmas house, but we all wind up there, eating pie and ice cream!!

Les

Thanks, it can't hurt to check but there's always been something else going on with mine. After I bought it long ago I noticed the back up lights didn't work, saw that there was no fuse in place for them, and put a new fuse where it belonged. It blew immediately and it wasn't pretty. I quickly removed it and never tried another one. I've never found any visible problems with the wiring but, since back up lights aren't important to me, I never spent the time or money to run it down. Everything else works except the clock, and electrical is the only system on a car that I haven't DIYed except for distributors, coils, and basic stuff. Troubleshooting- not a strength of mine at all.
Absolutely true, although it may not be as severe as a shark bite. . It sounds like he's about as well versed on electrical matters as I am, which is not very well. My suggestion was not a solution to the problem and was only offered as an option if he couldn't fix it himself.

USAFVeteran

Les, I didn't say that to be offensive towards you at all. I apologize if I came off that way. Cheers

Ryan Menzies

DUB,

I hear you but let's not put the cart before the race. The reason why we are using a test light is because is pre-anything that got too crazy in the electrical world that will take further investigation AND SR is weak on electrical. We need this simple and easy as a basic test to confirm a drain or not - or we end up talking amp draw vs. battery storage/amps per hour etc and then having to get into the DVOM.
Just simple stuff for now.

Cheers.

Les

Thanks, but I never took it that way at all. You spoke the truth and did so with the intent to be helpful. There was nothing offensive in it. By the way, sincere thanks for your service.