I have a dead short somewhere on my "92. After a week or so of sitting the battery goes dead. I noticed while disconnecting the battery ground cable the left hand headlight motor clunks.
The manual raising/lowering **** moves about one degree. The motor raises and lowers the headlight fine. The right side doesn't clunk. I'm guessing this is the cause of the battery drain, but at a loss as to why it does this.
Any ideas? TIA
Dave

 

Disconnect both sides of your head light motors and see if reconnecting the battery still causes the drain. If the drain still exists you will need to start removing fuses to identify/isolate the cause and go from there. If the head lights are the casue you may have to consider a motor swap/rebuild. The motors are finicky at best and there is no telling what happened to the internals after all these years.

First thing you have to do is to isolate the circuit that has the drain.

 

Bill:
Did that with the meter on. No change. Drawing 1.76ma. Not 0.176. Big draw. So I did the fuse thing and even the relays in the fuse box. No change.
Disconnected every electrical connector and relay under the hood I could find. One at a time of course. Also, disconnected all the hot wires on the common stud behind the battery. Wiggled and jiggled wires. No change.
Out of ideas. Your thoughts? Anybody?
Thanks Bill.
Dave.

 

Disconnect the alternator. See if you get a change....

 

Dave, we have a major problem with terminology, and correct terminology is important for an understanding!

With a "dead short", you'll have major sparks when you connect the battery, and the battery might even explode. That would be caused if you connecting the + terminal of the battery and the - terminal together! Your "week or so" causing a dead battery does not qualify as a "dead short".

Your measurement of 1.76mA tells me you aren't making your measurement correctly. If that were true, your battery would be good for many months! Can you see why I'm confused? The normal residual current draw should be between 10 mA (0.010 A) and 50 mA (0.050 A).

Questions:
1. Is your DVM auto ranging, or do you need to turn the selector **** for different maximum current measurements? How would you rate your electrical skills?
2. As you should be aware, your Corvette has several accessories that go thru an initial electrical shut down delay after you close up the car. This causes an initial higher current drain, before going to a low current drain after a few minutes. We usually call this "going to sleep".
3. Here's the correct procedure:
4. Hood up (for access to battery).
5. Disconnect (or remove) hood lights.
6. All accessories and lights off.
7. Doors closed.
8. Disconnect battery (either post).
9. Install a jumper wire between the battery post and the battery cable. You'll notice that the interior lights come on. Wait for about 30 seconds AFTER the lights go off.
10. Connect your DVM (set up to measure Amps) between that battery post and the cable (polarity doesn't matter). The reading should be ZERO.
11. Remove the jumper wire, WITHOUT DISCONNECTING THE DVM!
12. Your DVM will show the accurate residual current drain. Ignore the + or - of the indicated current drain.
13. Please give us your number.

 

HRR:

My electrical knowledge is somewhat lacking. I'm an ME not an EE. I slept thru most of the electrical courses in college. Except for Ohms Law I don't remember much, didn't interest me then. Does now.
I should have said I have a parasitic draw.
What I'm working with is a Klein MM400, and an El Cheapo from HF. Getting way different readings. On the Klein I get 1.76ma. The HF 0.01ma?
Yes. I read the instructions and to the best of my knowledge there're hooked up right. Weird thing is; If I reverse the leads on the Klein (red on the battery cable and black on the battery post) the reading changes to 2.5ma. Not suppose to matter, but it does. I think I'm missing something. HF unit doesn't matter.
I'm missing something setting up the Klein.
The instructions say:
For mA DC currents <400ma Insert the RED test lead into the V/ohm jack and BLACK to common. Rotate the selector dial to ma DC setting. I get 1.76ma
The other option:
For DC currents >400ma and less than <10A. Insert the RED lead into the 10A jack, and BLACK to common. Rotate the selector dial to 10A DC. I get 0.000A.
So I used the instructions for ma DC currents. I'm I wrong?
Yes, every thing is timed out. Battery has been hooked up to the meter(s) for days.
With meter(s) on I disconnected every electrical connection and relay under the hood. Disconnected the alternator and even the starter and solenoid. No change.
Did the one fuse at a time thing along with the circuit breakers in the fuse panel, Nada.
I started this quest because every time I disconnect/reconnect the negative battery cable, the left hand headlight motor makes a clunking sound. So naturally I thought that's the problem. But with the meter on and the connector disconnected, there is no change.
So by applying the parable on the blind hog and the acorn, I'm not having much luck.

Thanks for your help Roy.

 

It sounds like you have a blown fuse inside your Klein DVM, probably the same story on the HF meter. Some HF meters wont even measure anything below 100 mA (0.1 A).. If you didn't use my "jumper first, then wait" technique, you'll blow that fuse.

 

Meters seems ok. Not familiar with "jumper first, then wait' instruction.

 

How did you determine "meters okay"?

Please review post #5, steps 8 & up.

 

When you say all the fuses are removed, does that include the aux fuse panel above the passengers feet? The ones that you have to drop the hush panel for?. The hood light fuse by the left front corner light? Point being, the fuse block on the right end of the dash is not all of the fuses.

 

Was not aware of the other fuse panel. Headlights are both disconnected as the hood has been up for about a week.

Thanks Brian.

 

Understand. Didn't use the jumper as the battery has been disconnected for about a week. I will do that though.
Actually brand new meters. The Klein I bought to measure DC Amps as my old one didn't have that feature. Just DC Volts, Ohms with a AC Amp clamp.
The HF one has been sitting around for about a year still in the bubble pack. Was a freebie with some purchase. They lit up and measured voltage but not Onms.
But, to be on the safe side I ordered new fuses. After thinking about it I checked the fuses for continuity with my old amp clamp meter. All seem to be toast.
Good catch on the fuses. Don't think I did anything to make them blow. Just the standard amp draw thing. Maybe I turned on the meters and then connected the leads?
Would that do it?

Thanks Roy, appreciate your help and patience.
Dave.

 

You MUST use the jumper.

That's got nothing to do with the issue.

Please see post #7.

 

Roy:
Ahhhhhhh...I think it finally sunk in. Without the jumper the meter takes the initial surge. Was going by a few youtube videos I watched. They didn't use a jumper. Then I found one with a yellow C4. And then my light went on. As you may have surmised, my light is not very bright to start with. When my new fuses come in I'll go at this again. I'll let you know.
Thanks again for being a great special-ed teacher.

Dave.

 

HRR knows his stuff! You're in good hands with this thread.

 

HRR:

2.5ma. Understand less than 5ma is normal.

Dave