IBEAM700

Hello All

I’m a C4 owner, but im working on a friends 1972 Convertible, and im having some electrical issues. First iv got a battery drain problem. The ammeter reads 2.61 milliamps with everything turned off, and 3.01 milliamps with the car running, so as you can see this Vette is pulling almost as many amps off as it is running, which in turn drains the battery in short order.

Work performed so far: With the ammeter hooked up I pulled all the fuses, still drawing 2.61ma, pulled the cables of the alternator, still drawing 2.61ma, pulled the battery cable off the starter, still pulling 2.61ma. I’m at a loss here.
I’m in desperate need of an electrical diagram for this car; can anyone email me one, or direct me to a webpage that might help?

Thanx :chevy

mrvette

Ibeam, I have a diagram, and it's for MY '72 convertible...not that mine is stock by any stretch...you need take the terminals off the horn relay on the dirvers' fender liner...one at a time, and measure just what and where is drawing current....ther is a red wire running through a fusible link (thin wire acting as fuse) from the battery post + at the starter...so you need disconnect everything and measure to locate that main power wire, and then make sure somehow you are NOT drawing any current from the battery with it and everything else loose in the air....then connect the main power wire through an ampmeter to ONE of the other terminals at a time....

somehow I"m betting it's an alternator related thing.....
OH, you may need to cut the tape and retape as necessary...messy I know, but maybe to prove the point....

GENE

IBEAM700

Hi Gene

I don’t have the 72 Vette with me at the moment, but im going to pick it up tomorrow and bring it home so I can better diagnose it.

Do you now if the positive batty cable branches off anywhere under the car before it gets to the battery? Because I was under the impression the main positive battery cable runs from the battery to the starter, and then from the starter feeds the rest of the car.
Thus when I remove the main positive cable from the starter the rest of the car is not hot.

Brian

mrvette

Brian, you are totally correct, BUT that applies to stock system wiring....IF someone did something differant for say stereo hookups or whatever they thought of...all bets are off.....

certainly there is NO point in doing much differant from the stock wiring with the main power feeds, but well.......let's put it this way, I"m an old phart TV shop manager, and as such have seen so much terror you just can't imagine....

GENE :D :D :D :nono: :nono:

IBEAM700

Gene

I know what you mean about “butchering” of the wiring. I’m kinda lucky that know one messed with this electrical system to much. I have ran across a few jury-rigged items, but considering the age of the car the electrical system is in pretty good shape.

Let me run this by ya, just to make sure my multimeter was working correctly I ran out to the C4 vette, and my S10 pickup, and both of those vehicle are pulling 2.7 to 2.8 milliamps. Now im totally confused because I thought these systems were supposed to pull less than an amp when turned off.
All im doing is touching my multimeter leads to the battery positive and negative terminals.
This IS the correct method right?

Brian

greg454

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and both of those vehicle are pulling 2.7 to 2.8 milliamps. Now im totally confused because I thought these systems were supposed to pull less than an amp when turned off.
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2.7 milliamps is way less than an amp. there are 1000 milliamps in 1 amp. 2.7 to 2.8 milliamps is just fine, thats probably what is keeping your radio presets and clock correct.



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All im doing is touching my multimeter leads to the battery positive and negative terminals.
This IS the correct method right?
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If you hooked up your ampmeter directly to your battery + and - terminals
then you have blown the fuse in your meter! A ampmeter needs to be placed in series with a load such as a light bulb or a motor that would place some resistance in the circuit, a ampmeter by itself would be a short circuit. The only meter you can put directly on your battery is a volt meter. The correct way to see current drain is to remove only the ground lead from the battery and then hook your positive test lead to the battery negative post, then hook your negative test lead to ground. your meter needs to be set to amps and the test leads plugged into the correct spots on your meter to read amps.

hope this helps
Greg :cool:


[Modified by greg454, 3:57 PM 8/15/2003]

IBEAM700

Hi Greg

Thanx for the reply. I guess I was reading 2.7 as 2700 milliamps. Even when I place my multimeter on the Amps setting it still reads 2.7

I must have an idiot proof multimeter because it’s still working after the battery +/- terminal encounter. :lol:
I did run the multimeter in series with the negative batter cable and the negative battery terminal, and the reading was 2.1
I do not doubt you, because three properly working vehicles here at the house have proved me wrong.
All three read between 2.7 and 2.8 milliamps

IBEAM700

Update: Well im not sure what I did, but the electrical system seems to be ok as of now.
I just cleaned the battery terminals, and checked the connections at the horn relay per mrvette. All seemed ok, but I sprayed some WD40 on em anyway just to drive out any moisture, and break up the loose rust.
I’m still monitoring it, but everything is working correctly.
When the engine is running the voltage at the battery is just over 14 volts. When the engine is off the voltage at the battery drops to 13 volts, and falls to 12.87 when let sit overnight. Ill keep ya updated.