roosgunboss

68 Cutlass Convertible. Battery kept dying, so I took the battery in to the shop and it checked good. Put in the car and put a meter in line and it showed no parasitic current draw. Read that it could be the diode in the alternator so I replaced that. Went away for 2 weeks and the battery was completely dead (wouldn't even light the courtesy lights). I'm installing a quick disconnect tomorrow, but hate opening/closing the hood. Any suggestions on what I'm missing?

classicmuscle442

Best way to check for draw is with amp meter, either disconnect ground cable and put in line or use one that goes around cable. Digital meter will be more accurate. Does car have a newer stereo that remembers stations?

roosgunboss

Yes it has a newer "station remembering" radio. I put the meter in line as you say and it showed no current flow when the car is shut off. A radio shouldn't draw enough to kill a battery in 2 weeks?

classicmuscle442

Meter type? There has to be a draw or the radio would not remember stations.

roosgunboss

Multimeter set at 10 amps then switched to mili-amps - showed 0 current draw

Fun71

Depends upon the current drain. My Jeep battery goes dead after a couple weeks of sitting, and it has an aftermarket alarm. A while back I calculated the amount of energy drained from the battery over a 2 week period and was surprised to find it was enough to cause the battery to be depleted enough so the engine wouldn't crank.

I also had issues with the battery draining from the console light staying on, the rear view mirror map light left on, and the dash map light inadvertently turned on when I ran the duster across the dash. Couldn't see that the lights were on in daylight, but it was obvious when taking a look at the car in a dark garage.

Fun71

Did you verify the meter read correctly using something like a AAA battery? I ask because I have seen a lot of blown fuses on ammeters over the years.

roosgunboss

No I didn't check with a AAA battery. It's a new multimeter and it read correct voltage on the battery.

oldcutlass

What is your battery voltage with the car off? A bad cell can load a battery internally, sometimes it will even accept a charge, but quickly discharge it self.

Fun71

The voltage meter does not have a fuse, but the current meter does. It should have two fuses, one for the Amp range and one for the miliAmp range.

classicmuscle442

Don't leave the battery connected in my old cars, use the battery disconnect on negative battery terminal. This type of battery drain is hard to pin down. Do you have light package with under hood/trunk lights?

Vintage Chief

Whose shop? I'm still suspecting the battery.

How old is the battery? What is the date stamp on the battery?
I do this the old fashioned way.
Do you have a battery acid gauge bulb tester? You can charge a battery to capacity and test a battery fully charged, but if the electrolyte isn't of sufficient ions, or your plates are falling apart, the battery is toast and will slowly lose it's ability to maintain the charge.
You can take a battery to some shops and they'll test the battery (if the person running the test knows how to run the test under load) and they'll say the battery is holding a load. Again, I've had automotive parts store employees not know how to test a battery under load because they simply didn't know how to set the tester up.
I test the battery at full charge. Charge the battery to maximum capacity. Check the battery at full charge - it should read ~13.6V.
Take the car on several rides. Test the battery again. If the alt is working correctly, you should still be ~13.6V. Obviously, if you're far below this in the 11.9 - 12.1 range, the alternator isn't recharging the battery.
Then, test the battery while the engine is running. The alternator should be supplying well above 13.6V to the battery (closer to 14V - 20V).
Then, remove both the + & - battery terminal wires & test the battery daily as it just sits there. Is it holding a full charge over an extended say 48 hour period? If not, the battery is toast.

Vintage Chief

I just read (above^^) what the -other Eric said. I think that's the issue, IMO.

RetroRanger

a while back i was diagnosing a batt going bad and couldnt get a reading on my meter after much futzing about i found the 2 aforementioned fuses, replaced them and found my current draw....

matt69olds

If the car really has no parasitic draw (which I doubt, the radio memory will pull a few milliamperes, and that would show up on the meter) then unhook the battery. See if the battery goes dead after a week or 2. If it dies with nothing connected, you know the trouble is with the battery.

Koda

A running mechanical clock will kill a battery on a sitting car in a week or so.

roosgunboss

Thanks all for the inputs.I checked it with a hand held tester that said it was good and then took to PEP Boys to put it on their test machine and the readout said good. Battery is disconnected and showing 12.91v. Will check daily.