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Battery Voltage


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Hi all,

 

I just purchased a new to me 1964 Buick Riviera. Full disclosure, it is my first classic car - so I am excited to learn and enjoy the hobby. First order of business - I am trying to figure out why the battery seems to be drained. Battery is 6 months old with receipts. I read a few forums regarding battery drainage and did a few tests on my end and here is what I have found.

 

Car will crank but not run - Multimeter showing: 11.4V

Battery trickle charger on - Multimeter showing: 12.51V by AM (about 8 hours of charge)

Car turns on - Multimeter showing: 14ishV

Drove it 10-15 min @ 20mph (car still needs to be registered and insured) then parked - Multimeter showing: 13.7V

Car is turned off in garage - Multimeter showing: 12.6V

 

Wondering if anyone can lead me in the right direction or if this is normal.

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5 minutes ago, 1964Rivi said:

Car turns on - Multimeter showing: 14ishV

Drove it 10-15 min @ 20mph (car still needs to be registered and insured) then parked - Multimeter showing: 13.7V

Car is turned off in garage - Multimeter showing: 12.6V

Those readings indicate that the standing battery voltage and alternator/charging voltage are OK, so the battery is being charged when the engine is running.  If the battery goes dead after sitting in the car for awhile, that suggests there is something in the car that is on and drawing current when the ignition is off.  You can verify this by disconnecting the negative battery cable and connecting your meter (set up to read Amps using the highest scale) in series between the negative terminal and the battery's negative post.  Ideally the current should read "0" amps.  Aside from an occasional blip to self-wind the clock, I can't think of anything aside from a late model radio that may draw any current with ignition off.

 

If current reading is not zero, check that glovebox and trunk lights are off (remove the bulbs).  If that checks out, start removing fuses one at a time until you find the circuit that is drawing current.  That should at least narrow the search.

 

Oh, also check that there isn't a wayward penny or dime in the cigarette lighter socket.  People would throw loose change in the front ash tray and sometimes one of the coins would find their way into the lighter socket.

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EmTee,

 

Thanks for the quick response. I will do try all of those later today and report back. The original sonomatic radio is in the car, so I will make sure that is not on in any capacity.

 

 

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Posted (edited)

Following on from EmTee,--if its still not 0 reading after doing all that, go under your dash and

remove each fuse one at a time check with your meter across, , or better a cheap small wire test light across

each fuse, if you get  a dim light or meter shows  power at that particular fuse,---thats the item that is causing the drain.

 

Edited by Wayne R (see edit history)
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24 minutes ago, 1964Rivi said:

EmTee,

 

Thanks for the quick response. I will do try all of those later today and report back. The original sonomatic radio is in the car, so I will make sure that is not on in any capacity.

 

 

 There are two sides to the fuse box, the IGN side and the BAT side.  
 

The IGN fuses are only hot when the ignition is on ( key in on or run position.)

The BAT fuses are connected to the battery, hot all the time.  
Your radio fuse should be on the IGN side. It should play only when the ignition is on.  

 

Most of the guys on this forum have found that possessing a Chassis Service Manual is the best tool in their shop. Second would be a Body Manual.  You can find quality reprints or CDs on eBay.  Well worth the investment.

 

Good luck. No one likes chasing electrical,gremlins.

 

Ed

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2 hours ago, EmTee said:

Those readings indicate that the standing battery voltage and alternator/charging voltage are OK, so the battery is being charged when the engine is running.  If the battery goes dead after sitting in the car for awhile, that suggests there is something in the car that is on and drawing current when the ignition is off.  You can verify this by disconnecting the negative battery cable and connecting your meter (set up to read Amps using the highest scale) in series between the negative terminal and the battery's negative post.  Ideally the current should read "0" amps.  Aside from an occasional blip to self-wind the clock, I can't think of anything aside from a late model radio that may draw any current with ignition off.

 

If current reading is not zero, check that glovebox and trunk lights are off (remove the bulbs).  If that checks out, start removing fuses one at a time until you find the circuit that is drawing current.  That should at least narrow the search.

 

Oh, also check that there isn't a wayward penny or dime in the cigarette lighter socket.  People would throw loose change in the front ash tray and sometimes one of the coins would find their way into the lighter socket.

Dead on the money advice.  Plus look at the rear trunk light as a possible source of the drain

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The reason the guys are suggesting the trunk light is because it ‘automatically’ comes on when you open the trunk by way of a mercury switch. If it has failed, the light will stay on. Just remove the bulb to check it out ( unless you want to get into the trunk, close it, and trust your wife to reopen it.)

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All advice given so far is sound advice in my opinion. I would add that if you dont have a meter to check current flow an alternative preliminary check before you start pulling fuses is to check for sparks when disconnecting battery cable with ALL SYSTEMS OFF. If you see sparks proceed to the fuse pulling step. If no sparks, no need to pull fuses because there is no load on the electrical system. You can also use this technique in conjunction with pulling fuses to find a current drain. Best done in a garage with the least amount of light you need to work.

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A test light can also be used to check for current draw if you don't have a meter.  Connect the light between the disconnected negative battery cable and the negative battery post.  The light will glow in proportion to the amount of current being drawn by the short, or accessory that is 'on'.

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On cars of that era, 99.3 percent of "draw" problems fell into two categories.

     1) Glovebox lights (including console lights, trunk lights, etc.).

     2) Borg clocks.

 

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Another place to look is the rear seat.  Has someone flipped the switch on the back of the console for that light?  Hard to see if you're not looking right at it.

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Posted (edited)
On 6/1/2024 at 6:45 AM, 1964Rivi said:

Hi all,

 

I just purchased a new to me 1964 Buick Riviera. Full disclosure, it is my first classic car - so I am excited to learn and enjoy the hobby. First order of business - I am trying to figure out why the battery seems to be drained. Battery is 6 months old with receipts. I read a few forums regarding battery drainage and did a few tests on my end and here is what I have found.

 

Car will crank but not run - Multimeter showing: 11.4V

Battery trickle charger on - Multimeter showing: 12.51V by AM (about 8 hours of charge)

Car turns on - Multimeter showing: 14ishV

Drove it 10-15 min @ 20mph (car still needs to be registered and insured) then parked - Multimeter showing: 13.7V

Car is turned off in garage - Multimeter showing: 12.6V

 

Wondering if anyone can lead me in the right direction or if this is normal.

That sounds normal, except for it being low at the beginning. Are you having trouble with the battery going dead over a couple of days or was it just low once?

 

The natural voltage of a fully charged 12V battery is 12.6 Volts. You probably won't always measure exactly that, but something close. When the engine is running you can expect more than 14 volts. I suspect it was probably about 14.2 or 14.3 Volts at room temperature back in 1964, and probably more like 14.7 at room temperature now if the regulator has ever been replaced.

 

Edited by Bloo (see edit history)
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Just updating everyone on this post:

 

After gaining the courage to take the trickle charger off and see if the battery drained, I found that it didn't. Just for sake of checking, I checked for a parasitic drain and there was no draw from the battery with the negative terminal disconnected...The battery has been sitting at 12.7V since and hanging steady. My only guess is that my amateur self turned the key all the way to the left when turning the car off, thus putting the car in ACC mode which in turn drained the battery.

 

Thanks for all the tips! I'm sure many, many more amateur posts will come from my account...

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11 hours ago, 1964Rivi said:

I checked for a parasitic drain and there was no draw from the battery with the negative terminal disconnected...

Just to be clear, you saw no draw with the ammeter connected between the negative battery post and the negative battery cable's terminal (cable disconnected from the battery) - correct?

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