1972 battery drain

[abriddell]

Hello everybody,

About 2 weeks ago the the battery in my 72 eldo started draining down to zero overnight after a drive.  I leave it on a 2 amp charger now, but I need to try to find the source of the drain.

Does anybody have any suggestions for where to start?  I've done quite a bit of electrical work in my house, but not much in a car.

Thanks,
Andrew

[Scot Minesinger]

It I a good idea to have a battery disconnect on the negative terminal so that you can service the car conveniently (replace starter and etc.) and in this case as you uncover the problem, you can avoid drain while car is off.

Do have an amp probe, if not you should get a good one, plus of course a multi meter.

With car off, go to use box.  You can start with the easy stuff, remove power cigarette lighter fuse and let car sit and see if battery drain stops.  If not go to next fuse.  Alternatively if you can get the probe around a wire, testing first by say getting the probe around power window motor wire then raise an lower window to make sure your amp probe provides a readable DC volt reading.  If a good reading I visible, then with car off check every wire leaving fuse box and see which one is drawing power.   

Once you know which circuit is drawing power on the fuse box, you then need to chase it down, by actually finding the short in the wiring.  It is cigarette, power window or power lock, likely source is compromised rubber conduit/grommet at door jam/door.  Check fire wall wire penetrations to make sure all grommets are functional and no compromised wires.

It takes some time to find it, but when you do it is rewarding. 

["Cadillac Kid" Greg Surfas 15364]

Andrew,
Just out of curiosity, how old is the battery?  If it is over a couple of years and has sat in a depleated stage of charge it may be time.  Three of the most likely drains are;1. Brake lights do not go off, 2. The trunk light switch is bad, causing the light to stay on, and 3.a bad alternator.
Greg Surfas

[Jeff Rosansky CLC #28373]

If you don't have the meters, just do it the poor man's way.  Disconnect the negative cable and then just touch it to the terminal.  You will probably get a spark.  If so, then that is a drain.  Then do as Scot says, pull some fuses and see where it stops.  That will help you ID the circuit that is bad and then you can go from there.  Of course be ventilated.  If the battery is dying and giving off gasses, you don't want sparks there.
Jeff

[abriddell]

Thanks - I have some good homework!

The battery is about a 9 months old, AGM type and literally drained down over night after no issues whatsoever previously.

There is no trunk light bulb installed, but I wonder if the electronic closing latch might be an issue?

I replaced the alternator, starter, ignition coil, ignition module, and primer coil in 2013, so those are fairly new as well.  When the battery is fully charged the car fires right up. 

Thanks for the step-by-step instructions.  I should at least be able to figure out which circuit is causing the problem.

Andrew

[Scot Minesinger]

Don't forget the clock draws a current even with ignition off, o don't count that against the battery drain.  Usually you can go several months before clock will drain battery.

[Jon S]

If the battery has removeable cell caps, the first thing I would do is bring the electrolyte up to the split ring with distilled water, charge it with your trickle charger, then test the specific gravity with a hygrometer.  Disconnect the negative terminal as suggested above and then re-test the disconnected battery's specific gravity 24 - 48 hours later.  If it dropped, then you have a defective battery.

Did this "dead battery" situation happen quickly?  Did you make any changes to the car - new accessories, adjustments, etc.?  Need a little more information.

[TJ Hopland]

If you don't have an 'amp probe' or a meter with that function you can wire a light bulb inline with the battery for this test.   Something like a tail light will work for a smaller draw.    You can even 'remote wire' it.   Last time I did it I used jumper cables to get it where I could see it while I was at the fuse box.   Just disconnect say the neg wire from the battery.   Connect say the black wire from the jumper cable to the neg battery terminal then connect the red wire of the cable to the cars neg battery cable.   You then connect your light between the red and black at the other end.    If the bulb lights there is a draw.  The brighter the light the bigger the draw.  IF you overload it the bulb turn into a fuse and burns out.  IF you are expecting a big load use a big lamp like a head lamp.   Since you will be working with the door(s) open remember to first remove the fuse for the interior lights or jam something in the door so you don't have the interior lights throwing off your test.   If its a coupe remember the seat release is electric too.

I have not seen trunk releases have a constant draw.    If they get stuck on the trunk usually won't stay latched and the coil burns out fairly quickly. 

Do your horns work?  I have had more than one Cadillac where where something went wrong in the steering wheel that at one time must have stuck the horns on so someone had cut the wires under the hood.   Problem was that the relay was still engaged.   In the summer it was not usually a problem but in the cold it was enough to kill it overnight.

You said AGM battery?   Like a Optima?  Those can be pretty funky when they do get drained.  They can be very hard on chargers and or alternators and take way longer than a normal battery to get fully charged again.   Left the lights on in my truck last week and I thought I had got it fully charged but went to start up later that day and it barely started.   Next day it still would not start.   Figured the battery was maybe finally done.   Yesterday did like Optima recommends, hooked a fully charged battery up to it and a charger.   All looked well when I left it last night.   Will find out later today if its 'fixed'.     

[abriddell]

Hi TJ,

The AGM is like an Optima battery - except I bought it at Farm and Fleet.  It looks like the same battery that's sold with a Sears Diehard label too. 

I've had to recharge it twice and it reached full charge overnight both times. 

Clock doesn't move at all - but it's right twice a day.

No new modifications to the car.  There is an aftermarket intermittent wiper control that doesn't seem to be working. 

I tried Jeff's spark test but didn't find anything.  I'll try again with the jumper test.  If I don't find current coming off the battery with the car off and key out of the ignition, then can I assume it's the battery itself?

One thing that's a little weird is that the buzzer keeps sounding for a second after I pull the key out.  It usually goes off by itself but sometimes I need to tap on the ignition switch to kill it. 

Andrew

[TJ Hopland]

For the light bulb test I described above you don't need something as heavy as jumper cables it just works out that most people have a set and they have the clamps already on them to make it easy to connect under the hood.     Its a good idea to work with the NEG (or grounded side if its a POS ground system) because if you accidentally bump something to the body all that will happen is you are making the 'normal' connection.   IF you were working with the non grounded side and you bump into the body you will have some sparks. 

[abriddell]

I disconnected the NEG battery terminal, and then used my multitester to test for continuity by using the probes to jump the POS battery terminal to the NEG battery cable, which was disconnected.   

The first test was with all of the fuses in place, and then I removed one at a time for the rest of the tests. 

Do these results mean anything to you guys?
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[TJ Hopland]

The test you describe does not really test anything useful for the issue you are having since you don't have a complete circuit.    To test for a draw you have to have a complete circuit meaning the POS and NEG have to be connected.   Some multimeters have an amp testing option.  To use it you need to plug the probes into different sockets.   You then set it to the proper setting and hook it inline / series to the system / circuit you are testing same way as I described hooking up the test light.   Trick is a typical good meter will only have a 10 amp limit / range.  They usually also have a milliamp range.  10 amps is pretty easy to get on a car, it does not take many lights to get that load so you have to be careful or you can damage your meter.   You also have to remember when you are done taking that reading to plug the probes back into their regular holes or you will get a big bang next time you try to read voltage on something.     There are also meters that have and inductive pickup that you just clamp around the cable you want to test.  These used to be very expensive but were easier to use.  Prices have come down a lot but they still are somewhat expensive especially if you want one that is somewhat accurate.

Here is an example of a typical digital multimeter.  I'm not recommending this model or vendor, just using it as an example.  If you go to a manufacturer of quality measuring instruments like Fluke there are just too many models and options to use for a quick example.

http://www.harborfreight.com/ac-dc-digital-multimeter-37772.html

Its got an amp checking option where like I described you have to re plug the probes to a different jack and then actually hook the meter in line.

Here is an example of an inductive one.  Again same disclaimer as above. 

http://www.harborfreight.com/digital-clamp-on-multimeter-95652.html

You just 'clamp' the probe end around the cable you want to check.   Note that this particular model does not read DC amps, only AC so it would not do you any good on a car.   Models that read DC have always been more expensive.   I have both a genuine Amprobe one and an FW Bell that I have had for many years.   Both were $100's 30+ years ago when I got them.

[abriddell]

I was afraid of that.  I'll try again and see what I can find...

The tester I have is a Sperry DSA 400 and it does have a clamp like the second example.

Andrew

[R Schroeder]

If your not getting any spark off the battery cable as you touch it to the battery, I would say you have a bad battery, if it dies over night. My battery will power a clock all winter long.
Roy

[abriddell]

There is a very little spark coming on the NEG terminal when I touch the cable to it.  Couldn't see it before. 

So, the battery is probably in decent shape and there is a drain somewhere in the system. 

["Cadillac Kid" Greg Surfas 15364]

Andrew,
Did the car ever NOt drain the battery overnight? If so, what has been done to it prior to that symptom starting?
Greg Surfas

[abriddell]

It used to happen a lot but I haven't had problem since I installed this AGM battery and let it sit on a trickle charger if I don't drive it for more than 24 hours. 

It's like the battery just crashed all of a sudden.  I took it out completely today and charged it on my workbench. 

[35-709]

I have had a clock drain the battery overnight, the points stuck together and would not release.  Things apparently got quite warm as the clock face/clear plastic cover had a dark cloudiness to it the next day.

[cadillacmike68]

It used to happen a lot but I haven't had problem since I installed this AGM battery and let it sit on a trickle charger if I don't drive it for more than 24 hours. 

It's like the battery just crashed all of a sudden.  I took it out completely today and charged it on my workbench.

OK. wait a minute here.

You have been keeping it on a trickle charger for quite a while now?  And in the past few days the battery has drained even with that charger, or did you take it off the trickle charger a few days ago and that's when it drained??

This is looking like a battery problem, but if it is not the problem is most likely in the horn circuit - they can go bad in the wheel switches or at the relay. Or it is probably a body circuit (all the interior lights, lighters, etc.) problem. Door jamb switches are part of the body circuit, and they can go bad too.

I would have the battery checked out first. Do you have one you can swap in?

[Jeff Rosansky CLC #28373]

I would suggest you charge the battery as normal and then let it sit a day or so unhooked.  If the car starts, it is the car.  If the car doesn't then it is the battery. 
I am not a battery guy but the AGM batteries have a reputation of being tricky once they have drained fully. 
Jeff