Hardscrable

Bills17n72

im guessing your clock or maybe the burglar alarm,,on my 72 the clock worked ,but didnt keep the right time ,and no issues ,but all of a sudden I would have a dead battery after a few days ,pulled the fuse for the clock ,and the problem was solved

henrikse

You do have a fusible link by firewhall at wiper motor for ammeter. Mine wasn't working and this is why. You are going to have to get a meter connected in series with battery cable pos or neg and see what kind of current you are drawin? Remember with courtesy lites on you are going to draw some.current. Close the door and should be 100 milliamps for clock. If more then start removing fuses.(tape door switch closed with duct tape) and see when you lose the draw. Now you know the circuit so follow thru. You will need a wiring diagram.

DUB

I agree that 100 milliamps is fine and your battery should not go dead.

If you get like 300 milliamps you are now getting on the borderline and the battery can go dead in a short time.;..such as a month of no usage.

I have seen the light for your rear glove box fail and that can do it. due to the door is not fully compressing the switch for that light.

The only circuits you need to be worried about are those circuits that have power on them regardless if the key in the ignition is turned on or not. Assuming that no has gotten in on your wiring and did some crazy stuff.

Even though your amp gauge is not working...you can still test and see if your alternator is charging at the battery. Because the alternator does not miraculously stop working if your amp gauge fail to work.

DUB

HeadsU.P.

Keep in mind that when these cars were new they sat on the car lot for weeks at a time, maybe a month. No clock or alarm should run down a battery. However, today if something with more draw is on that same circuit as the clock, well then . . . . .
Who knows what's hooked up to circuits after 40 some yrs.

Any time the vehicle is not to be used for over two weeks, a automatic trickle charger (Deltran Battery Tender) should be employed. Only takes 30 seconds to hook one up. Adds longevity to a battery and will monitor if there is a "draw" issue if the Tenders light changes from green to red.

croaker

Hamerdown

Always a Tended used here, but here's a new one for ya;
My Tender will keep the battery at 12.82 volts when in car...green light on.
Out of car, Tender will hold batter at 13.2 volts...green light on.
Why can't Tender hold 13.2 volts in car...something drawing hard?

henrikse

Sounds about right.You are going to have some draw on a battery in car. Clock or small amount of resistance in cables . You can put an ammeter in series with one of the battery cables and see the load.

Hamerdown

Nope, door not open and no lights burning.
Yes, an aftermarket stereo, no display when key is off but does have a memory for time and station presets.
A Battery Tender brand 'tender' will hold my new battery at 13.2 volts when the battery is out of or disconnected from the car with green light on Tender.
However, with the battery connected to the car and I check voltage with a meter the Tender only holds it at 12.82 V still green light on Tender but a happy battery should be at 13.1-13.2 volts

Peterbuilt

Hi Hamerdown,
After temporally disconnecting the battery, disconnect the RED wire from the alternator and reconnect the battery and see what your tender voltage reads.
Maybe the alternator is bad.

Hamerdown

Well thanks for that suggestion, few months ago I accidentally did touch the Alt terminal with a grounded wrench...the sparks were lovely lol
But it does charge the battery when running...could it do that and still be bad?

DUB

I do not know if I am reading all of this right. BUT a battery in a car when the key is off is JUST FINE if it is at 12 volts or slightly higher.

When the engine is running that voltage will go to a higher reading and can be 13.2 or 13.4 volts DEPENDING on how low the charge is in the battery. So really low battery may show 14.4 volts when the engine is running for a while and then it will come down to about 13.2 to 13.4 volts.. SO if your alternator is charging the battery when it is running...there is nothing to worry about.

Worrying that you battery is not at 13.2 votls when it is just sitting there in the car and it not running is a waste of time in my book and has no merit that something is wrong....regardless if a battery tender is installed or not. And if your car were in my shop that is just what I would tell you UNLESS you want me to charge you a bunch of money on a repair that does not matter.

Now if you feel my professional opinion in this is all screwed up and I am wrong .Than that is your choice to do that. But I can tell you that I have dealt with enough bad charging systems and power drains that I kind of know what is going on and know where to spend my time in a repair instead of worrying about stuff the at does not matter in the long run. I have never ever had a Corvette have a battery in it that when I checked it when it was just sitting there and the engine not running be at 13.2 volts or higher.

If the battery tender is keeping the battery to 12+ volts...it is doing fine and do not worry about it. And why it is different when you have the battery out for the car and it is hooked up also makes not difference as long as it is doing what it is supposed to do when the battery is in the car and the tender is connected.

DUB

Richard454

EXACTLY-
The battery BRAND NEW fully charged will be ~12.6-12.8V (unless it's an Optima yellow top which will read just over 13)

Since you shorted the alternator- I would put a meter AT the battery and read AC voltage- yes ALTERNATING CURRENT. If you see more than .5V (POINT 5 - or ˝ a Volt) AC then your alternator is damaged.
Smoke is really hard to put back in electronics.... The DC battery in your car can handle a little AC- in fact that's part of its job other than starting your car to filter the AC voltage not filtered out by the Alternator

Richard

Hamerdown

My longtime understanding of vehicle batteries has been...'if it's above 12.50v to 12.60 to maybe 12.80 the battery is healthy. Anything under 12.40v it was starting to fail or show its age.
True, my new Vette battery on the shelf showed 12.80v sitting.
When purchasing a new battery I always take my meter and get the latest build date AND a battery that shows the highest sitting volts. In my mind a higher reading is better, let someone else buy the battery with 12.50 volts.

As to my original 12.80v comment with the Tender hooked up to an 'installed battery' vs the Tender floating it at 13.2 Volts with the battery disconnected;
this all started with the recent purchase of an AGM battery for my Harley (I always used the type that I added acid to) and coming to find the decades old type battery-tender I used on my wet cell Harley battery was not compatible with the AGM batteries to 'hook it up and forget it' (during the off season)

So, I purchased a Schamucher 'smart charger/tender' that works on all batteries except Lithium Ion.
Reading the tenders manufactures information, it clearly states; "when the battery is first connected it performs a 'test' to see if battery is good and if so will quickly charge the battery ramping it up to 14.5 + - volts and I have conformed that (real time) with my meter. Then, the new charger/tender slowly brings the battery down to and will hold it at an "optimum" voltage of 13.2 and then occasionally 'work' the battery at different voltage levels vs being at a stagnant voltage all the time. So THAT is were I'm getting my 13.2v information at for maintaining a healthy battery. In the old days I would think that was too high!
Another odd observation... with my Vette vs Harley...with both batteries in and hooked-up, and the charger/tender is applied, the Harley battery WILL ramp-up to 14.5 volts and then come down to 13.2 (where the instructions state) is optimum level for a healthy battery.
However, when the Vette battery is hooked-up to the car and lets say standing voltage is 12.60 and I apply the 'charger/tender' it will NOT charge/ramp-up to 14.5 volts...but will slowly take the battery to 12.80 and that's it.
It will ONLY ramp-up the Vette battery to 14.50 if the battery is disconnected from the car, I find that interesting!

I ALWAYS appreciate good information and the time people take to post it, at 60 years of age I am always willing and wanting to learn something new.
While I can tackle anything mechanical, when it comes to electronics and diagnosing those types of issues it's like like a foreign language to me and difficult to connect the dots...I need it to be explained to me on an elementary level and very basis step by step instructions. (thus the ECM issues in my other thread...pulling my hair out)
Thanks for the feedback fellas, I will put a meter on my battery (meter set to AC) and test to see 'if' my alternator was damaged and/or if it is drawing hard when the car is sitting.

Richard454

Reason why? When connected to the car- the charger is not only seeing the internal resistance of the battery...but the clock and/or aftermarket stereo

sambrand

also theres the possibility your battery is not in tip top shape, volts are a measure of amperage and resistance, if the battery has a weak cell it may not be storing enough amperage, only real way tot ell is have the battery tested.
amperage is the key, I wouldn't get too concerned if a voltmeter is showing odd duck measurements, volts are just a piece of the overall picture.

HeadsU.P.

We have two people with two questions because of a high jacker. Its getting confusing which answer goes to which question.

DUB

I agree.

I did what I could and I am out due to the original thread starter has not come back in and asked anything else..

DUB

Hardscrable

BlackC3vette

I hope things go well for you and I wish you the very best in your endeavors.