Traud

New to the 911. Recently purchased an '82 Coupe. Seem to have a small electrical drain. Over a period of 7 - 10 days, the battery looses it's punch to start the car. The battery is one year old, Optima dry cell, which I have determined not to be the problem. Any ideas as to how to sort this out?

Mike Traud

theiceman

i am not sure that it is that unusual to drain in that amount of time without ever starting it . But never the less.

Do you have a factory or other type of alarm ? that would be a good place to start.

other than that after everything is off monitor the batery drain.

hook up a multi meter in series in between the battery and your disconnected main lead and see what the current draw is. Then post what that is.

I am not sure what kind of life to expect from an optima before being discharged

TroyN

Right, assuming it's not clearly some aftermarket addition like alarm, RADAR detector, stereo, then you can try to narrow down where the current draw is coming from by checking current draw at each fuse location. With the ignition off there shouldn't be any draw so if you find any you have an idea of what it is that's doing it (hopefully).

As said above though, I've seen a lot of threads on Optimas and it seems they don't hold a charge as long as a conventional battery.

JBrown

I have had optimas in all my cars including my 83sc. I let that car sit about a month at a time in the winter and it fires up like a charm every time. Unless you have a bad battery, which i have seen alot. That is not your problem. I would make sure my alternator is charging correctly first. It is a very easy test. Put you multi meter on the battery, while the car is running. You should be at least at 13.2 volts. Very good would be closer to 13.9 volts. These numbers are at idle. If that is fine then do a draw test. I dont know what the factory maximun draw when off is for these cars. You can usually find out from the dealer. Put your multi meter on amps. Take off the neg battery terminal and put the multi meter in series between the battery neg terminal and the line you disconneted. That will tell you the draw. If it is within specs, you have a problem with your battery. If it is drawing to much. Then you have to start pulling fuses and see which one drops down the draw and see what components are conectted to that fuse. First place to look is at aftermarket equipment but that is not definetly your problem, so don't start ripping anything out untill you find the problem. Sorry so long. I hope that helps.

Traud

Thanks for the advice and where to start on troubled shooting. I will check the Optima battery. Forgot to mention that the previous owner installed a stereo with a CD changer. When I first looked into this, I discovered the changer made "noises" when the ingition was off. I removed the changer and went a few weeks - the problem returned. Wondering if the stereo "head" in the dash could be causal to a drain.... I'll get out the volt/ohm meter and initiate a few tests.

Mike Traud
'82 911SC

Edgy01

As you're discovering, most of the voltage leaks come from secondary market alarms and/or stereos. Often times the drain is so minute that you would not be able to detect the voltage drop in the usual manner by pulling all your fuses out and slowly watching the voltage on a meter. I went through this nightmare for several years on another car (replacing about 2 batteries during that time) that I finally took it into a specialty automotive electrical shop. They found the problem in about 1 hr of labor and the problem has never returned.

theiceman

I think a normal amount of current drain would be in the area of 15millamps or so. This should power the on board clock and maybe even the memmory of an aftermarket stereo. But if you have an aftermarket connected to the constant power and for example the thing is trying to eject a CD and is jammed , that will definitely kill it. Poor design of the thing to but that extra info you gave us is very important .. start there .

JBrown

If you set your multi meter right, you will definetly see the draw disapear when you remove the fuse. If your meter is accurate. That is how I find draws all the time. You are not looking for a voltage drop buy the way. You are looking for an amp draw. That was your problem. removeing fuses should not really change the voltage that much. You will see changes in amps when you remove the right fuse.

JBrown

iceman is right. It is also very low readings ( milliamps). Aftermarket changers do get constant power and are prone to go bad. Do the draw test with the changer in and remove it see if your amps drop.

ron mcatee

My radio like most has a secondary circuit that allows the internals to memorize time, requencies, etc. Over a period of 2 days the battery would run down. I found the secondary circuit in the radio had shorted to the primary circuit and allowed it to be a primary circuit all the time. Repcaed the radion and now i can go several weeks with no problems.

Brads911sc

I can let my car sit for two months with a five year old Interstate battery and it starts everytime with no issues. Dont mean to disagree with others... but if your battery is draining down in 7-10 days, you have a problem and that would not be considered normal...

theiceman

I think Brad you are in General agreement with everyone. I have an interstate too and it can go forever practically. I just know the optima i think they are called are a light dry cell and I just was not sure of the capacity of such a battery. Those who have them will know for sure. I think we all agree he has some sort of issue, once he posts what kind of drain he is getting we will know for sure.
In Rons case for example it sounds like he was powering his amps as well as his memmory circuit which will kill th ebattery for sure. I might actually check the drain in mine just for reference and for future posters to search. I have an SC with an aftermarket MP3 player , but that is all.

Brads911sc

Agree Ice. Seems like alot of optima users run into this sensitivity issue.

JBrown

I would not say optimas are sensitive but I have seen some go bad. If the battery is good, that is not his issue. A red or yellow top will hold power just as long if not longer than a standard battery. What no one is thinking about is the chargeing system. That is the easiest test. If the alternator is old it could not be charging to full capacity and that would cause the isssue. If that is ok, then he has an excess current draw. I have 2 porsches . 944 turbo and my 911sc turboed. I have all kinds of equipment on them, stereo systems, remote starts, alarm, amps, handsfree kits and I have no problems with draw. If I was to have a problem the first place I would look is at the aftermarket stuff but that does not mean it definetlly is the aftermarket equip. that is why I say to ck system in the order I say and you will find the problem. I have been doing car audio and electric for 27yrs and it is not that difficult to find it. So many people over look the basics and just start to ripp thing out. Good battery and good charging system is the first thing to test. If that is all good do draw test and see what you have for a draw. I do agree that a specilist in this feild would find it within 15 min I bet. John

whalebird

You should set your multimeter on AMPS when draw testing. Also you want to connect the battery post and battery ground cable to the multimeter before you brake the connection between the post/terminal. It is cumbersome to do it correctly. The idea is to not disconnect the battery before you attach your meter. When you brake the connection before putting the meter in line, it is possible to deactivate the culprit and it dosent wake up until you start the car again-thus reconnecting the battery terminal.
I have found that an automatic antenna will often cause a draw when it goes down and somehow stays engaged. Very common source of a draw. Aftermarket stuff is next most common.