I hope to work on this in a few hours, so your quick help is appreciated.

The BlueDemon is slightly sick and we hope maybe you guys can help. The owner has been out of town for a week, now when he gets back to the car the battery is dead. As for the battery it is the third one he has had in the car in a very short period of time. I think he has something that is draining it. To prove this I want to connect a multimeter inline with the battery and see what kind of current draw it has when the car is off.

For those of you who have done this, how should I go about this? I was thinking to disconnect one of the battery cables (which one?) and simply connect the multimeter between the disconnected cable and the battery. Of course I would need to charge the battery first or I won't be doing any good. My major question is what kind of current drain is normal? I know there has to be something to maintain the radio and such, but certainly not enough to drain the battery that quickly.

The car has done this before, many times. It's just one of those things where if you drive it every day you don't have any trouble out of it so I know the charging system works. It may be good enough for him to leave it that way, but I don't like it. We are going to be adding an MSD 6a ignition and an additional fuel pump, given that extra load I want to make sure that his electrical system can handle it.

One more thing, how would you go about tracking something like that down? I thought about if there was a large drain on the battery we could start pulling fuses and see if one of them gets rid of the drain. If so we know which circuit it's in, but what if none of the fuses kill it?

Thanks guys

 

Ok, yes, first charge the battery, that should take several hours. When you are satisified it is charged, disconnect the negative cable (it doesn't really matter which one, but the neg should be easier). Next, take your multimeter, set it to it's highest AMPS setting (first, we'll back it down in a minute), and connect it in SERIES with the negative cable and negative post of the battery. Put the positive lead of the meter to the cable and the negative lead to the post. MAKE SURE IT IS IN AMPERE MODE! Now, as soon as you connect the last lead of the meter, note the current draw. If it is over 1 amp (you may have to adjust the scale on the meter), you definatley have a higher than normal current draw. The easiest way to diagnose it at this point is to pull the fuses one at a time and see if you can lower the draw signifigantly. It should go without saying, but DO NOT ATTEMPT TO START THE CAR WITH THE METER IN SERIES!! Most meters can only handle up to about 10 amps, the starter will suck about 300 amps (peak instant). Buh-buy meter if you try that!

Good luck! Let us know what you find!

 

Sounds good man, I just wanted to double check. Thanks for your quick response. I wasn't going to start it, but wouldn't it be fun to watch the meter fry, especially if it's not yours :reddevil

 

Is there an alarm system on it? I've got one with all kinds of monitoring capability (e.g. motion detector) and my battery does the same thing. If I don't drive it for close to 2 weeks, I'll come out to a dead battery. I think I'm drawing 7 amps which I'm not comfortable with.

When you do your amp draw test, make sure your doors are closed and unplug the "under the hood" lights. This will lower the electric draw for your test. Basically, make sure the car is sitting with everything OFF like it would overnight.

I need to pull the fuses as mentioned above and see if something else is 'helping' drain my battery, too. Keep us posted.

 

That's a good point, make sure the under hood lights are unplugged, those will pull a few amps themselves. Speaking of underhood lights, make sure they actually turn off when you close the hood, there's been stories where the mecury switch is defective and the lights don't shut off.

 

7 amps and it lasts 2 weeks? My friend must be pulling like 30, it'll actually go dead in like 2 days, it just happened to be a week between attempts this time. I wouldn't be comfortable with that 7 either, sounds like a pretty healthy drain to me.

 

Ok answer me this. The car is a 95 Z-28. I know it doesn't have underhood lights now, but it has an aftermarket hood. Should it have had such lights originally? If so that may be the problem, knowing the owner he may have just left them hanging somewhere.

 

He might not be pulling extremely excessive amps, but if he lets it drain to near dead *a lot* the battery will never be able to charge to reach 'full charge'. So, in essence, his times between dead battery is lessened - maybe down to the 2 days you're seeing.

 

Possibly, but he bought a new battery when he thought he would be able to start the car after his rebuild, so we had some issues and the car didn't start. He put a charger on it and let it do it's thing for several hours, that should be more than enough for a new battery to reach full charge. Even then it was dead in a matter of days.

 

92shawnster is right about the underhood lights, on my 87 I could see them turn off,but, they would sometimes come back on with the hood down. no problems after I unhooked them.

 

keep the meter hooked up and start unplugging fuses and circuit breakers. Youll find weird drains. I had a defective power window switch draining mine when ignition was off.

 

You want to see under 50mA draw a 300mA (0.3 amps) will kill a battery in about 3 days 7amps probably over night. If the battery goes dead in 2 days be looking for a good draw like lights staying on maybe glove box light things like that.

David Fulcher

 

Hey David, Happy New Year. Good to see you back on the forum. Hope all is well with you and yours!!!

Pete

 

Thanks Pete, I have just not had the time to spend but we have been a little slow here at work so I have been able to get back at it. The baby and family are doing fine thanks for asking but it does keep me from going on line at home, I would also like to wish you a happy new year also maybe I will be able to spend a little more time her this next year.

David Fulcher

 

Depending on how deeply discharged a battery is, you cannot charge one back up in 2 hours. Full recharge takes 4 days. But....several hours of charging will allow a couple of cranks to restart, then the alternator will be putting out high current. A fully recharged battery has terminal volts of 13.2 volts.