The battery in my 78 will go flat in 4-5 days. I have had it checked out and charged and it will spin the starter with out any problems. I think it probably has a drain somewhere. What would be the most likely area to check? Thanks!

 

Just start by sticking a meter on it to measure the current from the battery and pull fuses to narrow it down.

Just incase you're not familiar with measuring current you need to have your meter in series not parallel.

 

First thing you can verify is that the factory anti theft system is disengaged..On the 78, use the door locking key on driver's side lock and turn key all the way counterclockwise.Then turn the key all the way clockwise..Then turn the key back counterclockwise to the 12:00 position and remove the key.THAT is the disengaged position for the funky antitheft system that came on the 78(I have one..)
The antitheft system is pretty intricate and prone to problems..door switches, t top switches, hood etc..IF you have the owners manual verify the fuse locations for components..
with battery fully charged..disconnnect negative bat term and attach you meter to that cable and bat post..HAVE METER SET ON ampereage..See what meter shows for current draw with everything off but the electric clock..Door switches closed for off interior lights..
After disengageing antitheft system for sure..current draw should be very low like 40 miliamps..
IF it's still high, you then pull one fuse at a time until you identify the offending circuit and narrow the list of guilty components-wireing....When you pull the fuse on the offending circuit that has a parasitical current draw, your meter will show the normal small miliamp draw that is from the system and electric clock only..A qualified auto battery electric shop can do this for a very nominal fee and determine what might be the problem and what the cure is to be also..Jim

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You Tube is your friend. If you want to learn just about anything you will usually find a video on there with good information.

 

If you've got a glove box light, make sure it's going off. If you've got an aftermarket radio with clock and station memory, disconnect the power for a while and see if that stops the drain. After that, you'll need to measure and pull fuses or wires. I'd also disconnect the red wire to the alternator and see if you might have a leaky diode in the rectifier circuit.

 

I have an aftermarket radio/cd sound system as well as power antenna on mine..I shut the entire system down when I park-leave the car.Power antenna goes down and all that potential current draw eliminated.Jim
I occasionally use a small Battery Tender jr when I leave the car for a few days in the garage..It has an accessory that allows me to plug it into the cigarette lighter receptacle( which is hot when ALL power is off..)
The battery tender insures your battery is always properly and fully charged...IF you have some hidden current drawdown of any consequence , the battery tender will NEVER show the solid green light indicating battery is fuly charged..Jim
Did you ever verify that the factory alarm circuit was disengaged?

 

I haven't had a chance to test anything yet. I charged the battery and it is hot now. Before when I hooked the bat up there was a fair arc, which I thought was the overhead light and relay. I will check the amp draw between the neg cable and battery and do the fuse pulling test Sunday. Thanks!

 

hmmm..the arc isn't a good sign..but is an indicator of something in the system can't recll just what..jim
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Hooked up an amp meter between battery and ground cable and checked draw after courtesy light went off. Measured about .20 amp. When the door lock was turned to the right, the draw stopped. I unplugged the connector to the theft relay, and the draw stopped.

 

Great..That factory alartm system has so many components that can draw power even if the horns aren't honking.Disengage it. don't turn that driver's side lock to the Left..ever..I lock the passenger's door with the internal button..and drivers side the same way..TO unlock, driver's side door key lock to the Right only..Jim

 

parasitic draws can be a pita to find, use a good meter on each circuit to start. pull fuses to narrow it down some. obviously an electric clock and a modern radio with memory are going to be drawing.

easy solution is a manual battery disconnect, which I have on all 3 of my vette's...that said, the battery is probably in not too good a shape if it keeps being drained without charging every 3-4 days. not good for a non deep-cycle to be drained like that...

 

My stereo was causing mine. Switched to an ignition circuit verses a battery. Problem solved.

 

Hopefully disconnecting the theft relay will take care of it. A battery disconnect may be a good idea.

 

What do you mean an ignition circuit?

 

I think he means powered on with key on, not constant battery. there is usually a terminal in the fuse box labeled "Ign" which is a keyed hot.