Dead battery
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,466
Likes: 43
From: Auburn MA
Dead battery
I have a 94 coupe and it is currently being stored outside in MA. Now for some reason if it sits for 2 weeks or more the battery is dead to the point where it wont turn over it will just make the clicking noises. I just put a brand new yellow top Optima battery in it this year... So is this normal that the PKE or the security system is this much of a drain on the battery or is there something wrong with this car. I heard before that a "sticking Bose relay switch" which from what i heard is under the compartment behind the pass seat could be a culprit... If thats true where can i get one.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You must not visit C4 tech much. I have posted over and over and over about the care and feeding of lead acid batteries and about excessive leakage current. Lets do this one more time.
With normal leakage current you should be able to leave your car sit for 2 weeks and it should start. This leads me to believe that you have excess leakage current. GM says leakage must not exceed 50 milliamps. My 87 draws 27 ma. First, at night, check the underhood lights, vanity mirror lights, door map lights, center console light, do you have a radar detector, aftermarket alarm, radio, or audio amplifier? Check em. You need to remove the negative cable and place an ammeter in series between the neg cable and the neg batt terminal to measure leakage current. When the courtesy lights time out (they draw several amps), switch down your test meter to a scale where you can read the leakage current. Pull the courtesy light fuse so they don't stay on with the passenger door open and start removing fuses one at a time while watching the ammeter, this will tell you what circuit is drawing current. I believe on the 94 there are several large fuses near the battery, you should pull those too. I don't know where they are on a 94, but there are ciruits that use fusible links and those should be disconnected one at a time too to find the leakage path.
Lead acid batteries self discharge up to 1% each day even disconnected and their plates collect lead sulphate which is an insulator. A fully sulphated battery is a door stop. If you know your car is going to be sitting for more than 4 weeks, you should arrange to charge the battery periodically so it doesn't discharge and sulphate. The best way is to buy a battery tender which keeps the battery up without overcharging it. A trickle charger may or may not be safe depending on how it was designed, battery tenders are designed not to overcharge batteries.
With normal leakage current you should be able to leave your car sit for 2 weeks and it should start. This leads me to believe that you have excess leakage current. GM says leakage must not exceed 50 milliamps. My 87 draws 27 ma. First, at night, check the underhood lights, vanity mirror lights, door map lights, center console light, do you have a radar detector, aftermarket alarm, radio, or audio amplifier? Check em. You need to remove the negative cable and place an ammeter in series between the neg cable and the neg batt terminal to measure leakage current. When the courtesy lights time out (they draw several amps), switch down your test meter to a scale where you can read the leakage current. Pull the courtesy light fuse so they don't stay on with the passenger door open and start removing fuses one at a time while watching the ammeter, this will tell you what circuit is drawing current. I believe on the 94 there are several large fuses near the battery, you should pull those too. I don't know where they are on a 94, but there are ciruits that use fusible links and those should be disconnected one at a time too to find the leakage path.
Lead acid batteries self discharge up to 1% each day even disconnected and their plates collect lead sulphate which is an insulator. A fully sulphated battery is a door stop. If you know your car is going to be sitting for more than 4 weeks, you should arrange to charge the battery periodically so it doesn't discharge and sulphate. The best way is to buy a battery tender which keeps the battery up without overcharging it. A trickle charger may or may not be safe depending on how it was designed, battery tenders are designed not to overcharge batteries.
