C4 Sits = Dead Battery
Thread Starter
Instructor
Joined: Apr 2010
Posts: 215
Likes: 0
From: Lakeland FL
C4 Sits = Dead Battery
I have a buddy that has a 1986 C4. He bought it a few years ago and it has spent much of it's life (so far) with him sitting in his garage. He's pretty busy with a new company that he's started so I have to cut him some slack....
He has a lingering problem.....
If the car sits.....the battery dies..... He has recently replaced the battery, drove it home, parked it......and a few days later......dead battery.
Is there a common problem or direction I can point him in? We both fund our hobbies with our full time jobs.....computer network engineering.
Thanks....
He has a lingering problem.....
If the car sits.....the battery dies..... He has recently replaced the battery, drove it home, parked it......and a few days later......dead battery.
Is there a common problem or direction I can point him in? We both fund our hobbies with our full time jobs.....computer network engineering.
Thanks....
Instructor
Joined: Nov 2009
Posts: 162
Likes: 0
From: Houston Texas
I have the same problem, one week does it for me. But the previous owner routed some wires from the battery/fuse area to a custom sound system and I'm guessing thats leeching power even while its off.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Sounds like an open circuit somewhere that is draining the battery. It could be something as simple as the light in the console lid staying on even if the lid appears to be closed. Another possibility is an underhood light that has a bad mercury switch. Both of these can easily be checked in a dark garage.
First, charge the battery. Then disconnect the negative battery cable and connect a DVM inline between the cable and negative terminal. Set the DVM to millamps (mA) and record the value. At the fuse panel, start by removing one fuse at a time to see if the reading drops.
When a fuse is pulled and the displayed value drops, that indicates there is something in that circuit drawing power. Sometimes it's a bad relay, or possibly a short to ground.
If your buddy doesn not have a FSM or Factory Service Manual, it should be the first thing to get if he intends to do any work on the car himself. This will be a 2-book set and one book is devoted to the electrical system and includes wiring schematics and electrical troubleshooting procedures for the entire car. They can be found on occasion in the C4 Parts For Sale section or on fleabay.
First, charge the battery. Then disconnect the negative battery cable and connect a DVM inline between the cable and negative terminal. Set the DVM to millamps (mA) and record the value. At the fuse panel, start by removing one fuse at a time to see if the reading drops.
When a fuse is pulled and the displayed value drops, that indicates there is something in that circuit drawing power. Sometimes it's a bad relay, or possibly a short to ground.
If your buddy doesn not have a FSM or Factory Service Manual, it should be the first thing to get if he intends to do any work on the car himself. This will be a 2-book set and one book is devoted to the electrical system and includes wiring schematics and electrical troubleshooting procedures for the entire car. They can be found on occasion in the C4 Parts For Sale section or on fleabay.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Sounds like an open circuit somewhere that is draining the battery. It could be something as simple as the light in the console lid staying on even if the lid appears to be closed. Another possibility is an underhood light that has a bad mercury switch. Both of these can easily be checked in a dark garage.
First, charge the battery. Then disconnect the negative battery cable and connect a DVM inline between the cable and negative terminal. Set the DVM to millamps (mA) and record the value. At the fuse panel, start by removing one fuse at a time to see if the reading drops.
When a fuse is pulled and the displayed value drops, that indicates there is something in that circuit drawing power. Sometimes it's a bad relay, or possibly a short to ground.
If your buddy doesn not have a FSM or Factory Service Manual, it should be the first thing to get if he intends to do any work on the car himself. This will be a 2-book set and one book is devoted to the electrical system and includes wiring schematics and electrical troubleshooting procedures for the entire car. They can be found on occasion in the C4 Parts For Sale section or on fleabay.
First, charge the battery. Then disconnect the negative battery cable and connect a DVM inline between the cable and negative terminal. Set the DVM to millamps (mA) and record the value. At the fuse panel, start by removing one fuse at a time to see if the reading drops.
When a fuse is pulled and the displayed value drops, that indicates there is something in that circuit drawing power. Sometimes it's a bad relay, or possibly a short to ground.
If your buddy doesn not have a FSM or Factory Service Manual, it should be the first thing to get if he intends to do any work on the car himself. This will be a 2-book set and one book is devoted to the electrical system and includes wiring schematics and electrical troubleshooting procedures for the entire car. They can be found on occasion in the C4 Parts For Sale section or on fleabay.
First, lead acid batteries self discharge even disconnected. Never leave a battery sit for long periods (4+wks) because the plates collect lead sulfate and ruin the battery. Cars that sit for long periods should have a battery tender connected to them to keep the battery charged up. Batteries kept charged will have a normal life, ones that get totally discharged over and over have a short life.
Disconnect the negative battery terminal and measure the leakage current, GM says it should not exceed 50 milliamps. Pull the courtesy light fuse so the courtesy lights don't come on when you connect your ammeter. My 87 draws 27 ma. and I don't have any battery problems.
Also, at night check for the underhood lights, vanity mirror lights, door map lights, console light. Do you have a CB, GPS, radar detector, aftermarket alarm or radio or audio amplifier? Check em. Don't leave your ign key in the ign because it keeps the antitheft circuit on.
Burning Brakes
Joined: Jul 2003
Posts: 811
Likes: 0
From: Nashville TN
Are the keys staying in the ignition? Sounds odd, but once I saw a similar thread when I was having the same issue about drawing current perhaps from the security sys? No clue, anyways....problem was solved once I started leaving the keys in a smarter place.
Pro
Joined: Jul 2006
Posts: 635
Likes: 1
I would also test the alt., if you have a bad diode it will drain battery just like that. You could test by looking for voltage drain at alt. wires as stated before or a lot of auto parts stores will test it for you free.
Le Mans Master
Joined: Feb 1999
Posts: 6,470
Likes: 2
From: levittown pa. usa Even a bad day with my `Vette, is better than a good day at work
St. Jude Donor '10
All of my Vettes would go dead if I let them sit for a couple of weeks. Thats why I invested in a couple of battery tenders. 
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Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
A malfunctioning digital dash will drain the battery too. A buddy of mine had a draining problem on his 85 and, rather than having the dash repaired, he just installed a cut off switch right at the battery.
The switch he used is like the ones you find mounted to the rear of many drag cars.
You could try the fuse pulling trick (with a volt meter attached to the battery) to see which fuse causes a voltage increase when it's pulled.
Jake
The switch he used is like the ones you find mounted to the rear of many drag cars.
You could try the fuse pulling trick (with a volt meter attached to the battery) to see which fuse causes a voltage increase when it's pulled.
Jake
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
A malfunctioning digital dash will drain the battery too. A buddy of mine had a draining problem on his 85 and, rather than having the dash repaired, he just installed a cut off switch right at the battery.
The switch he used is like the ones you find mounted to the rear of many drag cars.
You could try the fuse pulling trick (with a volt meter attached to the battery) to see which fuse causes a voltage increase when it's pulled.
Jake
The switch he used is like the ones you find mounted to the rear of many drag cars.
You could try the fuse pulling trick (with a volt meter attached to the battery) to see which fuse causes a voltage increase when it's pulled.
Jake
DON'T USE A VOLTMETER.
Burning Brakes
Joined: Jun 2008
Posts: 895
Likes: 3
From: toledo ohio
i had a similar problem in my 85, it was the interior courtesy light timer. i couldnt recognize it right away because the po had removed all of the interior light bulbs, but when i replaced them i noticed they never turned off. timer was bad and was draining battery. wilcox is now selling a new timer board, cheapest and best solution you can find for this problem. hope that helps. good luck!
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
You find which circuit has excessive leakage current pulliing fuses when you connect a milliammeter, or ammeter in series with the battery!!! You learn nothing if you use a voltmeter because modern voltmeters are so high impedance that they will indicate the battery voltage all the time even if you pull a fuse on a circuit with high leakage current!
DON'T USE A VOLTMETER.
DON'T USE A VOLTMETER.
Remind yourself, this is not a competition but, instead, is our attempts to help a fellow member.
All of what you wrote would be fine except for the fact that it's how Alfred found it was his dash pulling down his battery, by using a volt meter.
Whatever works for Kirt is my goal. Not get involved in a "My advice is better than your advice" waste of time exercise.
Jake
Pro
Joined: Jun 2005
Posts: 584
Likes: 62
From: USA
i put in a battery disconnect switch on mine after going through a relatively fresh battery. now i pop the hood and disconnect the battery after every "session".
since the Bose radio is long-since dead (inoperative), I don't have to worry bout losing the radio stations, or time-of-day.
since the Bose radio is long-since dead (inoperative), I don't have to worry bout losing the radio stations, or time-of-day.
Le Mans Master
Joined: May 1999
Posts: 6,520
Likes: 1,306
From: Windermere FL
Our Vettes are notorious for this. Simple solution. Get a Battery Tender (sold at most auto parts store) and slice it into a cigarette adapter. You plug it into the lighter socket when it is parked and it is super easy to connect and disconnect. Plus your battery will last much, muck longer.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You seem to be very emphatic in your advice, with all the exclamation points and ALL CAPS. As if there's absolutely no chance using a volt meter would work. In my opinion, the added emphasis is unnecessary and misplaced.
Remind yourself, this is not a competition but, instead, is our attempts to help a fellow member.
All of what you wrote would be fine except for the fact that it's how Alfred found it was his dash pulling down his battery, by using a volt meter.
Whatever works for Kirt is my goal. Not get involved in a "My advice is better than your advice" waste of time exercise.
Jake
Remind yourself, this is not a competition but, instead, is our attempts to help a fellow member.
All of what you wrote would be fine except for the fact that it's how Alfred found it was his dash pulling down his battery, by using a volt meter.
Whatever works for Kirt is my goal. Not get involved in a "My advice is better than your advice" waste of time exercise.
Jake
