unplug your alternator. 5 amps is huge.
87 C4 Electrical Drain
Intermediate
Joined: May 2007
Posts: 44
Likes: 0
From: Racine Wi
Are you sure? 5 amps
Are you 100% sure you have a 5 amp draw? A light bulb in a glove box draws about 1 amp and that will take out a battery over night. 5 amps will wipe a battery in a couple of hours. Check your meter and be sure. I could see if you had .5 amps you may last a couple of days. How old is the battery? Some draw will be there even with all the fuses pulled. Some items get battery power through fusible links or isolated fuse blocks. I belive there is a junction next to the battery for multiple links. Disconnect there and check again. Adding one at a time until the draw comes back works better for me. Good luck.
Le Mans Master
Joined: Jul 2007
Posts: 5,356
Likes: 2
From: No HOA, New Hampshire
Cruise-In X Veteran
St. Jude Donor '09
One of the things I noticed in Helms Manual Electrical section is how many devices' wires are "Hot All The Time" while fused or switched wires are connected to the same device. 5 amp draw is a serious problem. Think about what is somewhat active when the ignition is off, key out and unplug them one at a time. I am waiting for my FSM but as an electrician I would start at the remote positive terminal that has at least 6 red wires connected to it. If one of them eliminate the draw follow that part of the harness to individual devices to narrow down the search. (Luck is 51% of the expert technician)
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Behind the battery is a jump start bolt with 8 red wires. Remove the nut and remove the wires one at a time while watching your ammeter. 5 amps could be the courtesy lights, have you waited for them to time out? Also, you should check at night, battery connected, for the underhood lights, vanity mirror lights, door panel lights, rearview mirror map light. Don't leave your key in the ign as it keeps the theft alarm circuit on. Do you have a radar detector, CB transceiver, aftermarket alarm or audio amp or radio? Check em. Your battery, disconnected, should hold constant voltage overnight UNLESS you measured the voltage after running the engine because battery voltage right after charging, falls. It sounds to me like your battery has internal leakage current and is self discharging (although 5 amps is WAY TOO much leakage current). GM says leakage current should not exceed 50 milliamps. All lead acid batteries self discharge but usually less than 1% each day. Battery capacity can be determined by the no load battery voltage: 12.0 volts and lower, discharged, 12.9 volts and higher, fully charged. A 1% discharge is about .01 volts.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by pkazsr
I would start at the remote positive terminal that has at least 6 red wires connected to it. If one of them eliminate the draw follow that part of the harness to individual devices to narrow down the search.
Originally Posted by jfb
Behind the battery is a jump start bolt with 8 red wires. Remove the nut and remove the wires one at a time while watching your ammeter.
Originally Posted by jfb
Your battery, disconnected, should hold constant voltage overnight UNLESS you measured the voltage after running the engine because battery voltage right after charging, falls. It sounds to me like your battery has internal leakage current and is self discharging (although 5 amps is WAY TOO much leakage current).
Originally Posted by 8VETTE7 Post #2
Any suggestions on how I proceed or where I look from here???
Originally Posted by CFI-EFI Posr #3
To the fusible links.
Last edited by CFI-EFI; Sep 18, 2007 at 02:42 PM.
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
Assuming this is an '87, you need to make sure the interior lights time out - about a 3 amp draw. When you disconnect and then reconnect (even though you're using your meter), the interior lights usually pop on. They will stay on until the Delay Module opens and turns them off - so wait until that happens and then check your reading. Note - depending on the scale you're using with a DVM it's probably going to overrange until this happen. Also, make sure the underhood lamps are off - disconnect them. Then, after you get a reading with EVERYTHING off, you can reconnect the hood lamps and gently lower the hood with your meter still hooked up. That will ruleout a stuck switch on one of the hood lamps (though you should be able to see those lamps turnoff as you lower the hood).
Last edited by SunCr; Sep 18, 2007 at 07:05 PM.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
There isn't an ammeter made in the universe that can measure the battery internal leakage current because that current does not flow out of the battery terminals!!!!! You should still measure the EXTERNAL leakage current and it should not exceed 50 milliamps (GM's spec)!!!
Instructor
Joined: Jul 2007
Posts: 222
Likes: 0
From: Toronto(Don Mills) Ontario
A few years back, out of idle curiosity, I checked the 'dormant' current draw on my L86 Coupe. Was 18 Milliamps(18 one-thousanth of an Amp), which I gather is normal for my year, and probably the same for 87's? Cheers.
