Topic: Electrical Issue - Battery drains when parked/engine off

[weezer4rock]

1996 Mustang GT convertible.  When parked in my garage for too many days the battery will be dead.  Obviously something is draining the battery but I'm miffed!  I disconnected the negative battery cable and inserted my DMM in series.  There is zero amperage reading on my DMM!  I have a 10amp and 2amp setting.  No reading on either.

Note: I am positive the battery had a charge when running this test because I had just driven it.  AND is cranked right up after doing the test.

If anyone has other testing or troubleshooting ideas PLEASE share.  I think with the right idea I'd be able to solve the problem myself. 

Thanks to all.

[midlife]

It is impossible for there to be perfectly zero current; there has to be some draw for the radio memory at a minimum.  I believe your DMM is faulty, fuses blown, or you're not using it correctly. 

[Bob Gaines]

1996 Mustang GT convertible.  When parked in my garage for too many days the battery will be dead.  Obviously something is draining the battery but I'm miffed!  I disconnected the negative battery cable and inserted my DMM in series.  There is zero amperage reading on my DMM!  I have a 10amp and 2amp setting.  No reading on either.

Note: I am positive the battery had a charge when running this test because I had just driven it.  AND is cranked right up after doing the test.

If anyone has other testing or troubleshooting ideas PLEASE share.  I think with the right idea I'd be able to solve the problem myself. 

Thanks to all.

If the battery went "dead" which is all of the way then it is probably the battery at this point instead of a drain in the system somewhere. Batteries only have a certain life time. Some will last 3 or 4 years others will last more . If a battery goes dead it basically cuts the life in half. If it dies twice then half of that half and so on.  If that happens more then a couple times there is not much time left to be a viable battery and you are living on borrowed time before it doesn't hold a charge long if at all .It also has to do with how long the battery is left dead also the longer it is left dead the harder it is on the battery life. I get the impression from your post that your battery has died more then once. You may be at the point where the battery is beyond the point of no return.  There may have been a drain on the system that started the domino effect but if the end result was the battery went dead then that can only happen a few times before it ruins the battery permanently. I have had a battery not hold a charge after going dead (left the lights on and battery was left dead for a week) once. Fortunately it was still under warranty and I was able to turn it back in for another . The auto parts store didn't even check anything. 

[Bob Gaines]

Maybe not a 1996 vintage car but the cars of the last 15 years or so have so much of the electronics going on in the background when the car is sitting idle that many if they sit more then a month without running will drain the battery down to the point that they will not start. I can remember when I  bought my Ford GT in 2006 that it came with a float charge to keep the battery viable because I guess Ford knew that many times they were going to be stored for long periods. 

[weezer4rock]

It is impossible for there to be perfectly zero current; there has to be some draw for the radio memory at a minimum.  I believe your DMM is faulty, fuses blown, or you're not using it correctly.

Interesting... i do no deny that user error is the most likely source  . 

I'll start by checking the fuses in the meter and go from there.

[weezer4rock]

If the battery went "dead" which is all of the way then it is probably the battery at this point instead of a drain in the system somewhere. Batteries only have a certain life time. Some will last 3 or 4 years others will last more . If a battery goes dead it basically cuts the life in half. If it dies twice then half of that half and so on.  If that happens more then a couple times there is not much time left to be a viable battery and you are living on borrowed time before it doesn't hold a charge long if at all .It also has to do with how long the battery is left dead also the longer it is left dead the harder it is on the battery life. I get the impression from your post that your battery has died more then once. You may be at the point where the battery is beyond the point of no return.  There may have been a drain on the system that started the domino effect but if the end result was the battery went dead then that can only happen a few times before it ruins the battery permanently. I have had a battery not hold a charge after going dead (left the lights on and battery was left dead for a week) once. Fortunately it was still under warranty and I was able to turn it back in for another . The auto parts store didn't even check anything.

I do not disagree on principle but I don't think this applies.  I've been through several batteries with this issue and the one there now should be ok to at least show a current draw.

[Bob Gaines]

I do not disagree on principle but I don't think this applies.  I've been through several batteries with this issue and the one there now should be ok to at least show a current draw.

If you have been through several batteries with the same issue then you have some kind of battery drain. The domino effect with what the problem causes each battery when it goes dead will be exactly the same. I was trying to explain that even if you find the drain that initially caused the problem that the battery life and or holding a charge capacity could already be irreversibly compromised.

[Bob Gaines]

If you have been through several batteries with the same issue then you have some kind of battery drain. The domino effect with what the problem causes each battery when it goes dead will be exactly the same. I was trying to explain that even if you find the drain that initially caused the problem that the battery life and or holding a charge capacity could already be irreversibly compromised.

I should add that the battery condition will depend on how many times the battery is allowed to go dead before you find the solution to your battery drain.

[weezer4rock]

If you have been through several batteries with the same issue then you have some kind of battery drain. The domino effect with what the problem causes each battery when it goes dead will be exactly the same. I was trying to explain that even if you find the drain that initially caused the problem that the battery life and or holding a charge capacity could already be irreversibly compromised.

got ya

[midlife]

Here's my standard statement that I provide every customer for finding a parasitic draw before hooking up a battery (assuming they are installing wiring):

 Physically install the underdash harness with fuses.  Connect all underhood and taillight harnesses.
 When ready to check out the harness, close all doors, turn off all lights, accessories, etc.  Make sure both battery connectors are disconnected.  Connect the positive battery cable to the starter solenoid.  Leave the negative terminal disconnected from the battery.  Then use a digital volt meter to measure the current draw across the battery.  Place one probe of the DVM on the negative battery cable terminal, and the other probe on the negative battery post.  Be sure that the DVM is set to amps, DC.  If there are no shorts in the wiring connections, the reading should be on the order of 30 milliamps or less.  Anything above 1 amp indicates some accessory is on; readings above 10 amps (may blow the fuse on the DVM) indicates a dead short.
 If you have a short, disconnect all other wiring from the starter solenoid post where the battery connects and re-measure the current.  If current drops, the source is the underdash wiring harness or the harness from the starter solenoid to the firewall.  Reconnect the wiring to the starter post and then disconnect the underhood harness from the firewall and test again to isolate the source of the short. 
If the short is not in the underhood or underdash harness, the problem lies in the alternator or voltage regulator.  Disconnect each of these in turn to isolate the source.
 If the short or high current comes from the underdash region, keep the battery negative side disconnected and remove one fuse at a time.  Measure the current as above.  If you now see low current, there is either a short or an item on that particular fuse circuit is on.  Turn off that item and continue checking.
 Eventually, you’ll have low current readings with all fuses installed and all wiring connected.  At that time, and only at that time, is it safe to connect the negative battery cable to the battery.
 This series of tests checks all of the battery directly powered systems.  To check the Accessory systems, now repeat all of the tests above with the ignition key in the ACC position.  The current with the key in the ACC position may be up to 1 amp or so.  When all of the tests are done and no anomalous current is noted, at that time, and only at that time, is it safe to connect the negative battery cable to the battery.
 

[Bossbill]

This fix applies if you have the Mach 460 stereo with CD player.

My 96 GT with the high end Mach 460 system had something odd go wrong inside the CD player and it stayed on when parked with engine off and drained batteries with regularity.

If so equipped, disconnect it and see if that works for you.

[weezer4rock]

I do have the Mach... nice tip... I'll try that first.

[weezer4rock]

This fix applies if you have the Mach 460 stereo with CD player.

My 96 GT with the high end Mach 460 system had something odd go wrong inside the CD player and it stayed on when parked with engine off and drained batteries with regularity.

If so equipped, disconnect it and see if that works for you.

I removed 25amp fuse from box inside engine bay and 15 amp fuse under dash that relates to the radio.  I'll report if this resolves it.