MENU Subscribe to a Magazine
  • Sign in
  • Join

Subscribe to Print or Digital! Save up to 83%

Magazine Muscle Mustangs & Fast Fords
Magazine Mustang Monthly
Magazine 5.0 Mustang & Super Fords
Magazine Modified Mustangs & Fords
  • Print Subscriptions
  • Digital Subscriptions
  • Gift Subscriptions
  • Subscriber Services
  • Back Issues
  • Personalized Cover
  • Subscribe to a Magazine
Item Posts    Sort Order

Charging Problem ?

 
ptomb3
New User
Posts: 3
Joined: 06/12
Posted: 06/22/12 09:26 AM

Confused We have a modified 2003 GT (5.0 crate stroker, kenne bell twinscrew, etc.)  It has run great since the modifications in 2004, but for the past year has developed an electrical problem. It will be starting/running great, then the next time I try to get in it, the door locks won't even open ... battery will be at 9 or 10 V.  It is driven 3 or 4 times/week, but it did sit for about a year without much driving just before the problem started. We've been through 2 battery replacements ... will be great for 3 months or so, then same ole same old. I can charge the battery, and it will be OK again ... for a while.  My son and I have checked alternator charging (14.4 V to 14.8 V), and have looked for current leaks 'till we're blue in the face and found nothing.  I know it sounds like the system is just running off the battery until it gets too low to run it ... but can't figure out why. If it is an alternator problem, it is intermittent, and doesn't show when we are checking it.  We are just before taking it to a shop (a little emabarassing, since my son and I are both engineers and he pretty much built it)!  Any ideas that we may have missed? Thanks. TomB  

Post Reply
MustangMan
Moderator
Posts: 259
Joined: 08/11
Posted: 06/25/12 06:45 AM

Does the car have an aftermarket alarm or just the factory keyless entry and PATS system? How did you check for "current leaks" (I like that term! LOL). Generally you place a volt-meter or test light between the battery terminal and cable (with cable removed) to check for any accessive current draw. Start pulling fuses until the draw dissapears and then you can focus your diagnosis on that area. Watch for false positives like the dash fuse (anti-theft). Also, does it have an aftermarket audio system or head unit in it? I've seen those go bad and pull excessive amperage.

HTH...
Mark
.  
Mark Houlahan
Brand Manager
Mustang Monthly Magazine

1965 FFR Roadster 427W/TKO-600 5-speed
1966 Mustang 289-4V/C4 Auto
1968 Mustang 4.6L Three-Valve/5R55S Auto
1990 Mustang 306/AOD
2002 Explorer Sport Trac 4.0L V-6/5R55 Auto
2005 F-150 4x2 4.2L V-6/4R70W Auto

Post Reply
jlg2002
Guru
Posts: 1410
Joined: 03/08
Posted: 06/26/12 02:08 PM

Newer cars with keep alive circuits are going to drain the battery if the car just sits for a "period". The hard part of the definition is describing what is a "period".  To me, being an ex-automotive electrical technician & electrical engineer,  the "period" that makes the most sense is the amount of time where this current flow will draw down the energy in the battery to the level that negatively affects its state of charge.

Mark's method is certainly a good way to go after high current draws especially with easy to access tools. However, personally I like to use a Simpson DC ammeter connected in series the neg side of the system to get the real amp draw number. This can be tricky as some cars have circuits that keep alive for several minutes if not hours before relaxing to a down-powered state. At some point, less than 500 miliamps is going to be your normal keep alive draw (500 is arbitrary - based on what I've read and seen it can be any thing between 50 and 500). This draw will cause the battery to loose its state of charge.

Sorry for the long answer so lets cut to the chase:
Two ways to keep the battery from going dead if the draw is below 500 mA - solar/electrical top-off charger or unhook the battery  

Post Reply
cushman350
Enthusiast
Posts: 635
Joined: 07/06
Posted: 06/27/12 05:48 AM

Get and use one of these.

51AW%2B%2Biowrl  

Post Reply
ptomb3
New User
Posts: 3
Joined: 06/12
Posted: 07/05/12 08:30 AM

Hi
It has the factory anti-theft system, and the factroy MACH1 audio system (which takes up much of the trunk), but is used very little, and since I started having the problem, I always switch it and the AC "Off".
Thanks for the response ... we'll keep looking.  Sorry to be so long acknowledging, but my computer got infected with the s.m.a.r.t. repair trojan virus ... nasty little beast!
TomB  

Post Reply
ptomb3
New User
Posts: 3
Joined: 06/12
Posted: 07/05/12 08:33 AM

Hi
It has the factory anti-theft system, and the factroy MACH1 audio system (which takes up much of the trunk), but is used very little, and since I started having the problem, I always switch it and the AC "Off".
Thanks for the response ... we'll keep looking, using the info you all provided.  The info on a reasonable "keep alive current draw"  is very helpful. Sorry to be so long acknowledging, but my computer got infected with the s.m.a.r.t. repair trojan virus ... nasty little beast!
TomB  

Post Reply
waynep71222
Enthusiast
Posts: 455
Joined: 04/12
Posted: 07/06/12 02:35 AM

proper Parasitic Draw testing is done in several ways depending on the tools at hand...

the GREEN knob battery disconnect switch is one cheep tool that is needed... also a digital volt meter with a DC AMP setting..  some of 10 AMP DC some have 15 AMP DC and some have 20 AMP DC settings..  you generally don't need a meter that costs over 25 bucks..


lets go through the test set up..

engine off..  install the GREEN knob battery disconnect on either side of the battery..  connect the cable to the end...

while doing this.. you will be hooking your volt meter test leads to either side of the green knob battery disconnect switch..   set the meter to the AMP setting..  the amp set up also requires one of the volt meter wires to be plugged into a different hole in the meter face...

with the green knob tight...  start the engine ..   let it run a few minutes..    roll the drivers window down..   shut it off... take the ignition key and get out...   lock the door in a normal fashion..  either with your alarm fob or directly with the key.. which ever way you lock the car when you get out...

look at your watch...   after 6 minutes...  and the amp meter is properly attached to either side of the green battery disconnect ...   loosen the Green knob...     look at the meter reading.....

is it 0.030 to 0.040 milliamps...    3/100 to 4/100 of an amp..   that is what it should be...

you will probably want to disconnect the underhood light first...

in using a disconnect switch and the amp meter on both sides of the green switch.. you have NOT DISCONNECTED the battery...   but you have allowed all the various devices that stay on for short time after shut down to happen as designed..   now you should be looking at normal parasitic draw....


if you have more than the 0.030 to 0.040 amps..  get into the under hood fuse box and start pulling fuses one at a time while somebody watches the meter..

if you get no changes there..   you will need to open the door..  and get to the IN car fuse box.. the first fuse to pull is the dome light fuse.. so you don't have to hold the door button in..

hopefully the dome lights are NOT enough draw to overpower the amp meter..  most are fused..  some are not..

there are videos and articles around the internet on what i have described..


please...  NEVER disconnect a battery with the engine running..   you will usually destroy the alternator diodes and can blow out expensive electronics...  

also DON'T loosen the green knob with the engine running and the amp meter attached.. you will exceed the amp rating of almost any digital volt meter..

this is how the professional mechanics do the test properly...  

Post Reply
jlg2002
Guru
Posts: 1410
Joined: 03/08
Posted: 07/06/12 02:03 PM

Absolutely agree with Wayne on the methodology he's described (It hasn't changed since I was certified & professionally turning wrenches for living back in the late 70's/80's). I am a little hesitant to agree on the amount of drain quoted (40-50 mA) and 6 minute  time quoted that in my experiences leads to hours of investigation just to learn later it's "normal".  I've read about modern vehicles with keep alive circuits remaining energized for several hours on some cars and seen draw as much as 250 mA being considered normal.

-Wayne is there a specific document you quote or is it a rule of thumb or based on a written industry standard?  

Post Reply
bucala
New User
Posts: 36
Joined: 03/10
Posted: 11/18/12 06:53 PM

I found an issue with my SN95 Mustang.  Mine was doing much of the same.  CHECK YOUR KEY SWITCH.  I just had to replace the lock.  The "key present" switch inside of the lock assembly was registering that a key was inserted.

I replaced the key switch, and the problem is now gone.

Just my .02  

Post Reply
waynep71222
Enthusiast
Posts: 455
Joined: 04/12
Posted: 11/19/12 09:02 AM

Icon Quotejlg2002:
Absolutely agree with Wayne on the methodology he's described (It hasn't changed since I was certified & professionally turning wrenches for living back in the late 70's/80's). I am a little hesitant to agree on the amount of drain quoted (40-50 mA) and 6 minute  time quoted that in my experiences leads to hours of investigation just to learn later it's "normal".  I've read about modern vehicles with keep alive circuits remaining energized for several hours on some cars and seen draw as much as 250 mA being considered normal.

-Wayne is there a specific document you quote or is it a rule of thumb or based on a written industry standard?


Yes... i gathered info from my auto tech training about 30 years ago... and current articles ..

google    parasitic draw testing...   you will find info from which i gathered the test i have posted...

OBD2 cars.. 1996 and newer have some relays that stay on for up to 6 minutes after shut down...

but when you disconnect the battery... they turn off instantly.. and when you reapply the battery.. they may NOT power up unless you run the engine ... and start the shut down sequence again..


look over at motor.com in motor magazine...

look over at babcox.com   in underhood service...  import service also ..

look over at motorage magazine..

these are industry trade magazines that you won't see on a news stand..  

Post Reply
waynep71222
Enthusiast
Posts: 455
Joined: 04/12
Posted: 11/19/12 09:03 AM

Icon Quotebucala:
I found an issue with my SN95 Mustang.  Mine was doing much of the same.  CHECK YOUR KEY SWITCH.  I just had to replace the lock.  The "key present" switch inside of the lock assembly was registering that a key was inserted.

I replaced the key switch, and the problem is now gone.

Just my .02


thank you for that tip... i never would have even thought about that switch..  

Post Reply
waynep71222
Enthusiast
Posts: 455
Joined: 04/12
Posted: 11/19/12 09:18 AM

here are a few links.. to parasitic draw testing..


http://www.motor.com/article_pdf_download.asp?article_ID=1701


http://www.motor.com/article_pdf_download.asp?article_ID=1726


otc sells this modification of the green knob with a few holes drilled and tapped to hold your test lead probes...

41Z3goibdvl  

Post Reply
jlg2002
Guru
Posts: 1410
Joined: 03/08
Posted: 11/21/12 02:58 PM

thanks for the articles.  

Post Reply