Battery draining

LucksMyName

New Member
Aug 17, 2019
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arizona
Recently got myself a 00 mustang gt from a family member without the car remote and keys as he lost it, so the alarm been on(Anti theft light blinks). I replaced the keys and can drive it no problem but the battery dies within a day without use.(bought new battery same issue). Im wondering if its the alarm system could be whats causing the problem?
 
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Sluggie24

Active Member
Apr 8, 2017
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There is an electrical draw in the system. The easiest way to find it will be to unhook the negative battery cable and hook up a multimeter between the terminal and the battery post. Set the meter to read amps. A normal memory draw will be below .5A when the car is off, key out and all doors closed. (Usually have to wait 1-2 minutes to ensure all modules have had time to power down.

First see how large the draw is. Likely a few amps. Start under the hood unplugging fuses one at a time and see if any single fuse being removed causes the reading to drop to below .5A. If none do try the inside fuses. The circuit that fuse powers is the problem. You will have to see what is powered by that circuit and disconnect one item at a time from that circuit to figure out where the problem is.

If you have to work inside the car to do this make sure you close the door latches with the doors open so the car doesn't see them as open as this would cause a draw and change your readings. The door latches can be closed using a screwdriver or similar tool.
 
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wmburns

SN Certified Technician
Aug 14, 2009
5,871
512
204
Houston Texas
Does the theft light blink slow (about once every three seconds) or fast (once per second)?

If the theft light blinks slow, this means that the system is working as expected and is standing by. Not your problem. Look elsewhere.
 
Jun 30, 2019
38
9
18
45
South Florida
Does the theft light blink slow (about once every three seconds) or fast (once per second)?

If the theft light blinks slow, this means that the system is working as expected and is standing by. Not your problem. Look elsewhere.
What happens if it’s fast? Mine sometimes is fast or steady on. I have an 03 GT, my lights pulse sometimes too, not every time. Shortly after I got the car last April I had to replace the alternator. Any suggestions? (Alternator is for 01 Bullitt cause that’s the Intake manifold I have on the car.)
 

wmburns

SN Certified Technician
Aug 14, 2009
5,871
512
204
Houston Texas
If a slow blink theft light means it's ok, what do you "think" a fast blink or on solid means?

Check out the crank with no start check list.

1996+ Crank with no start check list

Howto perform charging system voltage drop test

If you are really trying to learn how to trouble shoot your PCM, here's some information on something that will take your trouble shooting to the next level.

ForScan ODB2 scanner w ELM327 USB
 
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Jun 30, 2019
38
9
18
45
South Florida
If a slow blink theft light means it's ok, what do you "think" a fast blink or on solid means?

Check out the crank with no start check list.

1996+ Crank with no start check list

Howto perform charging system voltage drop test

If you are really trying to learn how to trouble shoot your PCM, here's some information on something that will take your trouble shooting to the next level.

ForScan ODB2 scanner w ELM327 USB
Thank you!