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Hey Guys, I have a 1972 mustang which is currently experiencing a battery draining issue. I just recently bought a brand new Bosch Battery and 3 days sitting without it being turned on drains the battery completely. The alternator has been tested and it seems to be fine and Just bought some new battery cables. I check the voltage regulator but it doesn't seem to be connected at all. My Mechanic told me that because i have an newer engine on the car the alternator has an internal voltage regulator so the external one isn't needed. Does anyone have an idea of what could be causing a drain to the battery?

*The car does have an aftermarket stereo, but this problem arose long after the stereo was install.

*The engine is a 1981-85.
 

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An easy method is to turn everything off, and disconnect the battery negative connection. Then place a test light or multimeter (set for amps) from the cable to the battery terminal. In effect, the battery is re-connected. If all was well, the test light or ammeter would show zero current flow, and therefore no drain. If you have a drain, the light or meter will show the current flow. Note that you may have to pull your dome light or courtesy lamp bulbs to have the door open without causing another drain during testing. ;)

Now, begin removing fuses one-at-a-time. Watch the test light or meter to see if the drain stopped. If it does, that is the circuit with the problem. Check that circuit in your shop manual wiring diagram to identify what is causing the drain. Test those items and wiring and repair the issue.
:tup:
David

PS: All classic car owners should have a copy of the Ford Shop Manual (FSM) for their car to reduce frustrations and costs. Although crappy copies, the wiring diagrams here and here may help for now if you don't have your FSM copy yet.
 

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Much better than my crappy copies! :tup: BTW, your car originally had a 1st generation alternator (1G). The engine may be '81-'85, but the 2G alternators in those years still had external regulators. It is even newer (Ford 3G) or an aftermarket model. Maybe a couple photos will help to ID it.

David
 

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GENERAL INFORMATION
The term Parasitic Load refers to electrical devices that
continue to use or draw current after the ignition switch is turned to
OFF position. This small amount of continuous battery draw is
expressed i
n milliamps (mA). On Ford Motor Co. and General Motors
veh
icles produced after 1980, a. typical Parasitic Load should be no
more
than 50 miUiamps (0.050 amps).
Vehicles produced since 1980 have memory devices that draw
current with ignition off for as long as 20 minutes before shutting
down the Parasitic Drain. When Parasitic Load exceeds normal
specifications, the vehicle may exhibit dead battery and no-start
c
ondition.
Follow test procedure for checking Parasitic Loads to
c
ompletion. A brief overview of a suggested test procedure is included
along wi
th some typical Parasitic Load speciftcatfons. Refer to the
G
ENERAL MOTORS PARASITIC LOAD TABLE chart.
TESTING FOR PARASITIC LOAD
INTRODUCTION
CAUTION: Always turn ignition off when connecting or disconnecting
battery cables, battery chargers or jumper cables. DO NOT
tur
n test switch to OFF position (which causes current to run
thr
ough ammeter or vehicle electrical system).
NOTE: Memory functions of various accessories must be reset after
the battery is reconnected.
The battery circuit must be opened to connect test switch
(shunt) and ammeter into the circuit. When a battery cable is removed,
ti
mer circuits within the vehicle computer are interrupted and
immediately begin to discharge. [f in doubt about the condition of the
ammeter fuse, test it with an ohmmeter prior to beginnrng test. An
open fuse will show the same reading (00,00) as no parasitic drain.
Beg
in test sequence with the meter installedand on the 1 O-amp scale.
Select lower scale to read parasitic draw.
 
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