Put a new battery in. alternator not charging-put in a new alternator still not charging. machine showed a drain on the battery what could this be?

If the lights drain the battery when the engine is running, then you have a bigger problem of the alternator not charging, not working. When the engine is running, the alternator supplies all the current to run the car's electrical systems, while also charging up the battery for the next start-up. If you know the alternator is good, then maybe a fuse or fusible link has blown, preventing the alternator from working. To check, put a voltmeter on the battery with engine running-it should show over 13.5 volts if the charging system is working. If the alternator is not putting out, the voltmeter will read same voltage on the battery as when the engine is not running. A fully charged battery should show "around" 12.6 volts. A discharged battery will show less than 12 volts. That should give you an idea of the range to look for on a voltmeter. I believe some parts stores will check the voltage for free. I know most stores will test the alternator and battery for free if brought into the store, but you need the voltage read while on the car and engine running. If the system is charging normally and the lights kill everything, you may have a short in the lighting system.

If you have a drain on your battery , it would not take 18 months for the battery to go dead . What do you mean The battery gauge in the dash shows only about 1/2 power, When ? When the vehicle is running ? Not charging ! The battery gauge as you call it has nothing to do with the Battery . That's showing how much the charging system is putting .The volt's indicator is controlled by the PCM - engine computer . With the engine running should show 14.1 volts .if your only seeing 7 the charging system isn't working. The alternator is controlled by the PCM as well ! Have it check by a GM dealer .

03 Mustang GT (Parasitic) Battery Drain Fix

Hello,
I am seeing a lot of mustangs are having battery draining issues and I wish to share some simple solutions found while working on a friends 03 GT 4.6ltr.

In a quiet area, key switched off, hood up, Listen carefully close to alternator. I heard a high pitched hissing/whistle sound at low volume, came from back of alternator. This sound was the voltage regulator/rectifier staying on when key is off due to faulty diodes inside the voltage regulator/rectifier circuit, can cause battery to go dead after car not ran in about 2-7 days.

After having the alternator tested free at a parts store, test showed alternator was good because the faulty diodes in the alternator did not show up on the test, the machine did not test for faulty drain back issues that were present.
Alternator on-car-fix:

There was battery voltage running at all times through the two-wire connector on back of alternator. Disconnect the battery first for safety and to reduce chance of short circuit. The yellow wire/with white stripe is hot while car is off so I traced this from the 2-wire connector on the alternator then closer towards driver side front fender. Next I cut the Yellow/White Stripe wire, spliced a good connection wire to it and ran it through a hole in the fire-wall to the fusebox(under dash), connected it to a 15a fuse that does not get used but has power when key is turned on but no power when key is off.

The purpose for re-routing the hot wire to the alternator, is to turn off the alternator charging circuit when the key is turned off so it may not run down the battery. I am seeing good results with this fix(or patch) so far. No More Parasitic Battery Drain!

Another fix can be to change the small pulley on the alternator to a larger pulley so the alternator does not spin too fast, putting too much energy through the diodes can cause a charging system to act a fool. So if you have charging issues and have an alternator changed, putting a larger pulley on can make sense turn into saved dollars(especially on high revving engines).

I hope this info helps to solve some draining battery and/or alternator issues.

for reading,

TyBorg1

check with a volt meter if u have 12 volt at the big lead on the back of the alternator engine off

if thats good start engine check to see if alternator is charging check the battery a good alterntor charges 13.5 - 14 volts, u may have a bunk alternator

altenators have to be running a 13.5 volt charge to be good

Why do you feel it isn't charging. Are you going off of a voltage ereadiing? I ask because if it is reading 12 v at the battery , Do not run it very long. The lower the voltage the higher the amps. An Alternator will ocweheat and self destruct if it is working at its high limit for 15 minutes or so. A heavy charge iis normal for 30 seconds or so to make up for the starting drain. But, should show a gradual rise within seconds. An alternator is for battery charge maintenance only and should never be used to charge a dead battery. A dead battery can an will over tax the alternator for too long. A defective battery will do the same thing and it is usually why you have to change the alternator in the first place. So, If your battery is dead or extremely lpw, it should be charged with a charger Do not put a new or rebuilt Aly. sgainst a possible bad battery. It costs nothing to have your batt load tested by a auto parts store. Good Luck=Ned-.

SOUNDS LIKE AN ALTERNATOR PROBLEM THE SYSTEM IS NOT RECHARGING ITS SELF AS IT SHOULD AND THEREFORE IT IS DRAINING THE LIFE OUT OF YOUR BATTERY AND WILL EVENTUALLY KILL THE NEW BATTERY TOO.

take it to an autosparky ......They will check to see if there is a drain on the battery.
cheapest and fastest option.

CHECK THE FUSE OF THE ALTERNATOR OR CHECK IF THE ALTERNATOR IS CHARGING

if the alternater light is not on the battery.probably has a bad cell