My daughter has a 93 eclipse that is draining the battery while it is sitting turned off. All lights are off and the alt light is off. The alt is charging at about 13v but drops lower at low idle until the car just quits. The battery is new. Any help??? snipped-for-privacy@charter.net
Does the alternator make an unusual purring or whining sound? A shorted diode would both reduce alternator output and drain the battery.
Testing: Disconnect negative battery cable. Connect 12v test light between negative post and removed cable clamp. If there are no shorts the test light will not light or be dim (load from ECU, clock, radio). To check for most shorts, start by removing fuses until light goes out. (Remove dome light fuse first so you won't have keep closing the door to see if the test light will go out).
To check the alternator, disconnect the large battery lead on the back of the alternator. If that is the problem, the test light will go out (or go dim).
Let us know if this helps or if we need to do more checking.
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