QuestionI have a 96 disco. My dash lights go dim, radio cuts off, headlights also dim, no read of rpms,lose power when im driving, etc. I come to find that my battery is dead. so i buy a new one and the same problem occurs within a month. i take the car to my friends shop and he hooks up a meter to the alt and when i turn on all lights, heater, radio, and wipers; the voltage drops around 12. he put 2 different alts and same thing happens where it reads a 12 something. now i again buy a new battery but 2 weeks later my car wont start unless i get a jump, then eventually wont start at all. the battery was completely full when i let it sit in my lot for a week and a half. i just checked the battery and the thing was dead. how can the battery be dead when the car was just sitting there for a week +. whats draining my battery if it isnt the alt? (sorry so long)
AnswerHi Jack,
Your alt is generating just 12.? volts? Just a trickle above what the battery holds is kind of low. 14 is high and 13 is sold! My alt is giving out 13.1 and that's seems to work for my battery.
But lets assume that the alt is kicking out enough volts to keep your battery at 12 volts (barely). If you have a ground fault between the alt and the battery, the alts charge never reaches its dependent battery.
Here are some ground locations:
Right inner fender, behind the battery. Battery and EMC on 1994 & 1995 models.
Below the battery, inside the right frame rail. Battery ground.
Right of the left cylinder head. ECU, A/C compressor clutch on 1994 & 1995 models.
Right frame rail, inside the wheel well. Starter.
Left footwell, behind trim panel. ECM, key switch, radio, OBDII data link.
Right footwell, behind trim panel. Starter solenoid relay, park-neutral position switch, alarm, data link connector.
Left side of luggage compartment, behind access panel for taillights, above light assembly. Fuel pump, fuel level sensor.
If you think your alt is working fine then start looking for ground faults and shorts.
Final note: I've replaced alts on my Disco and I am convinced that they are the weakest link in the electrical system. The moment you start losing batteries I'd seriously consider swapping out the alt for another. You can pick up a tested alt from a salvage yard (wrecker) for about $50. Make sure your serpentine belt is not slipping off. You may have 12.02 volts but if the belt is slipping or the alt has serious internal problems, the readings may not show - unless you're willing to read them for more than a few minutes.
Best of luck,
JohnMc
