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Cadillac Repair/low voltage alternator

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Expert: - 1/21/2010


Question
I have a 87 caddy delagance. My alternator has a low voltage output. I have replaced battery and the alternator is new. I purchase that and batt new. The reason why I did that is because the batt keep dying. I mounted the alternator the car ran for about 2 days then the batt died. I then check batt which was fine and also the alternator which was fine. But the voltage is only 12 and chnage. I checked the wiring to the batt and the ground mount but I still can't get the voltage up and the regulator is in the alternator

Answer
Hello,

The alternator is not working, whether you changed it or not. If working correctly, you should see about 14.2 volts. The 12 volt reading you have is only residual battery power which will cause the engine to stall when it gets to 9-10 volts.

You could have a bad alternator even if replaced, bad wiring to and from the alternator. You could have a blown guage fuse as well.

When the alternator is working with engine running and lights on, the alternator will make a screaming sound.

Rob

Cadillac Repair

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Rob Painter

Expertise

Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?

Experience

Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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