Sometimes Overcharging

Dec 1, 2008
Hi, I have a hair-pulling problem that any help would be appreciated. I have a 2001 LC. The problem is intermittent -- sometimes I can drive all day and everything is ok. The dash instruments include a voltage gauge and a battery idiot light. At rpm's above about 600, the voltage gauge approaches 17+ volts and the battery idiot light comes on. I have never had a problem with the battery discharging or slow start-up cranking. Thinking the battery might have an internal intermittent short - I replaced it with a new one over the weekend. Prior to this I replaced the original alternator with a remanufactured one which did not fix the problem. My mechanic put in a second replacement and still the problem was the same. Also, when this overcharging occurs the ABS and VSC dash lights come on. However, the battery warning goes back to normal and so does the voltage gage if the car idles at around 600 - depress the accelerator pedal and the problem reoccurs. I know that the car should not be driven with such high charging voltages - but, the battery shows no sign of boiling or of outside hotness to the touch. Thanks in advance for your suggestions.


May 8, 2004
Start with grounding the alternator casing directly to the battery negative terminal via at least a 10ga cable. If that doesn't solve it, it may be a resistance issue in the wiring between the alternator/battery/ground where resistance causes the regulator to get thown off and cause the output to elevate in order to create the "target" voltage. If the alternator tests fine on the test bench, then an intermitant overcharging issue sniffs of a wiring/sense/grounding issue. Have fun!
Feb 7, 2009
try to reproduce the problem, messure the volt at the alternator at the positive terminar it shut be 13.7 , 14.7 volt, the messure alt tha battery it shut be the same if not teste the resistan on the calbe betwing the pattery terminal and the alternator you may have a corotion on the terminal
Top Bottom