Jim Grant's Tech Tips
‘97 Ford Contour, More Charging System Problems
Q: Right after I start my ‘97 Ford Contour, often the battery light lights up for about 1 mile of driving. Using your recommendation, I had the alternator replaced ($460 parts and labor). This made no difference in that the light still lights up the same way. I never had difficulties with the car starting. Might the problem be with the circuit, which could, erroneously measure the voltage level and thereby turn on the light?
- Earl R.
A: Your problem is starting to sound more fun by the minute. When you turn the ignition switch on, electrical power flows through a fuse to the charge light and then goes directly to the voltage regulator, which just happens to be built into the alternator. Before the voltage regulator allows the alternator to start charging it needs to see a signal (electrical tickle) from the wire for the battery charge light. It's that electrical tickle from the charge light to the regulator that is the heads up to start charging when the engine is running. Without the tickle from the light the charging system would not work. Once the alternator is charging, a canceling voltage is applied to the battery light circuit, which turns the battery/charging light off. Therefore, if there's an erroneous measurement of the voltage level it would have to come from the voltage regulator inside the replacement alternator. The questions that have to be answered now? Is the charging system working when the battery/charge light is on and the engine is running? If charging, is there a cancellation signal/voltage present from the “I” terminal of the voltage regulator for the battery/charge light? If not, the replacement alternator has a problem. If there is and the battery/charge light is on, then you may have some wiring issues to deal with.