2002 Cadillac Deville DASH READING LIGHTS STILL ON AFTER RE

Tiny
TRINITY7772008
  • MEMBER
  • 2002 CADILLAC DEVILLE
  • V8
  • FWD
  • AUTOMATIC
  • 80,000 MILES
GENTLEMAN: MY DASH BOARD COMPUTER INDICATED, BATTERY NOT CHARGING, THE SMALL RED BATTERY INDICATOR ON THE LEFT SIDE IS LIGHTED UP. TAKEN THE CAR TO THE MECHANIC HE CHANGED THE ALTERNATOR AND REPLACED THE BATTERY IN THE BACK SEAT. NOW HE SAID THE ALTERNATOR IS SURGING HIGH AND CAUSING THE BATTERY TO BURN OUT, ALSO HE CAN'T SEEM TO GET THE RED BATTERY LIGHT TO RESET, ALSO HE SAIDTHERE SEEM TO BE SOME ELECTRICAL PROBLEM WHICH HE CANT FIND WITHOUT TAKEN THE ENGINE OUT AND CHECKING EVERY ENGINE WIRE. ALSO CHECK ENGING COOLANT KEEPS COMING ON THE COMPUTER SCREEN, BUT THE RESERVOIR IS FULL AND NOTHING IS WRONG. HELP PLEASE.
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Saturday, March 20th, 2010 AT 4:13 PM

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Tiny
CARADIODOC
  • EXPERT
The voltage regulator is built into the new alternator so normally surging voltage would be blamed on it, but if you have a digital instrument cluster, they use a wire to sense system voltage there because it is more critical there to prevent the display from flickering. There is likely to be a problem in the instrument cluster causing the surging voltage. And voltage that is too high CAN damage a battery.

Look at the small electrical connector on the side of the alternator. If there is only one wire in it, (red or brown; I can't remember), the voltage regulator senses system voltage internally. If system voltage is wrong, the new alternator is defective.

If there are two wires in the connector, as a test, your mechanic could disconnect the second one, (white as I recall, but I'm not sure). That will make the new alternator sense system voltage internally instead of from the instrument cluster. If that brings system voltage down to normal, that wire or the instrument cluster has a problem.

Normal system voltage when the engine is running is between 13.75 and 14.75 volts. Lower than 13.75 volts, the battery will not charge fully. Higher than 14.75 volts, and water will start to boil out of the battery. A little bit higher voltage, say up to around 15.25, will not cause a problem as long as it holds steady.

GM alternators since 1987 can cause voltage spikes too due to their design. Those spikes can wreak havoc on the dozens of computers on your car, and can confuse the voltage regulator. It is quite common to replace the alternators on GM vehicles four to six times in the life of the car. Most mechanics have found that to prevent repeat failures, it is best to replace the battery every time they replace the alternator.

Caradiodoc
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Saturday, March 20th, 2010 AT 5:01 PM

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