1998 Mercury Grand Marquis Q&A
1998 Mercury Grand Marquis Question: battery light is on
new alternator (2-3 mo); new battery (installed today); new serpentine belt; new belt tensioner all changed today...but the battery light is still on (the red warning light on the dashboard). does it take time for the battery warning light to go off? - Visitor
no. check the wire ends on the alt. there is a connector with one single wire that tend to be a bad connection and trigger the light. by the way, did you check the voltage while running?? Roy - mastertech6371
Roy is right! It could be a bad or unsecured battery ground cable between the battery and chassis or chassis and engine. Turn on the ignition switch to the on but not run position do you see an icon on the instrument panel representing a battery, if you do not see this battery icon the alternator is not seeing power to allow it to charge. Start the engine does the battery icon go out. A more complex but good diagnostic test is checking "voltage drop" on the battery ground and power cables. You can find a video on how to do a voltage drop test on youtube. Put a volt meter across the battery terminals with the engine off, at rest the battery voltage should be 12.6 volts if the battery is fully charged. Now get a friend to start the car while you watch the voltmeter, the voltage reading across the battery should read approximately 14.6 volts if the alternator is charging correctly. - patrick mannion
The battery light may illuminate on the instrument panel because the alternator wire harness connector is damaged. A new connector kit is available and should be installed to correct this concern.
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