Problems with a check engine light and check battery light
javk
01-21-2006, 11:17 AM
Have a 92 crown vic (LX). For the last few days I have the check engine light flashing for a minute or two and them dissapear. I'm thinking that can be related to the alternator, because the low battery light has been flashing too. Any ideas?. I also planning to change my alternator (95 amps) for a new one (~130 amps) and don't have and idea is there will be involve any other things with the change over. Need help!
ModMech
01-21-2006, 02:41 PM
Yes, low system voltage *can* cause the CEL to illuminate.
Before you replace a possibally good (expensive) alternator, make sure that the battery is good, and that the alternator is indeed bad.
Charge the battery if needed (12.5-12.6 Vdc at rest). Have it load tested (many parts stores like AutoZone will do for free). If the battery is OK, THEN check the alternator with a volt meter. You should see a minimum of 13.6Vdc from the alternator case to the (+) post on the alternator, if not it is bad. If you do see good voltage at the alt, now check from the (-) battery terminal to the Alt (+) terminal, reading should be exactly the same as before. If not (lower by 0.3Vdc or more), then you have a wiring problem. The most common wiring problems are corroded terminals, loose terminals, and broken wire strands - all these cause high circuit resistance and poor charging.
Check and clean ALL the battery connections that you can find AFTER disconnecting the battery of course.
Before you replace a possibally good (expensive) alternator, make sure that the battery is good, and that the alternator is indeed bad.
Charge the battery if needed (12.5-12.6 Vdc at rest). Have it load tested (many parts stores like AutoZone will do for free). If the battery is OK, THEN check the alternator with a volt meter. You should see a minimum of 13.6Vdc from the alternator case to the (+) post on the alternator, if not it is bad. If you do see good voltage at the alt, now check from the (-) battery terminal to the Alt (+) terminal, reading should be exactly the same as before. If not (lower by 0.3Vdc or more), then you have a wiring problem. The most common wiring problems are corroded terminals, loose terminals, and broken wire strands - all these cause high circuit resistance and poor charging.
Check and clean ALL the battery connections that you can find AFTER disconnecting the battery of course.
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