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check the charge rate by putting volt meter across battery with engine running if between 13 - 14 volts alternator ok ,the ecu is a completely different part to the charging system , then check if battery is holding charge at a garage
have the battery LOAD tested,, you could have one cell bad in it , and it would make the alternator work double time to try and keep everything running and charge the battery , something has to give at that point, the LOAD test will show you if the battery is up to par amperage wise
the battery wont stay charged? if youre putting in a fully charged battery and your car runs, but then the battery slowly dies, the problem will be your alternator. the alternator is what maintains a car batteries charge. try replacing the alternator. hope this helps.
Sounds like a bad alternator. GM vehicles are notorious for failing starters, alternators and fuel pumps. If your battery light is flashing, your alternator is not putting out enough keep the battery charges and keep all of those electronics running. take a volt meter. You should get anywhere from 13.8 to 14.8 volts with your engine running and about 12 volts with everything off. Take the vehicle to your local auto parts store for a free charging system test. Advance auto parts can load test the battery and charging system.
Take it to a shop or auto parts store and have the alternator output checked, it may not be producing enough amps at idle to keep the electrical system properly charged. Please rate this answer, thanks.
" service charging system ", means you have an issue with your battery, your alternator, or your voltage regulator. Something is causing your battery not to charge properly. You should have it checked as soon as possible. This could keep your vehicle from starting next time.
The battery light means that your charging system isn't working, so you most likely have a bad alternator, or connection to the battery.
You can test your alternator with a volt meter.
First,get your battery 100% charged up. It should read about 12.6 volts.
Next, start your car, and check the voltage across the battery. It should be at least 14 volts. If not, you are not charging your battery.
Most auto parts stores will check out your battery or alternator for free, if you stop by and don't own or can borrow a volt meter.
If you have a fuse it will be in the power distribution center near the battery main fuses and relays are inside. Check the charging system with a volt meter right at the battery. Battery standing charge should be no lower than 12v if charging you should read between 13 and 14 volts running, about 13 with all electricals turned on. If not, the alternator isn't working OR the regulator has failed. (some regulators are part of the main computer but you need to check which system you have. AND do check for fuses. If charging system is working you may have a system draw that is pulling the system down overnight. Check that with an ammeter between either cable (removed from battery) and battery connection...pull fuses one by one till draw disappears then check components in that system. Don't be concerned with "low Draw" items such as radio that always pulls something to keep memory and clock working.
There are three main possibilities:
One is that your battery might not be making a good connection
somewhere, like a bad ground or corrosion at one the cable ends,
positive or negative. A bad connection will prevent the battery from
ever charging fully.
Also make sure no connections are loose.
Another possibility is that you may have a light or other accessory stuck "on" after you leave the car, like a trunk light, etc.
The third possibility is that there is a short somewhere in the
electrical system, in the form of a bare wire or malfunction of some
accessory which is draining the battery. Sometimes this can be very difficult or time consuming for us non-mechanics to figure out.
If you still have trouble after the battery and connections check out
okay, it's probably a good idea to have a mechanic isolate the problem.
On a side note, Caddies have a lot of power accessories so it's good to take them for a good highway drive once in a while to let the alternator fully maintain the battery. Use a battery charger to charge if the battery is really low. The alternator is really used for maintaining a charge, not charging. Using the alternator repeatedly for heavy charging will eventually cause your alternator (expensive) to overheat and fail prematurely. You may want to check the output of the alternator with a voltage meter. While running, the voltage at the battery should be about 13 -14.7 volts. While the car is off, the battery should be about 12.6 volts but no lower than 12. This may vary a little with the outdoor temperature. Make sure the water level in the battery is correct -- always use protective eye wear and use extreme caution any time you work around a battery. A good local mechanic won't charge much to do a basic check up of your charging system and this might be well worth it. He can also verify in fact if the battery is being discharged and how much. If there is a short somewhere, he is probably your best choice for diagnosing and fixing that.