Car lights dimmed, battery light came on, wont start now?

Probably alternator. If the battery was bad, the engine would run okay but maybe not start the next day. Now it won't start, you could jump it but if it won't keep running when the jumper cables are removed, it's almost definitely the alternator.

Diagnosis at a parts place is free or nearly so - those guys love to feel like mechanics and the equipment practically runs itself so if they tell you your alternator's going toes-up, they're probably right. Alternators aren't really cheap but they aren't terribly expensive either, and if you're even a little handy with a tool set you can replace one yourself in under an hour.

I'm guessing you're a new/young mom. I know it's another expense, but I recommend you get AAA. If you get a breakdown, they'll tow your ride to the mechanic and they're usually pretty good about assuring which mechanics are reliable. That's one less thing to worry about with your munchkin along for the ride.

[edit] One responder mentioned checking belts because your power steering died - that's a good suggestion. But if your power steering is electrical, and a lot of cars' is anymore, then all the belts could be fine and your power steering would go out because the alternator has died.

But he's right - check the belts first. If you've lost one or the tensioner pulley has loosened, then you could lose your accessory drive and your alternator, power steering and other stuff would quit working. The good news is that's a pretty inexpensive fix - replace the belt, retighten the pulley where it belongs, and you're back on the road, no worries.

Don't just throw money at it.

If you also lost your power steering, check your drive belts. You may have just thrown a belt. Just open the hood and look on the end of the engine for pulleys without a belt around them.

If all of the belts are in place it sounds like it is the alternator from the way you describe the car lights dimming. But it should be tested first.

To test the alternator, you will need a multi-meter or volt meter that can test from the 0 - 20 volt DC range.

Set the tester to the 0 - 20 volt DC range. With the engine off, place the leads of the tester across the battery terminals. It should read about 12.5 volts.

Start the engine. You may need a jump. Place the leads across the battery terminals. The tester should read about 16 volts. If it still reads about 12.5 volts or less, your alternator or voltage regulator has failed.

The battery can be tested at most major automotive parts stores for free. Be prepared to take a little time as the testing time will vary. Some batteries will fail the test in a matter of minutes, however some may take over an hour to fail the test.

You can buy the new battery from the parts store. Many will install it for free and properly dispose of the old battery.

If you are mechanically inclined, you can remove the alternator yourself and bring it into any major automotive parts store for testing. Most places will test it for free. If it is bad you can buy a new one and install it yourself and save some money.

as it cranks OK? we need to look for another reason it won't start easily . battery wil go flat if we keep cranking eg bright lights then going dim. never crank an engine more than say 1015 seconds at a time leave approx 30 seconds to 2 minutes between cranking to allow battery to regain a bit of a charge ( it can recover a little bit) do check battery and connections though as if? it does not have at least 12.5 volts across it before even attempting to crank over we can forget trying to start. when we are sure battery IS fully charged ? make sure any choke system is in place before cranking over. if it wont start by third crank attempt we need to check things out eg: spark? fuel? timing? etc.

Now heres the answer, a car runs off the alternator, heres why they call it a alternator, it alternates between charging the battery and the needs of the electrical system. Your alternator is not keeping the battery charged and that cause all the other problems.

It's not charging - check the basic items first (belt tension and condition, associated wiring and so fourth). If nothing is visually wrong, charge the battery and take it to a shop to have the alternator checked - a lot of shops will check the charging system for free - it's a simple matter of checking the voltage at the battery with the engine running.

Have someone give you a jump start and let it run for a while, if it dies, then it is your alternator! The battery only supplies the juice to crank the car, the alternator does the rest of the work!

jump start car then disconnect battery if car stays running Battery is probably bad but the best thing to do if you have a multi meter is start the car and see how much voltage it has wile running if the alternator is working i should have around 14 volts

Buy and fit a new battery - you will soon know if it is your alternator.