My heating and air system completely shut down after my battery died. How do I get it to come back on?

Is the battery / charge light lit on the instrument cluster ? Did you have the charging system tested , they'll do that for free at auto parts store ! Do you have battery voltage at the bigger wire at the back of the alternator ? This wire supply's the current to charge the battery ! The smaller wire in the connector supply's voltage to turn the alternator on. Your running down your battery that's why it shuts down . It's not the key switch . If no battery voltage on the bigger wire ,check fusible link at the battery ! all so check gauges fuse in the instrument fuse block it is a 10amp fuse . Do you have the battery symbol light , light up when you turn the key on ?

At best, this would really be hard to find, since you can drive it hours before it happens. You could start by pulling all the fuses one at a time check them and put them back in. This gets rid of corrosion contact problems. You can also do the to all the plugs. Sounds like you have a heat up problem. Some thing in the electrical system is getting hot and loosing contact. Things that would kill the engine would be , the ignition switch, the map sensor, the mass air flow sensor, And the engine control module. Parts inside of these can heat up enough to loose contact. Your's is going to be a hard one to find. Until the part completely dies.

The throttle body needs to be cleaned, grime in this area prevents the throttle plate from closing completely and allowing air to enter, making the air/fuel mixture lean. Make sure to clean the front and back sides of the throttle body. Also, disconnect the battery during the cleaning process to allow the computer to reset and relearn to the cleaned throttle body.

it sounds like sensor or relay is bad. should replace it. if it fails completly the fan may not come on at all,which would then cause the car to over heat and could cause head to crack.

You might consider bleeding out the air you might have in your cooling system after you opened it,drain it to replace radiator.Let it cool down open rad cap start engine watch the burps of air come up when air locks are out coolant starts to swirl as it circulates might drop fluid level to have coolant on hand to top up after wards shut it of with rad cap off let it sit for as long as you possibly can any remaining air locks will burp out.Once coolant completely down put your rad cap back be sure fluid is full reservoir as well.Now see if you have heat.

Check to make sure the battery is good bring it to a advance auto parts store they check the batteries for free. If battery checks out ok be sure to clean the battery trerminals and battery posts then reinstall and proceed to start the car after the car is running use a voltmeter to check the output at the large red wire where it bolts to the back of the alternator the reading should eb a minimum of 13.5 vols if lower than that the alternator must be replaced. The car shuts down when the battery dies because the ignition system must have a minimum of 12 volts to operate.

your alternator is not charging,have it checked out

When it dies, it won't start back up? Does it crank over after it dies?

Here is the most common cause of surges and stalls and low idle rough idle, it is the idle speed control air-bypass valve and throttle valve (IAC for short), they get full of gunk over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Here is the most common cause of surges and stalls and low idle rough idle, it is the idle speed control air-bypass valve and throttle valve (IAC for short), they get full of gunk over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.