Fan comes on hours after sitting and drains battery.what is causing this??

Yes it is the alternator that needs to be checked as it is almost certainly not charging correctly.
If the car has a high mileage the brushes in the alternator will be badly worn and the voltage regulator would also need to be replaced. Often people will just replace the entire alternator unit rather than disassemble the alternator and replace parts.

Did you recently change the coolant or have it changed? The system needs to be 'bled' or 'burped' of any air in the system. I did this for a friend once to fix an overheating issue.

There is likely a relay for the fans or the coolant temperature sensor that is bad. You'll need to get a Haynes repair manual (library) or look online for a service manual for your car...also, search the online dodge/plymouth/chrysler forums.

My guess is the relay that is bad IS causing a fault to ground that is draining the battery, too.

You could just remove the Negative battery terminal every night 'til you get the fans figured out.

Since it's overheating while idling it could be:
-water pump
-thermostat
-radiator plugged
-low coolant

Unfortunately, these engines have a history of blowing the head gaskets, too.


GL,
Td

Most likely you have something draining the battery. Quick way to tell, disconnect the ground (negative) cable to the battery, let it sit for a few hours, then reconnect it and try to start it. If it starts OK, you know the battery is holding a charge, but something is draining it.
To drain it in just a few hours requires a serious draw, like headlights or the cooling fan. It is possible that your cooling fan (behind the radiator) is staying on all the time. Often they are controlled by a thermostat, and will run for a few minutes after you shut off the engine, but it should shut off within about five minutes. If it is still running after ten or more minutes, you have a bad fan thermostat or a bad fan relay. If that is not the problem, you will have to get someone with an ammeter to measure the current draw, and start pulling fuses until you find the culprit.

There is a cooling fan relay that is temperature driven and it tells the fan when to kick on, that relay is bad.

In most newer vehicles there is a built-in battery drain caused by features that have a "memory" such as your radio.
Especially in cold weather, that drain is too much for a marginal battery to deal with.
If you are charging the battery by running the engine, that won't help. The battery needs to be fully charged with a battery charger. Load test the battery after charging. If it fails or comes up as marginal, replace it. otherwise, you will need to begin testing for an excessive power drain.

most fans don't come on until about 220 degrees so u might not letting motor get hot enough to turn fans on let it sit and idle for a good half hour but stick around and keep eye on it cause fans will only come on for a minute or two
also on some systems one fan will come on when u have air condtioning running but not all
if fans still dont work look to make sure relay not bad
also check to see if fans themselfs still work with rock stuck in them could of burnt them up
to check fans unplug eletrical connecter from fan useing two jummer wires hook fan directly to battery and see if it runs

water temperature sensor

Sounds like something is shorting out but first I would not trust that the battery is good . So try unhooking the battery after its been charged and then hooking it up the next morning to see if it will start your truck and if it works the battery is good and need to find the short but if it is drained and dont start truck its a bad battery.

There is some things to check....

(1) Is your alternator charging? take your vehicle to Advanced Autos, Napa or someone like that and have them test your alternator.
(2) Is there something in the vehicle causing excessive drain on the battery when the motor is not running... like is the interior light may be on or something to that affect.
(3) Are you doing enough driving to recharge your battery? short stops and starts is not good for a battery as you may rob more energy from the battery then you are putting back in.
Sounds like something is draining your battery, something must be left on in the vehicle, Advanced Autos or Napa should be able to tell if something is draining your battery when the vehicle is off.

Sounds like the radiator fan might be staying on and not switching off causing the battery to drain when you're parked. Could be a defective fan switch or more complicated the wires going to or from the fan module or the fan module itself.