The low water light stays on. the car has plenty of water. Its overheating, I know the fan is not coming on. Is the fan motor out or is there a sensor that may cause the problen?

that doesnt mean that its not overheating --have vehicle scanned can be a failed fan-sensor-water pump etc theirs multi reasons

How do you know it's overheating ? Are you going by the gauge ? Did you check the actual temp. of the engine with scan tool data . or A inferred heat gun at the upper radiator hose near the thermostat housing . Do the cooling fans come on ?Is the cooling system full ? Is there air in the system ?
A coolant temperature switch activates the fan motors. This switch regulates voltage to the cooling fan relay. This switch operates the fan whenever the engine coolant temperature exceeds 110°C (230°F). For location and diagnosis, refer to Electrical Diagnosis. A transducer can also activate the circuit, depending on the A/C compressor head pressure going to the condenser.
The engine cooling fan relays provide the high current required for the cooling fan motors using a low current signal coming from the Powertrain Control Module (PCM). This signal is a function of various inputs

There is an electric fan that should come on with the AC and run whenever the AC is on,if it doesn't come on it will heat up very quickly. Sounds like a problem with that radiator mounted fan.
The fan is supposed to come on when the engine gets hot enough also.
If so, the AC should be ok at hiway speeds.But you need the fan to work.

It could be the low oil pressure warning light. That light looks like an oil can with one drip of oil on the tip.
If that is the light it is telling you the oil pressure in the engine is low.
You might want to check with a dealer to make sure if you don't have an owners manual.

I would check the thermostat, do you know if the radiator fans work?

I would first check the cooling fans. To do this unplug the fans and use two jumper wires to hook them direct to the battery and test. If the fans are working I would have the radiator cleaned or purchase a new one. To clean the radiator take it to a professional and tell them you would like it rodded out. You can purchase a new one for about twice the price. I wouldn't worry about the low coolent sensor. By it being on it will not send a message that your vehicle is overheating. If you have changed everything that you say you have and the fans work and radiator is cleaned you may have a blown head gasket. If you have a blown head gasket you would see steam comming out of the tail pipes or water in the oil on dip-stick. Good luck.

sounds like a problem with the thermostat stuck closed and foorcing antifreese out the overflow leaving you with over heating car replace should fix problem around 20 bucks

Sounds to me like you are having a cooling system problem, if water is boiling in the tank or radiator then the engine is overheating. If you have not flushed the cooling system, it would be a good idea to do so. Also you need to test the cooling system at idle and see if the engine will maintain normal temperature, without overheating. Overheating can be caused by plugged or restricted radiator, hoses, or the thermostat, also check the operation of the electric cooling fan. Once you solve the overheating you light should stay off. If you do not solve the overheating soon, the engine will suffer major damage, so check it out very soon. Hope this helps, let me know.

What is your fan doing? Take it out for a spin and warm everything up. Park it in the drive and look at the fan right behind your radiator. If your fan is not spinning or cycling that's your problem. If your fan is spinning then my question to you is:, "Is your van overheating? And how do you know?" The gauge can be wrongor something else. Sorry if this didn't help.

thats a bit drastic maybe an air pocket in the system causing the light to come on and off