My cooling fans turn on as soon as i start my van.. fan wont blow heat in the cab either

Check rear AC in van and turn it off. Most vans have dual AC. Even if the front AC is off, the rear is still usually on and some vehicles have the cooling fan and condenser fan run together to help with cooling. Check relay and fuse also.

start with using a meter to test for power start from fan back to switches need to check harness and connectors

Your airconditioning system may be out of cooling gas, and if it has sufficient gas, the compressor might not pick when you put on the AC, and if the compressor did not pick ie start, you cant experience cooling effect, the fan will only be blowing.

Befor you replace the fan you need to check the thurmastat. Turn on heater and see if cools down the motor. Could also be your heater core going out. this supplys the water through your system to cool. as well as heat. good luck
If you do have to replace fan it should be under $100

The oil you described is called blow back, which means the oil leaking is blowing back on the bottom side of van,, Those vans are known for computor problems, Which means they need re flashed once they start like dash lites wont come on or cooling fan wont come on and van over heats,or wipers ,radio wont come on than all of a sudden they come on,,I just got rid of a nice looking 98 had same problems.Also the main bearing on yours is leaking oil, I wont buy that van.You do what you want but Dodge,cryseler,are cheap made vehecles, I just answered a 2000 van that had the reflash problem here on fixya.So look around.

Generally if the a/c works fine at highway speeds but kicks out or slowly begins to blow warmer and warmer air as the vehicle is driven at slow speeds or is stopped the a/c condensor cooling fan is usually at fault. At highway speeds there is enough air being forced through the radiator, condenser, and oil coolers to keep everything working and cool but when the vehicle is moving slowly or is parked the electric and mechanical cooling fans have to be working to pull enough air through to keep things working. If the cooling fan isn't working or can't pull enough air through the a/c condensor the system will kick out once the internal pressure reaches a certain point. Once the vehicle is moving again the system can get rid of the heat that it has gathered from the passenger cabin, the pressure drops back to normal and the system cools again. I would start by looking for a blown cooling fan fuse in the fuse panel under the hood. Usually they are 25 amps or larger and run only the cooling fan.

well it might overheat because air got into system, replace the thermostant and then fill system, run van keepin an eye on the temp, it will start to run hot because coolant has not filled the motor just the radiator, when it starts running hot shut it down, wait 3 minutes and start, now this is done with cap off,after restart coolant should get sucked in get filling radiator as needed,may get messy but got to bleed cooling system. hope thius helps.

you may want to check on the radiator fan. The AC has its own fan and once AC is on, the fan would help bring down the temperature. It is either the fan is not blowing or has become weak. You can check on the fan by pulling out the temp sensor on the lower radiator hose. The fan should blow at full speed when doing this.

Check on the water reserve the water inside it goes down, if not there may be a leak somewhere. Water vapor may be escaping and lessening the effectiveness of the cooling system. This may be a reason why the engine cools down after the AC fan is on.

100 % it will be the main blower fan for the heater/aircon has to seperate bits so the heater bit has gone

If the fuse is blowing there is too much resistance in the cooling fan moter. Replace JUST the cooling fan motor and the fuse. The A/C always turns the cooling fan ON when turned on. That is why the A/C messes up when the fan motor is bad. Replace the fan motor and the A/C problem will be fixed too. :)