Over heating The two fans up front are not coming on, and I will test them with a battery. Is there a way to know if it's the sending unit or the t-stat?

check and test motor under dash behind the glove box test resistor [fan speed ] and fan both connections are access able

Either the temp sensor is bad, or the relay is bad. or the fan motor is bad. Or you have a blown fuse.
Look for fuse first.... To test if fan motor is bad disconnect the connector to the fan and jumper it to the battery.if it spins it's good. the other two. use a component locator to find their location and replace. they are inexpensive. Temp sensor is in the cooling circuit (radiator...maybe next to thermostat) the relay will be in a fuse box under the hood.

1 in the intake man. 1 in the cyl. head

Has anyone tested the new temp unit to make sure it's functioning properly? Or is their possibly a mechanical thermostat in it that's hung and needs to be replaced?

Your vehicle should have a viscous fan clutch for controlling the engine temp from overheating. The auxillary fans in front are used when the a/c is on. I would start by spinning the engine fan or viscous fan by hand when the vehicle is off. The fan should show resistance when you spin it. If it doesn't and it just free spins then the viscous fan clutch is bad. Let me know what happens when you spin the engine fan and also exactly how high does the engine temp get. Does it reach the red mark?

Put it back in the factory configuration with a new sending unit,and make sure it is the exact part you need. See if that works. don-ohio

Hi!!

Apply 12v current straight to fan from battery to test fan motor, if it starts, then check the coolant temp. sensor, usually on or near thermostat housing. Also check for broken wires and loose connections.

Good Luck!! Don't forget to change this post!!

climate control units in most cars use the ac system to regulate temp in the cab. the ac system requires a fan to pull air over the condensor on the front of the car. its normal for a fan to come on. unless you have a bad engine temp sending unit thats causing the engine cooling fan to come on improperly. try turning off the heat and ac and see if it still comes on.

Fan does not necessarily get jammed when it fails.. Unplug the fan and hot wire it to the battery. If it comes on, it's good if not, change it. If it comes on when jumped, check the fan relay. Many jeeps have three fans. One that comes on with a/c, one that is operated by the temp control system and a mechanical one that comes on when the engine gets hot (has a heat sensitive lock up feature)
The automatic one operates as follows: temp sending unit sends signal to the computer which sends ground signal to the relay which then sends power to the fan. Likely that is the malfunctioning system you need to check. Some relays are in the power distribution center and sometimes the relay is tucked in front of the battery.

The water temp sensor is located near the thermostat housing. This sensor is what tells the ECM to turn the fan on/off. The water temp sending unit is located near the same area. You know you have the correct sensor is because the water temp sensor has a 2 prong plug. The water temp sending unit only has 1 prong.