Thanks, but I have looked at a wiring diagram and I think I have it figured out. Electrically everything seems to work. It is the sensor that is not giving continuity to allow the fan to go on. I think the problem is in the radiator, unless someone has any other ideas.

 

What is the best way to flush without installing a kit, or should I install a kit?

 

Install the kit. It takes 2 minutes.

Queue reason for not using kit...

 

On a '90 if you suspect the radiator, I would replace it.
Anything else may be wasting good $ you could put towards a new radiator.

 

That radiator probably needs to be replaced but doing a flush will let you know, if the fluid is really grimey. I just took mine to some mechanic to do the flush because I live in an apartment complex, it was like $90 but whatever. The other thing I would look at is the water pump. Check your heater if it is working ok and blowing hot air then water pump is probably ok. On jeeps they don't always leak when they go bad...If you take an IR gun and point it where that sensor is for the electric fan, check what the temp is. Like I said that is not going to kick on until over 200*. On a 70* day you should not be getting that hot, it is very odd that the fan is not kicking on when you have the A/C on. Are you overheating any other time? Like on highway or while idling in traffic or stopped at a light? It is important that you burp this system if you flush it yourself but pulling off the temperature sensor is not necessary, a lot of people do it but you should burp the way the owner's manual says. It says that you let the car run to operating temp with the heater switch moved to heat, no fan running and add coolant as necessary. Any other air is supposed to move to the pressure bottle while driving around.

 

watchin this thread with similar issues plus or minus a few more