Chrysler Repair: Engine overheats in heavy traffic only, radiator fan, atmoshphere

Question
Hi Roland,
The 'temp' of my '94 LeBaron has been running above the middle of the gauge. The other day I was in heavy traffic and had to pull off into a service station as the needle was close to the 'H' line. Upon shutting the car off, it overheated. I let it cool, put water?antifreeze back in and was in traffic for a short time and she ran hot again. As long as I was moving, the gauge seem to stay in the middle. Can you help me with what the problem is? Thank you so much.


Answer
Hi Helena,
I suspect that your radiator fan is not coming on in response to the rise in temperature beyond mid-scale. This could be either that the fan system is not working or that the temperature sensor is not asking it to come on.
The first thing is to see if the system is working:
When you start the car begin by opening the hood. Then ask for A/C and when the compressor comes on and you get cool air notice whether or not the radiatior fan comes on. If it does then the system is o.k., if not then something is wrong with it.
If it comes on, then drive the car WITHOUT the A/C and when  it starts to rise above the mid-scale and threatens to overheat pull over and again see if the fan is coming on. If it is, then the radiator or water pump is not adequately exchanging the heat from the engine with the outside atmoshphere and I would suspect it is the radiator needs to be flushed. If the fan is not coming on then I would suspect that the temperature sensor is not telling the fan to come on and needs to be replaced (a $10 part and simple unscrew/screw replacement).
If the fan never comes on, then you have to check the fan by jumping power from the battery to its plug which is near the fan or better yet first check the fan fuse (yellow, #52 in the power distribution box behind the battery) and if that isn't blown then you need to try tapping on the fan relay in that same box, or just replace that relay which is the one that is at the outboard end of the row of relays in the box. But even before doing that I would jump battery power directly to the fan motor using a wire from each post of the battery to each of the pin plugs at the plug connection near the fan motor which you simply separate to disconnect. If the fan works and the fuse is good then the relay is probably bad.
So, give that diagnosis a try and let me know what you learn. Write me back if you have more questions or an answer to share. Use the "thank and rate response" tab below as I am going to be hard to reach for the next couple of days. I will get an alert by email and get back to you if necessary thru the allexpert site.
Roland