Chrysler Repair: cooling system runs hot (LHS 97)/fans dont operate, coolant recovery, radiator hose

Question
Kevin,
I have 1996 LHS 3.5L with a problem of running hot. So far the system has a new water pump (leaking), new temp sensor (bad), new therrmostat and a new radiator cap. The car runs fine while you are moving at speed but sometimes when you slow or stop the temp will start to rise. While running the car at home the fans will come on with the AC running, but will not with the AC off, unless I unplug the wires from the temp sensor. Then the fan will run but I lose my temp gauge. Is there another sensor I need to check? How can I get the fan to runn constantly if I need to. Any other ideas?
Thanks,
Joe

Answer
Hi Joseph,
There is only one sensor. It may be inaccurate or it may not be immersed fully in the coolant due to there being air trapped in the system nearby.
Read the resistance across the terminals of the sensor when the gauge reads more than 1/2 scale. It should be in the range of 700 ohms, which should be low enough to alert the computer to start the fans. If it isn't then I would try to remove any air that might be trapped:
It would be good to start with only a partially filled system, so drain off two quarts from the radiator drain and collect for reuse.
Then notice that the thermostat housing has a bleed valve and a nipple from which you can drain fluid. Put a 4' length of clear plastic hose on the nipple and direct the hose over the front of the car to a clean container to catch the coolant. Then open the bleed valve. Then slowly fill the coolant recovery bottle until fluid starts to flow out of the clear hose. The gently squeeze on the top radiator hose until all the air is exhausted from the system. Close the bleed valve and fill the system the rest of the way until it reaches the top of the overflow on the bottle. Remove the hose from the bleeder valve nipple and close valve. Then see if the fans are more responsive.
The fact that the fans come on for AC use and when you remove the connector says that the wiring is alright. So either the sensor is inaccurate or it isn't in full contact with the coolant due to air nearby.
Roland