Chrysler Repair: 95 spirit overheating. fan does not come on when it should, coolant temp, dodge spirit

Question
Welcome back, Roland! I have a 95 dodge spirit with the 2.5 and it began overheating last week.

I topped off the coolant first and I went on my way. It lasted about an hour and then it overheated again. I noticed that over time, the fan wasnt coming on, so i got it home by running the AC on low to override the sensor for the fan. That worked for another half hour or so, but then the upper hose got rock hard. I replaced the thermostat(drilled it too), coolant sensor, the radiator cap, and the fan relay. No difference. I burped the system from the bleed screw. There was constant air, so i checked for bubbles in the overflow and there were. I pressure tested the system, and it had a slow leak (1psi over 10 min). I used a Universal Block Test kit (the blue fluid) to see if it was exhaust gas in the overflow; it was. I replaced the head gasket, head bolts, timing belt, and had the head pressure tested and resurfaced. The hg was definitely bad.

After all of that, I am back to square one. It does the same thing it did the first time, minus the head gasket symptoms. The hoses now have the correct pressure, and I am not losing any more coolant.  At first, the fan comes on at about 190, and everything is fine, but eventually, it stops coming on. The only way to drive it is have the A/C on.

So many people have this problem on the forums, but nobody has posted a resolution yet.

Any ideas before I wire up a toggle switch?

Thanks for your time.

Answer
Hi Eric,
It would appear that there is an issue with the coolant temp sensor not putting out a resistance reading that causes the fan to be activated. It should be in the range of 700-1000 ohms at notmal operating temp (200F) so check that. Then see what it reads when it does activate the fans, and see what it is when the temp gauge reads higher and yet the fans isn't activated. If the resistance is dropped further when the temp is way up then the problem is probably electical in that the pcm is not noticing the low resistance. The tan/black wire is connected to pin 2 of the pcm and the black/light blue is connected to pin 4, so check those for continuity and shake the harness. If the resistance isn't low enough to call for the fan, then you may have air trapped in the thermostat box. I am not sure that it is a good idea to drill a hole in the thermostat as it is not designed for that. So you might close that hole.
Setting that aside, I wonder if the flow across the radiator may be impaired. Are the temps on either side pretty similar, or is one side cold?
Check those out and let me know what you learn.
Roland