2000 s-type v-8, occasionally when I start to drive, the car will max out on hot and the a/c goes off. I put in neutral, coast and turn off key. Turn on key, watch needle decend to normal rather quickly, restart and fine, sometimes must repeat 2 or 3 times. Sounds electrical to me, but not sure if it would be the PCM or fan module. And quick tips?

 

Could be a weak thermostat

 

It'll be bad for it, whatever it is.

 

+1 on bad or partially collapsed thermostat or air pocket in cooling system - I would investigate before driving...

 

If you get an OBD tool you could check the actual sensor values to confirm whether they are consistent, in case it's a bad sensor / bad wiring instead of the thermostat. An IR gun would also be handy.

 

@ JagV8, what is and OBD tool and an IR gun? Should I try removing the thermostat to see if it's that or electrical?

 

OBD tool is a code reader, IR is infra red fro checking temps.

 

Checking the sensor readings is easier than inspecting the thermostat. This should be your first step - if your temp sensor checks out then go inspect the thermostat - also, look at the connector to the temperature sensor.

 

I had something very similar happen, although it never overheated, but the aux fan would kick on and stay on for a good period of time.
It turned out to be the larger spring in the thermostat was put on upside down, so that the smaller diameter end was pointing down and the larger diameter end was pointing up. The spring would get caught on the copper end of the thermostat and jamb it closed. When the temp got hot enough, the pressure was enough to pop it open...rinse repeat.

I ended up replacing the thermostat anyways, but I could have just reversed the spring.

so for yours, just get a new thermostat and gasket and replace it.
Sometimes the simplest fix is the correct one

 

did a quick inspection for leaks, cleaned all electrical contacts, and so far so good after 2 days, (knock on wood)!