Fan will not come on in my 98 crown Vic police interceptor

Check for codes in the computer. Double check relays and fuses just in case you were sold a defective one. If memory serves me right, there is no temperature sending unit that controls the fan. I think there is a temperature sensor for each cylinder head and the computer uses the information to determine when the engine needs cooling, thus starting the fan. In the Police Interceptor, the fan is controlled by the computer, still other components are required for the operation. I am a former Sheriff's Deputy and still remember that this was a very common problem because the cars are running most of the time; our number one was cooling fan motor failure. Perhaps your question is answered by other members with more knowledge.

Thank you this did help. However I do have a follow up question. If the motor is bad would the fan still be able to come on when jump started by the battery?

I would say that if the motor is bad the fan should not come on. Does the fan run at normal speed when started directly from the battery, or does it run somewhat slow?

Yes it runs at normal speed.

I replaced the radiator back in November and I changed the thermostat when it first tanned hot a week ago. I do not have any leaks at all. When it runs hot all the antifreeze squirts out from the reservoir top.

Did u find out the problem