Radiator fan on 03 crown vic runs all the time. coolant temp sensor for the computer?

On some vehicles the coolant temp sensor is separate from the radiator fan switch - there are actually two sensors. We would need to know the manufacturer, year, make, and engine size to make better determination of the cause of your problem.

I would start with the temperature sensor.

Sounds like you have a double problem . First locate the radiator fan relay it should be in the fuse box change the relay. Also change the tempature sending unit (attached to radiator) . If your car is overheating . You need to check. For a leak, be sure you have enough. Fluid in radiator, check. Thermostat , change it anyway cheap enough, ( 16 lbs. pressure ) this should solve your problem

There could be a number of reasons why the fan is not coming on. First of all, it will not come on until the temp reaches a level necessary to have it on. In addition, if the a/c is on, it should be running at all times while the a/c is on. If your car has a/c, turn it on and check to see if radiator fan is running. If not check the following, coolant temp sensor, radiator fan relay fuse, radiator fan motor, coolant fan switch and temp sensor. Start with the easiest, the fuse and work from there. Most switches and sensors can be tested with a simple ohmeter.

If the sensor was the problem you would have a check engine light on, the fan is operated by the powertrain control module which controls a relay module. You must have the dealer run a scan of the system ans do an active test on the fan operation to determine what is wrong.

your coolant temp sender could be bad. locate the temp sender. this is a 1 wire sensor. the other sensor in the block has 2 wires and starts the cooling fan.

i have a 99 crown vic suvillan and i cant find the ambient air temp sensor where is it please help

The fan motor resistor is most likely bad. It guages the temperature of the coolant and controls voltage levels to the fan. It acts as a switch, similar to a coolant temp sensor does in the engine. Good luck!

-d-

it's funny to be reading about a similar situation i'm having. i also have a '97 crown vic, bought at a municipal auction.
of course, running the a/c should put more load on the engine and produce more heat. but not enough to be concerned about. if you car seems to be overheating, the thermostat could be to blame.
while diagnosing a different matter, i noticed the coolant temperature at one point reached 217 F. i'm going to replace the thermostat as it may only be opening partialy. my temp gage is normally just above the half way point between the high and low marks. it hasn't gone any further towards the high temp mark to be alarming.
where is the needle pointing on your gage? have you replaced the thermostat?

you ether have a coolant leak or one of these are the problem thermastat,fan clutch,water pump,radiator, try this start car when it reachs normal temp open hood and pinch the top radiator hose if it is hot water is flowing thermastat is good now open radiator with a towel slowly while it is runing see if the water is moving if it is you water pump and radiator are good, now at some point in this time you should have heard the fan get loud if not your fan clutch is not work it mounts to the front of your water pump and is normal to go out because they lose about 250rpm a year which does not give them much of a life, dont forget to check your heater hoses they could be leaking