Why does my fan run at high speeds for my 2005 ls lincoln

under the hood in the roadside fusebox

Sounds like your fan motor may be going bad. Do you hear the fan click on? Is the fan the same one that is used for the radiator?
If the fan is the same, which I assume it is since the car is overheating, then it probably isn't a problem with the coolant temperature sensor (otherwise the a/c switch would still cause it to come on.)
What I would suggest is doing some electrical testing:
1)You can do this with the car off. Unplug the fan electrical connector and jumper wires from the batter to the fan electrical connectors and see if it runs. If it does, the problem isn't with the fan, but the electrical signal getting sent to it.
If it doesn't run with the battery connected to it, replace the fan or fan motor.
2) If the fan runs, then check the fan relay. There are a number of ways to do this, but one way is to remove the relay and apply a small amount of voltage and listen for it to click. You can then use an ohm meter to test for continuity on the other side.

If both of these check out, we'll go from there.

the fan will turn on when the engine temp reaches a set temperature and will only turn off when the engine drops below a certain temp and on the highway running hard it may stay on longer

do u hav the rite thermostat or is it in correct--shud be closed at startup-if not takes long time to get at operating temp and bad gas milage too

the fan has a low and high speed or some have 2 fans. It comes on low speed when the temp starts to climb or when you turn the a/c, defrost, or mix mode (it turns on when the a/c compressor kicks on. If the temp of coolant gets to about 230 F, then the high speed kicks in.

What is your doing? Very nosiy sounds like high speed. Could be a defective ECT - engine coolant temp sensor.

The fan relay is bad.

hi

this is because the radiator may have chocks in it. so the rate of cooling might be reduced. so the cooling while normal running wil be ok but when you go in highways the engine generates more heat which in unable to cool by the engine.

try checking the cooling fan.this might have reduced the speed of running due to agening. so try replacing with high watt fan so that good cooling may takes place.

please rate me if the information which i provided was usefull for you. you can rate me by clicking on the thumb icon which is located on the bottom of the page.

You have a longer warranty on a Lincoln product than other brands. Its possible this can be a covered repair.

There is a diagnostic sequence on the digital dash models that can be done with the hood closed. If they want to check it in the drivethru bay it is possible.

Most likely it is a fan controller. See what they say and if they will warranty it. Some people get parts from Salvage yards or Ebay that work perfectly.

if it does not have electric fan the fan clutch is bad also radiator cap may be bad and the fluid in the raditor may be bad have it tested the antifreeze should be replaced every two years.

any coolant leak? check under the hood and the ground,