Blown fuse, bad thermal relay, bad fan motor, or bad wiring.
Try the fan relay switch if your fuse is not blown.
(second author) Another author hot wired their fan to check if fan(s) was still good.
Sounds like your fans did not move before and after you changed the thermostat (so you should have not written the word "now")? If just later, and because you may have accidentally messed with conductors when you changed the thermostat, then wiggle or clean your connections and possibly do a continuity check.
Depending on the year of the car, possibly near the battery there are a few relays (and maybe one by the fuse box inside the car or by the glove compartment). Lightly tap on them as they may be stuck. Worked for me for a stuck radiator cooling fan, as one was stuck on but that was stuck on not off as in your case so may not work the same.
could be your thermostat or you have no antifreeze coolant or your water pump is going bad
Could be a collapsed lower radiator hose, perhaps a bad thermostat.
By the thermostat
Stuck thermostat, scale build up in the radiator and engine block, radiator cap not holding correct pressure. or it could be your headgaskets
In the motor.
Dirty or plugged radiator Water pump Defective radiator cap Thermostat Cooling fan not operating hoses collapsing
to keep the hose from collapsing
Usually at engine end of upper radiator hose in housing
near the thermostat housing
A Cadillac Deville can be purchased at a Cadillac dealer.
located n housing at end of upper radiator hose.
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If it is leaking coolant. And you changed the thermostat. I would then move to this section. Flush the radiator and the heater core. This can be done at a certified shop with a reliable mechanic.
Should be in a removable housing at the engine end of the upper radiator hose
water pump or thermostat housing crack
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Maybe check both electical fans between radiator and engine.
Follow the upper rad hose from the rad to the engine and there you will find the thermostat in a housing. When replacing it make sure the spring on the thermostat goes toward the engine.
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