What can cause radiator fans not to operate on a 1998 Cadillac Deville

If you look by the Radiator there will be an Electric fan motor. This Radiator fan may have 2 speeds. When the A/C is turned on, it will turn on at least low speed. Otherwise Water Temperature sensors make it work and spin to cool the Radiator.

You need to have this circuit checked. You need to find out if the Electric fan is any good and if both speeds work. The sensors for the fan may not be turning it on or may not be turning it on with High speed. Some Models have a Water Temperature sensor and some have a second sensor just for the Water gauge.
You need to investigate just the part that turns on the Electric Radiator fan.

There may be fuses for the Relays which operate this Radiator fan. The Relay that gets the signal from the sensor may not be working either.

While it sounds like a lot of parts, it makes sense when you know why the parts are there. A Temperature sensor turns on the Relay which has the strength to connect and maintain power to the Electric Radiator fan and operate the multiple speeds. If a fuse breaks, there is a bad part in the system. Just replacing a broken fuse will not fix the bad part.

You need to trace down the bad part and get it off your car. If you already have paid a shop and the car is not fixed, then they should investigate what I am writing to you. Morally, they should continue to test your car for the money you paid to keep it from overheating.

The parts you put on it already will not hurt and could have been part of the problem. Now you need to get the rest of the problem fixed.

Could be the cooling fan relay, the fuse, the sensor which triggers the cooling fan relay, or the wiring connections which join it all together. Is there power coming to the relay? Is there ground? Will the cooling fan operate if you trigger the relay? Try to break the circuit down in sections, and test a section at a time. If, for example, the fan operates when you trigger the relay, you will need to find out why the sensor is not triggering the relay. Maybe a bad wire? Or a bad sensor? Let us know what you find out. Good luck!

REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP.MAKE SURE COOLANT NOT LOW.IF ALL IS GOOD CHECK FOR LEAKING WATER PUMP WEEP HOLE IF LEAKING REPLACE WATER PUMP.MAKE SURE COOLING FANS RUNNING.IF ENGINE RUNNING HOT WHILE SITTING LONG TRAFFIC LINE AND COOLANT NOT RUNNING.CHECK COOLANT FAN RELAYS AND FUSE.IF ALL IS GOOD HOT WIRE MAKE SURE COOLING FAN MOTOR GOOD IF COOLING FAN DONT RUN WHEN HOT WIRED FAN MOTOR BAD.IF FAN MOTOR OKAY AND FUSE RELAYS GOOD YOU HAVE FAULTY COOLING FAN WIRING.YOU COULD HAVE BAD ENGINE COOLANT SENSOR OR FAULT IN ECM CODE SCAN TO CHECK THEM BOTH.CHECK ENGINE OIL.LOOK LIKE MILK SHAKE YOU HAVE LEAKING HEAD GASKET.IF OIL LOOKS OKAY.YOUR ENGINE BLOCK, RADIATOR AND HEATER CORE NEED FLUSHING.

several reasons
blown head gasket/cracked head ---have a compression test done
radiator cores blocked ---have a flow test done or replace the radiator
fan not operational --if viscous fan hub , replace it
if electric fans , check fan operation , check fan relay , 2 fuses , coolant sensor unit

the fans for the radiator or the blower fan that blows air in the dash? The blower motors are common to go bad.

check for power and ground at the fan. about 228 degrees is gm's temp for starting the fans. if no fan at that temp, check primary and secondary relays for power ground and signal from the pcm. signal should come from ect( coolant temp sensor for the computer, not the gauge)

You can check if the fans are working by turning on you Air conditioning. They should run constantly with the A/C on.
Also bear in mind that the fans do not normally come on until the coolant temperature hits around 225-228 degrees.

If your fans are not coming on then your engine is not receiving the signal that it is overheating. This can be caused by bad fans (unlikely they are both out) a bad relay, or coolant temperature sensor. I would start by checking or replacing the temperature sensor as it can become corroded which is what the PCM uses to turn the fans on. Many vehicles use two sensors, one for the gauge and the other for the ECU, make sure you check/replace the right one. It should be a cheaper part and if you are unsure then match the new one with its location; it should be on the intake manifold or near it, generally with one or two wires. I think you will find your problem as they are common failed parts.

Good luck!

Bad fan relay sensor, or fuses are bad.

the first thing to check is to have the engine running. as soon as it reaches operating temp the upper radiator hose should get hot. if it doesn't then it's the thermostat. if it does then i believe your water pump is probably not circulating like it should and it should be replaced. however before replacing the wter pump make sure that the wire to sending unit is tight and not giving you a false reading. if your model has electric fans make sure the fans are running when the engine is hot. if they are not running check the relay in the fuse box for the fans with the engine running switch out the fan relay with the a/c clutch relay. ifthe fans kick on replay the relay with a new one. if they don't click on the it's either a bad wire or the temp sensor probe is bad. hope this answers your question. please rate this solution...thanks.