Radiator cooling fans run when car is turned off killing battery
Mechanic has traced all the wires for electrical short. none found. had to replace master computer. no help. when car is turned off or turned on fans run all the time. if ignition switch is in on mode(so radio can play but engine not on, fans do not run).problem does not appear to be in fans or in temperture switch that controls fans switching on or off.
Re: radiator cooling fans run when car is turned off...
The master computer controls one or more relays which control the fans. Usually the fans will come on sequentially as the engine temperature rises, first one fan, then both...and this is accomplished by up to three relays.
Usually, this problem is the result of a faulty temperature sender, or computer, but you do not state if the sensor was tested or replaced.
If you are SURE the temperature sensor (it's not a switch) is good, and the computer is good, you probably have a faulty relay.
Check your manual for the location of these relays and tap on them vigorously with a screwdriver handle...you may get lucky and find the offender. Otherwise, get another relay and replace them one at a time till you find the bad one.
If none of this works, you will need a REAL automotive electrician to diagnose the problem. Incidentally, I would not pay for new master computer if it didn't fix the problem !
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RADIATOR COOLING FAN NOT RUNNING COULD BE BAD ENGINE.COOLANT TEMPERATURE SENSOR IS FAULTY IF COOLING FAN IS NOT TURNING ON AT SET TEMPERATURE OF 196 TO 203 DEGRESS.CHECK SEE COOLING FAN RUNNING WHEN ENGINE RUNNING HOT.IF YES FLUSH RADIATOR , FLUSH ENGINE BLOCK, HEATER CORE,REPLACE RADIATOR CAP.MAKE SURE YOU HAVE 50/50 ANTIFREEZE AND WATER IN THE COOLANT SYSTEM.CHECK WATER PUMP WEEP HOLE IF LEAKING REPLACE WATER PUMP. IF COOLANT FAN DONT TURN ON 196 TO 203 DEGREES, YOU HAVE FAULTY COOLING FAN,SHORT IN FAN WIRING OR ENGINE COOLANT TEMPERATURE SENSOR FAULTY.IGNITION TIMING WILL CAUSE ENGINE TO OVER HEAT.
REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP.CHECK MECHANICAL COOLING FAN.SHOULD HAVE RESISTANCE WHEN TURN WITH HAND.IF FREEWHEELS FAN CLUTCH NEED TO BE REPLACED.CHECK TO MAKE SURE AUXILIARY ELECTRIC COOLING FAN RUNNING HOT WIRE COOLING FAN IF FAN RUNS.YOU HAVE FAULTY THERMO SWITCH LOCATED AT THE BOTTOM OF RADIATOR ON THE LEFT HAND SIDE ON 4 CYLINDER ENGINE FOR V6 ENGINE THERMO SWITCH LOCATED ON THE LOWER RADIATOR HOSE ON THE RIGHT HAND SIDE OF THE ENGINE COMPARTMENT. CHECK FOR BLOWN COOLANT FAN FUSE OR FAULTY RELAY.IF THE AUXILIARY ELECTRIC FAN DONT RUN WHEN HOT WIRED THE ELECTRIC FAN FAULTY.
You are off to a good start by testing the fans. Get a repair manual from your nearest autoparts store. I find them invaluable. Most temperature sensors can be tested with an Ohm meter. Or short the two wires together to trigger fans. If it has only one wire then ground it to the frame/body (negative side of battery). If none of that works (with ignition on / car off) then relay is bad. Also turning on the A/C should make the fans come on. Car does not have to be running, key in on position. This would eliminate bad relays or not.
HOT WIRE THE COOLING FAN USING CAR BATTERY AND JUMPER WIRE.IF FAN DONT RUN WHEN HOT WIRE REPLACE FAN.THE ELECTRIC MOTOR BURN OUT.IF FAN RUN WHEN YOU HOT WIRE IT.THE PROBLEM IS THE FAN RELAY OR OPEN COOLANT TEMPERATURE SENSOR
Check the fluid level in the radiator - after it cools down !
It sounds like you should replace the temperature sensor that controls the fan. This is usually located in the radiator and has electrical wires connected to it. Trace the wires from the radiator fan ( not the air conditioner fan!) to the sensor.
If the radiator is aluminum you may need special anti-freeze to prevent damage.
The cooling fans always receive power form the battery. The relays, when applied, allow the ground to pass onto the fan motors to operate them. Either your relays are stuck in the "active" position, or your fan motor wires (white with the black trace) are getting an unwanted ground. Remove all 3 of the relays, and the magnet clutch relay, see what happens. If the fans quit, the relays are at fault. If the fans continue to run, you have a fan motor ground wire shorted to the ground.