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Re: what is a cooling fan s/p (relay)?
They are all in the fuse box under the hood the relays dont work in a way where one controls one fan and one controls another fan they run the fans in series for low speed and paralel for high speed. They are numbered 37,39,40 you would have to replace them all to see if that takes care of your problem
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Check fuse for cooling fan, check temperature sensor functioning for cooling fan, check relay for the fan (if you have one), check cooling fan motor circuit with resistance check (should read low Ohms, less than 2 Ohms beacause the fan is a powerful motor with 10-20 Amps). If everything is measured O.K. you should check the wiring. Disconnect the connector at the cooling fan motor, connect a test light to the harness from the car (not to the motor side) and run the engine. Watch the temperature gauge and before you the boiling (overheating) the bulb should lit up. If not you should go back with this test step by step to the relay. The relay can be tested if you can find a same one on your relay board and swap temporary (e.g. swap the AC clutch relay with the cooling fan relay)
if engine at long stand still,the engine temperature will rise about 190 degrees the cooling fan suppose to automaticaly turn on when coolant temperature sensor get hot it cause its resistance decrease causing pcm to send power to coolant fan relays and cooling fans, when you turn on AC the cooling fans suppose to turn on to cool down AC CONDENSOR, IF NOT AC WONT WORK COOLING FAN COOLS DOWN REFRIGERANT SO IT CAN RECYCLE THROUGH THE SYSTEM AGAIN.your cooling is suppose to turn on when engine at a sit still if vechicle not moving as coolant temperature rises at a set point the cooling fans will turn on cool down engine.cooling fans dont turn on when you first cold stsrt vechicle unless you have AC SWITCH ON.if cooling fans dont turn on when vechicle at a long stand still or moving along slow traffic.if coolant temperature sensor been replaced and fuses and relays okay have dealership check see if pcm driver circuit working faulty pcm will cause cooling fans not to turn on.
Check that you have both sufficient voltage and AC system is properly charged. Also that your idle is set correctly. The idle should be higher when you turn on the AC. Does the idle increase / decrease when you turn on / off the AC? Low voltage from the alternator could cause the AC not to work properly but .... I would suspect you would notice that you have very dim headlights at idle if the alternator was not working correctly. The amount of charge in the AC system will definitely cause this type of problem.
HIGH PRESSURE CUTOFF SWITCH LOCATED ON AC COMPRESSOR DISCHARGE LINE LEADING TO THE CONDENSOR.THE HIGH PRESSURE CUTOFF SWITCH WILL CUT OFF THE AC COMPRESSOR IF SYSTEM PRESSURE RISES TO HIGH CAUSED BY RESTRICTION IN THE REFRIGERANT CIRCUIT OR OVERHEATED CONDENSOR.MAKE SURE COOLING FAN IS RUNNING WHEN THE AC SWITCH IS ON.THE COOLING FAN KEEP CONDENSOR COOL, IF COOLING FAN DONT RUN.YOUR AC WILL STOP BLOWING COLD AIR.HAVE THE REFRIGERANT SYSTEM CHECK OUT.MAKE SURE YOUR LOW SIDE PRESSURE IS 10 - 37 PSI. THE HIGH SIDE PRESSURE SHOULD BE 112 - 210 PSI. CHECK THE AC COMPRESSOR CLUTCH FUSE AND RELAY.
Check all fuses first. if the fuses are okay, disconnect the engine cooling fan connector and using jumper wires, connect the fan motor directly to the battery and ground. If the fan still doesn't work, replace it. If the fan does work, its relay may be faulty. Check in the engine compartment fuse box for the cooling fan relays. Try switching the cooling fan relays and see if the engine fan comes on and the a/c condensor fan stops working. If so, the engine cooling fan relay is faulty. If the engine fan still doesn't come on with a good relay, then check the engine temperature switch located at the passenger end of the front cylinder head. It is supposed to switch (have continuity) when the engine temperature reaches 205 deg F. You can remove the switch and put it in a pot of close to boiling water (212 deg F). If it doesn't have continuity at that temperature, it is defective.
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.
SOUND LIKE FAULTY CLUTCH FAN OR THE AUXILIARY ELECTRIC COOLANT FAN NOT RUNNING. CHECK AUXILIARY FAN FUSE AND RELAY. IF LOOK GOOD HOT WIRE TO SEE IF FAN TURNS ON IF NOT FAN FAULTY. IF FAN RUNS YOU HAVE FAULTY THERMO SWITCH. WHICH LOCATED AT THE BOTTOM OF RADIATOR ON THE LEFT HAND SIDE OR ON THE LOWER RADIATOR HOSE ON THE RIGHT HAND SIDE OF THE ENGINE COMPARTMENT.IF FANS OKAY COOLANT LEVEL CORRECT.REPLACE THERMOSTAT.HAVE RADIATOR AND ENGINE FLUSHED.CHECK IN FRONT OF GRILLE MAKE SURE NO DEBRIS BLOCKING OFF AIR FLOW THROUGH RADIATOR CORES AND AC CONDENSOR CORES.
This could be one of many problems so it's probably best checked by someone with the correct tools and knowledge.
That being said,
With your engine cold, open your hood and start your car. Check to see if your cooling fan is engaged, take note of its speed if it is. Then turn on your AC and listen for the compressor clutch to engage. once you hear it, check to see that your cooling fan is blowing, if it wasn't before. The fan should be on and in high speed whenever your AC is on, whether the engine is hot or not. If it is not, then the reason for losing cold air is that, due to the lack of being properly cooled, your freon pressure is getting too high and is causing the compressor to turn off.
If the fan is blowing as it should be, you may have a faulty compressor or the clutch on it may need to be shimmed.
Another culprit could be that your system is low on freon or the switch that senses the pressure is faulty.
And yet another culprit could be a faulty relay that is overheating and shorting out.
Sorry I couldn't give you a difinitive answer as to what the problem is, but without diagnosing it myself, this is the best I give you.