Cooling fan does not come on and car overheats
Tested fan relay with ohm meeter relay tested good
when relay is "jumped" fan comes on "fan motor good"
I unplugged the a/c compressor switch and fan came on as well as the check engine light. any ideas? Where is the temp sensor? is the sensor for the temp gage the same? The temp gage is working. what sensor tells the fan to come on?
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Re: Cooling fan wont work
The water temp sensor is located near the thermostat housing. This sensor is what tells the ECM to turn the fan on/off. The water temp sending unit is located near the same area. You know you have the correct sensor is because the water temp sensor has a 2 prong plug. The water temp sending unit only has 1 prong.
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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.
This is controlled by a cooling fan sensor/temperature sensor, as well as fuses, and a relay. These will have to be checked.
Make sure your coolant level is full, the coolant temperature switch won't work if the level is too low. If coolant is low, you need to find out where it went to by pressure testing the cooling system.
If it's not low and the fuses are good, the relay is working:
The fan should be tested, bypassing any sensors to make sure it is functioning properly.
The sensors can be tested to be sure they are working properly at the correct temperature with a voltmeter/ohm meter.
Reverse troubleshooting the wiring and ignition is the next step if you haven't found the problem.
The car model was not included in the question. In general if the radiator fan is not starting the first thing to check are the fuses. Depending on the car's model there is one or two fuses in line with the cooling fan circuit. If there are two fuses, then one is in the fuse plate inside the car, the other one is under the hood.
The next part to test is the thermostat. The thermostat housing is located on the refrigerant fluid lines, either near to the radiator, or near to the engine block. The thermostat can be tested using VOM tool. Read either Ohms or volts to find out if the thermostat is closing the fan circuit when the engine is hot.
Most fan circuits use also relay. Variable speed fans have often more than one relay. The fan relay(s) is often located under the hood. Relays can be tested reading volts at their contacts or swapping the relay with one of the same kind.
If fuses, relay and thermostat are OK, then the fan motor is often the next test. The motor can be tested energizing it directly. Variable speed fans have more than two wires powering the motor. To avoid risk of damaging the fan motor the repairer should refer to specific wiring diagrams before jumping fan cables. A different way of testing the motor is reading volts at fan motor while engine is hot. If there is volts at motor contacts but motor does not come on, then the fan motor is defective.
heres a little test start vehicle turn a/c on high in the defrost position your fan should start if so than test hi low fan relay and replace coolant temp sender not sensor in some cases replace both thank u have a good day.
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.
since you have already tested fan and relay and both work, the problem may be the engine temp sensor. There are two sensors. One goes to instument cluster. This is engine coolant temp sensor, the other is engine temp sensor which is usually attached to engine block, sometimes they are connected to thermostat housing with the coolant sensor. You can pully the engine temp sensor and test that sensor same way as relay. (with mulitimeter)