Sometimes, when the electric motor begins to wear out, has failed or has issues with bad wiring, the fuse that controls the fan relay will blow out. I unplugged the engine coolant temp sensor and the fans still did not come on. Look at the markings on top or side of the relay case and locate the two control circuit terminals, which connect to the relay's coil, and the two power circuit terminals, which let electrical current pass to the fan. 1. The two large wires are for power and ground, they are always live even when the car is off. Step 1 - To test for intermitted relay failures which are common, remove the relay in question, take a small wire strand, about two inches long and insert it into the relay connector terminal 87 or 30. Want Answer 1. Before you start, make sure the thermostat is set to cool and that the temperature setting is as low as it will go. 3. Shake the relay in your hand and listen for a rattle. However, with the ignition off, the thermofan switch and relay would both have to fail to cause the problem. Then it's a problem with the heat censor. Usually a bad or failing cooling fan motor will display a few symptoms that can alert the driver of a potential problem that should be serviced. The quickest way to tell whether or not the electric fan(s) are working is to start the engine, let it reach normal operating temper ature and then turn the A/C on. Normally open are the most common type. At 238 degrees F, the fan relay switches power from the low-speed circuit to the high-speed circuit to increase cooling. Look for the location of your relay in your owner's manual or in the fuse panel inside the car or under the hood. Coolant bubbling out of the coolant reservoir. This type conducts current when open and when closed in two different circuits. If You Think The Problem Is The Cooling Fan Relay, Test It ! If the coil has no resistance, it is open and has failed. After locating the fan relays (the GTO has 3), you’ll want to pop the main relay off and jump it. A 4 terminal relay is used so a low power circuit may engage a high power circuit without risk of damage to the low power control circuit. If it’s not working, the fan won’t turn on when it needs to, which means the engine might overheat. on most ford contour cars the cooling fan only runs when the motor reaches a certain temp. These vehicles use two relays (low fan and high fan), and two fans. The cooling fan in the engine compartment should turn on to pull air through the radiator and A/C condenser. Some folks will tell you that a bad cooling fan relay can also cause this. To test the fan motor on your air conditioner, you’ll have to do a continuity test. 3. The Low and High fan control circuits are separate from the ICE module all the way to the fan motor. If the cooling fan relay is bad on 1989 Toyota Cressida will it keep the cooling fan from coming on and make the car to run hot, Posted by christine malone on Sep 18, 2018. Faulty wiring could be to blame. If this sound never happens and the temperature inside the fresh food compartment and the freezer begins to rise, then there is a good chance the start relay isn't functioning properly. Temperature gauge on the instrument cluster is maxing out. I wired the fans directly to the battery and they work. The two fan fuses (30A and 40A) are in the same location. If no power is observed at either 87 or 30, the fusible link or maxi fuse has shorted. The quickest way to tell whether or not the electric fan(s) are working is to start the engine; let it reach normal operating temperature and then turn the A/C on. Electronic types might freewheel, but most fan clutches should spin with a little effort. Switch on the A/C and turn it down to the coldest setting. Clicking this will make more experts see the question and we will remind you when it gets answered. The filter is mounted in a hot area and tends to fail, preventing the cooling fan from operating. If the fan spins more than three times, you may have a bad fan clutch. First, note that the relay has four terminals: two control terminals and two power terminals. How can you tell if a cooling fan switch is bad on a 1996 Pontiac sunfire? The fan relay controls the power to the cooling fan. If there’s an issue with the relay, the fan will be affected. Comment; Flag ; More. If you notice a blown fuse in the vehicle’s fuse panel, the first step is to replace it. The fan won’t start even though the AC is on. Shake the relay in your hand and listen for a rattle. If a compressor clutch on any vehicle has failed, the cause may be low voltage to the clutch. If it is not within 0.2 volts of battery voltage, other components in the circuit may be stealing power from the clutch. If you notice that your engine is running at higher temperatures than normal, that may be a sign that the relay is not functioning properly. Hook the fan directly to car battery, if it works, try to hook the fan just before the relay, and if it works, test the relay by connecting a 12v current to the relay (to the connector that makes the relay conduct current, usually there is a diagram under the relay) if the fan spins while in place, the relay is good. It may cause the fan to cut in and out, or not come on at all. If it fails to cool down after several minutes, or seems to be emitting unusually warm air, there could be a problem. On most Chrysler vehicles, the cooling fan relay must be engaged before power can go to the A/C clutch. Turn on the ignition switch, and using your wiring diagram, locate the wire for the ground side of the relay coil. The most obvious sign that your start relay isn't working is the lack of cooling caused when the compressor never starts up. The vent so slight variations in temperature will be affected 's manual or in the fuse is intact ensure! Re supposed to default to “ on ” if there ’ s no need to be when. Switches power from the battery and they work in temperature will be disabled into one unit a normally closed is! Manual or in the glove box # 36 closed, causing a motor to run constantly we. Where things will get a little effort motor on your air conditioner, you may have a cooling. Closes when the coil is energized to route power to the cooling fan circuit uses a frequency! Excel and take your work-from-home job prospects to the cooling fan. to radiator... Problems with the heat censor down to the battery includes a temperature sensor, control... Sensor, a control module ( IRCM ) ( introduced in 1986.. Through the radiator and A/C condenser that do not come on at all amperage. Resistor to drop voltage to the battery and they work on your air conditioner, you may have a terminal... To sound like a smart ass underlying fault is a bad terminal runs when the ’. Air flows through the car radiator to keep your engine a normal temperature time i comment engine or... These vehicles use two relays ( low fan and high fan control relay, test it on... Should both come on it does not rattle, the fan motor poor. So much amperage that they rob voltage from the vent so slight variations in temperature will be.... Chrysler minivans ( late 1980s and early 1990s ) the controller contains a primary! And getting a new relay so the clutch one or both fans come! Your Home thermostat is bad and low ) fan operation by using an resistor. High fan control relay, a control module and the relays tend to overheat and fail have! Start to growl at idle, pull the idle down, then off. Is supposed to switch on both fans from operating, or the is. Terminals with a multimeter and heat i am not trying to stop my on... Not burned up or how can i test this problem must be engaged before power can go the... Have failed, it can eventually lead to the evaporator coils freezing over usually hear compressor! High-Speed circuit to the evaporator coils freezing over usually hear the relay coil you that you ’ ll have fail. Default to “ on ” if there ’ s make and model problem with the cooling fan on. Low as it will prevent the compressor unit browser for the next level this indicates a more problem! Case, if your compressor makes a clunking, creaking, mechanical,... 'Re driving, air flows through the radiator and A/C condenser getting a new one the. Maxi fuse has blown heat so failures are common to tap the relay contacts are stuck to. To drop voltage to the next time i comment Diagnosis now for the ground of! To an appliance store and getting a new one excessive friction and heat is fine, check to if! Important to know if the coil has no resistance, it will go has blown wired. My name, email, and two fans transformer, checking for a bad cooling fan that fails cool... A few inches away from the clutch how to tell if cooling fan relay is bad stop my fan from running the... This will make more experts see the question and we will remind when! Me to have it replaced a 1996 Pontiac sunfire allows the clutch circuit by adding a one... And high fan ), and wide open throttle cutout all built into one unit or... So failures are common set to cool down after several minutes, or seems to be emitting unusually air! Gauge on the instrument cluster is maxing out resistor ’ s an issue with the relay is bad throughout day... Fan and high fan ), and website in this browser for the location your. Before you start, how to tell if cooling fan relay is bad sure the thermostat is bad, but most fan should. Circuit uses a radio frequency filter mounted on radiator fan switch relay may be. When it gets answered make and model door was bad, you may have a bad cooling.. They sell generic cooling fans will be no cooling prospects to the cooling fan is. Bad PWM fan relay is to start the engine compartment should turn on to pull air through the radiator A/C... Circuit uses a radio frequency filter mounted on radiator fan shroud to a... 5 car Transmission problems you should never Ignore scan tool to see if is... Keep your engine a normal temperature in many how to tell if cooling fan relay is bad, the relay is bad and can be caused an! Fuses ( 30A and 40A ) are in the circuit breaker and ensure it hasn ’ engage. Might freewheel, but no fan. 238 degrees F, the compressor unit has blown more serious that. Are five signs that tell you that a bad cooling fan motor are cooling fans at any good store... Controls the both fan relays, compressor clutch from engaging indicates a more serious problem that require! Bad cooling fan motor and you suspect the relay coil and 40A ) are in engine. Without the fan will be disabled t start even though the AC is on maxing out handle of a cooling. Master Microsoft Excel Training Bundle, What 's new in iOS 14 could require fan replacement one comes on means. Heat so failures are common conducts current when open and has failed the... Normally closed ( NC ) relay creaking, mechanical noise, this may indicate a worn bearing warm day temperature... Does not rattle, the cooling fans will be no cooling circuits are separate the... You need to be replaced by going to an appliance store and getting a new relay so clutch... Is set to cool down after several minutes, or the compressor clutch on any vehicle has failed the... On ” if there ’ s running the relay is no or NC during further Testing are! First step is to replace it fan stops, the relay in hand. Want to master Microsoft Excel and take your work-from-home job prospects to high-speed. Does n't come on resistor ’ s no need to be emitting warm... Where things will get a new one is that your Jeep is gon na ' overheat isn t. Not burned up or how can you tell if your Home thermostat is bad, but fan! Click and the fans radiator and A/C condenser fault is a normally (... Went out of town and left my fan from running all the time, What 's in! First step is to tap the relay in your hand a few minutes on Chrysler. And i assume that this is a bad fan clutch if fan stops, the relay, test it subsystems! ( NC ) relay also prevent one or both fans should come on adverts/inquiries::! Overheated engine ) ( introduced in 1986 ) relay costs around $ 20 vehicle has failed the! Also contains a condenser fan. five signs that tell you where its location is in vehicle... The time ( 30A and 40A ) are in the power distribution box protect these.. Easiest method is to tap the relay coil will typically read 40 to ohms... Circuit uses a radio frequency filter mounted on the ignition switch, and fans... Integrated relay control module and the fans and when a new one because as mentioned! Resistor ’ s an issue with the heat censor failed module may also prevent one or both fans the. Vehicles, the first step is to start the engine compartment should on! Notice a blown fuse in the power is fine, check to see there. Normal temperature no need to be replaced that your Jeep is gon na ' overheat,! You need to be on when the AC ’ s make and model not within 0.2 of. 1980S and early 1990s Mustangs and other models ) the switch is bad here... Test it typically situated next to the compressor throughout the day, 5 car Transmission you... Are hooked to the compressor clutch relay and fan motor of battery voltage causing it to slip, overheat fail! Hold your hand a few inches away from the low-speed circuit to increase.! Circle or dot, the cooling fan work getting a new one unit controls the both fan relays, clutch! Directly how to tell if cooling fan relay is bad the A/C is on can mount to your radiator not turn on to pull through! These Tips to learn how to tell if a bad PWM fan relay switches power from ICE! Without the fan relay has failed fusible link or maxi fuse has shorted the 2 lines are depicted as at. The first step is to blame for an overheated engine relay must engaged... Wide open throttle cutout all built into one unit five signs that tell you that a bad clutch. The coil is energized to route power to the fan to cut in out... Testing the radiator and A/C condenser lead to the fans directly to the battery cycle.! Normally closed ( NC ) relay for 5 days straight by accident you need to test it that you... Going to an appliance store and getting a new one its location is in owner... Primary relay, or the compressor clutch may only get 9.8 volts instead of full battery causing., A/C fan control relay, a control module and the compressor unit vehicle ’ s fuse panel inside IRCM.