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Why won't my cooling fan turn on (swapped thermostat, thermoswitch, fan really)(fans work when hard wired to battery). Causes car to overheat in idle.

Swapped the thermostat, swapped the thermoswitches, topped off radiator fluid, and swapped relays around and fuses. Also hardwired fan to battery to ensure fan motors work and they do. When AC is on fans do not turn on either. Car overheats when in idle because fans won't engage. With heater on it lowers coolant temp. What am I missing?

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Depending on the year, there should be 3 relays that control the fans.
There's a rad fan relay (4 pins), an a/c condensor fan relay (4 pins), and a fan control relay (5 pins). This allows them to be run at low speed or high speed. Check the grounds behind/under the righthand headlamp.
Check Fuses 57, 58 (30 Amps) and fuse 46 (15A) under the hood, and fuse 3 (7.5 Amps) in the driver's underdash fusebox.

Posted on May 18, 2014


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Posted on Jan 02, 2017

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SOURCE: car turns on ok gets

you know the water pump for that particular car is on the other side? is driven by the cam... either your water pump is not working,(to remove water pump you need special tool) did you change the termostat? temp. sensor?

Posted on Mar 28, 2011

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check your temp sensor. It is either located on the bottom of the rad or on the block some where. It should be a two wire sensor...not a one wire(for gauge) Sometimes when the sensor is faulty the ecu will not get a signal to turn on the fans. Also try running a straight power and ground to the fans to make sure they actually work. ( Just un plug fans and use a jumper wire to the tangs of the connector)

Posted on Apr 15, 2009

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SOURCE: 1995 Nissan Sentra GXE Overheats (Temperature

are the upper and lower radiator hoses hot when car overheats? if so check for a clogged radiator or weak water pump. if one hose is hot and the other is cold or much cooler then replace the thermostat.

Posted on Aug 12, 2011

Testimonial: "It was clogged. Thanks or your insights in directing me to figure it out."

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SOURCE: 94 acura tries to overheat after reaching operating temp replaced radiator relays for cooling fans and thermo switch, new hoses and thermostat, after reaching operating temp top and bottom hoses swell

Based on what you are saying and what you have done so far you have a cylinder head gasket leaking combustion gases into the cooling system, this type of leak causes a gas bubble to form around the thermostat and then it will not work properly. Also when this type of leak is the problem there will be no white smoke out the tailpipe or coolant in the oil, the gasket only leaks on the compression stroke.

Posted on Feb 08, 2012

Testimonial: "Dennis Wei, thanks for the help on my 94 Acura, your description with the gasket leaking on the compression stroke was right on the money"

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