car rav 4 2003 - is overheating tempt too hot-it only corrects when ac switch is turn on-help!?

fan motors are activated by two separate switch and circuit,

they can switch on-off at the same time without any malfunction effect to one another.

when you turn ON your AC , the electronic thermostat beneath the glove compartment at the side of AC evaporator housing will send signal to the ECU - then the ECU will trigger "ON" the AC-fan relay you see at the fuse box on your engine compartment.. take a look.. it is labelled..

when the engine is running without the A/C switch ON or not in operation, the "thermo switch" will be the one to activate the fan motor circuit to trigger "ON" your fan.. it has separate relay,, labelled as "RAD fan"

"thermo switch" as sometimes called by other car manufacturer as "water temp. sensor"

they work the same but looks different,

thermo switch activates the fans directly via relays

water temp sensors activates fan by sending signal to ECU ,then the ECU send signal to fan relays..

complicated ? right ? this is for genuine technicians to work on..

i am just giving you idea how system works and why some mechanics find it hard to trace trouble.

not for you to know all.. anyway.

now, look at the bottom level/cover/housing of your radiator..

if you see wires plug on to it.. it uses thermo switch

if non, your engine uses water temp.sensor.

replace it..

also, check all fan relays, fuses, and ground contacts,

sometimes it is ground (negative ) contact/fuse/relay you are missing,

do it first before changing the switch/sensor.

It sounds like either you thermostat is stuck or broken. If the fan comes on with the A/C kicking than that only really leaves the thermostat or the sensor.

There is two temp sensors in that car. if the one that controls your radiator fan is bad it wont turn on the fan that cools the car. when you turn on the AC it automaticly yurns on the radiator fan

Your primary fan may not be working. When you turn you A/C on, the secondary fan kicks on and cools the radiator coolant.

coolant temp switch is likely bad. this is the one that closes to complete the circuit to the main cooling fan.