Gary79

posted this in OT couple days ago, some help over there, but no clear answers so here I am posting "out of category". facts, 97 toyota rav4, ac, auto, 4wd, 70k. the a/c & defroster are off, the cooling fans run as soon as you turn the key over and run all the time. the temp gauge works fine, although a little slow to heat, because the fans are running all the time. I unplugged the wire to the temp sensor on the block and the fans kept running. any help appreciated. I rebuilt my 79 vette, but this stuff drives me nuts, i don't enjoy newer cars, too many bells and whistles and everything is connected to something else, etc, etc! tia.

Boofers

Just a guess, hard to say without schematics - The temp sensor is most likely read by a microcontroller (uC) which then sends the temperature information to other circuitry. uC's are not powerful enough to drive fans so the control signal from the uC is sent to a fan driver circuit, most likely a pulse width modulated (PWM) circuit.

The fans being stuck on could be a broken wire between the uC and the PWM circuit. It could be a problem with your PWM fan driver circuit. It could be a problem with a uC. These days there are upwards of 30+ uC in a single car! Mechanics talk to your car via computers and usually they can tell what the problem is like if a uC is fried.

As with anything - the more complex something is the more there is to go wrong... Good Luck!