Radiator fan always ON

[David*All-Trac]

Corolla 4AFE 1997

I’m trying to figure how to fix my ‘’always running rad fan’’. As soon I turn the key to ON (without starting the engine) the fan start to spin.

I’ve made some search here and there and this my results :

• Check continuity on fuse 33 (FAN) and fuse 34 (CDS) : OK (fuses located under the hood)
• Check is there Voltage in the temp sensor wire : Test light ON
• Test the temperature sensor: look OK
• .

• Now, what else?

I need to test the fan relay but I do not have the procedure in my hands. I need someone to give me this procedure.

Obviously, I want to fix this problem but, since this car is my 500$ Corolla winter beater, I have simply unplug the fan connector and I will use the car like that. It is the winter after all !!

But... but, If I can find the problem come from rad fan component I’ll be more comfortable. Comfortable because I will know that have nothing to do with the temp sensor and since the temp sensor is related with the E.F.I. that will not affect (not to much) the MPG

[Bitter]

isn't there also a fan switch on the circuit?

[David*All-Trac]

Originally Posted by Bitter

isn't there also a fan switch on the circuit?

Nice shut.Yes you'r right. I did some research, again, and I believed this probe was for the dash gauge.

So...I did not test the coolant fan switch... yet.

But the switch is a ''one pin switch''. How should I test it. What resisistance ohm / temp ?

Someone with the Toyota FSM can find this info.

Merci.

[Bitter]

its open until a temp, then it closes. so if it's always open or always closed then it's bad.

[David*All-Trac]

Good, I'll check that soon.



I still need the fanrelay test procedure.

[REN69]

did you bother to check your thermostat first?? usually the fan will run when the thermostat fails, replace that first, cheap and easier to do than hacking wires away... if that fails, replace the temp sensor... if that fails then hack away.

90% of the time is a bad thermostat.

[Danny289]

Originally Posted by REN69

did you bother to check your thermostat first?? usually the fan will run when the thermostat fails, replace that first, cheap and easier to do than hacking wires away... if that fails, replace the temp sensor... if that fails then hack away.

90% of the time is a bad thermostat.

Nice post which save lots of money! I would like add somthing to that " replacing radiator cap if its seals is bad " . above post is rule of thumb for overheating but not in this case ( assuming the thermostats is a usual thermostat not a safe-failed one). Car on ==> Fan immidiately on before Thrmostats opens====> close circuit all the time===> problem in circuit===> sensor or relay problem(IMO)

[David*All-Trac]

Yep, the thermostat is on the list since I have also a CEL P0125. But that CEL there since I bought the car (a month ago) and the fan problem is there since last week.

I also know that code can be link to a bad O2 sensor.... but without catalytic converter...

Anyway, I'll change the thermostat some day... if that fail... that's it ! Thermostat is a 10$ - 13$ job. Temps sensor is much more... too much for my winter beater.

[Danny289]

Originally Posted by David*All-Trac

Yep, the thermostat is on the list since I have also a CEL P0125. I also know that code can be link to a bad O2 sensor.... but without catalytic converter...

Anyway, I'll change the thermostat some day... if that fail... that's it ! Thermostat is a 10$ - 15$ job. Temps sensor is much more... too much for my winter beater.

go for safe-failed thermostat it is a little more expensive but it worths around~$ 20

I was thinking if you need a little fun can spend around ~ $ 5 and add simple manual switch off and on loool. but if your fan is not working and you don't have any overheating problem I doubt even your car has a thermostat. or maybe it ihas safe-faield one which is open to eternity .

[Bitter]

one from the dealer is like $17 and worth it I think.