2003 Highlander cooling fans

[mommucked]

180k, check engine lights on,code says the temp sensor. The gauge reads/moves like it always has and. I have noticed the fans only work when the AC is on but the gauge has never showed overheating. I'm going to drain/flush the system and replace the sensor but I think something else is keeping the fans from randomly working w/o the AC. This car hit a deer 3 years ago and did some damage to the grill/headlight etc. Is there a relay or other switch/sensor to control the fans?

 

[Fabrik8]

I don't know the specifics of the Highlander, but many vehicles have separate temp sensors for the ECU and for the temp gauge; sometimes a temp switch will control the fans, sometimes the ECU will turn the fans on. From your description, it sounds like the gauge sender is working properly, and the coolant temp sensor for the ECU may be bad. The temp sensor may be causing the fans to not turn on if the ECU controls the fans, and there is usually other circuits to turn the fans on with the AC automatically so don't get too wrapped up in that.

Change the sensor, so you know that part is working properly, and then troubleshoot the fans if they still aren't working.
In other words, you have a known fault, and something else which is likely a related symptom of that. Fix the known fault first, then fix the related symptom if it still exists.

 

[mommucked]

I don't know the specifics of the Highlander, but many vehicles have separate temp sensors for the ECU and for the temp gauge; sometimes a temp switch will control the fans, sometimes the ECU will turn the fans on. From your description, it sounds like the gauge sender is working properly, and the coolant temp sensor for the ECU may be bad. The temp sensor may be causing the fans to not turn on if the ECU controls the fans, and there is usually other circuits to turn the fans on with the AC automatically so don't get too wrapped up in that.

Change the sensor, so you know that part is working properly, and then troubleshoot the fans if they still aren't working.
In other words, you have a known fault, and something else which is likely a related symptom of that. Fix the known fault first, then fix the related symptom if it still exists.

Thanks, I found the thermo/fan switch in the bottom of the rad. so I'm gonna replace both sensors along w the coolant and see what happens.

 

[a_kelley]

It's likely the cooling fan switch. Check continuity on it in water heated on the stove if you want to verify it was bad, but it's my bet it was.

 

[mommucked]

It's likely the cooling fan switch. Check continuity on it in water heated on the stove if you want to verify it was bad, but it's my bet it was.

thanks, that was the $120 switch, as long as I was draining/replacing the coolant I'm replacing the $24 temp switch too. Been over and hour flushing the block now and then and it's about done. I ain't messing w the thermostat after finding out how much of a bitch it is to replace it and it seems to work just fine, I may try to flush the Hcore though.