I have a puzzling 98 Toyota Avalon 3.0L .Over heating tested for HC in antifreeze test was negative. When ac is turned on both fans come on let run for a bit the highspeed fan will kick in.If you turn the key on and unplug the ect the fans do not come on.The radiator is hot at the upper radiator hose but move down the top of radiator its ambiant temperature or close to it.Most likely a restriction in the radiator but the puzzling issue is why are the fans not coming on when ect is unplugged. Scanner readings indicated while running the sensor was reading 217F unplugged was reading -40. Without the ac on I could not get the fans to come on at all. Anyone ever run across this? Any suggestions would be greatly appreciated. I know that the 3.0 have had issues with radiators and ect sensors.

SOURCE: 1998 toyota heating problem

You need Freon gas.

SOURCE: 1994 2.2L toyota camry radiator fans do not work

Hi.....

The Normal Temperature Range to the Fan Start is: A/C ON 181 F.
A/C OFF 199 F. When the Engine Reach this Temperature the Fan should start.

OK. Do this simple test.
1---- Start the engine, Desconnect the ECT Switch located on the Radiator,
See if the Fan come ON. If yes, if not go to step #2
Connect the ECT SWITCH and leave the car Running and with a Temperature gage.
See the temperature, if the Temperature go more than 199 F.
Turn the Engine OFF.
Disconnect the ECT sensor and check for Ground at the WHITE/BLACK wire.
If ground exist, Replace the ECT switch.
But if not. Check the wire for any damaged, and the ground at the Front Left Fender.
Repair as need.

2---- check the Fuse link RDI FAN . 30 amp.
Check the Fuse link CDS FAN 30 amp.
Replace if need.
And Return to step # 1.
Check the Radiator fan Relay, Rad fan relay 2 and 3. Replace if need.

Ok. I hope this help on your question.
I can give to you the WIRING DIAGRAM of the Fans, But I need a E-MAIL adress to do that.

Thank you for use fixya....

SOURCE: bypassing Temperature sensor on the radiator

Just connect the two wires that are connected to the sensor which will keep the fan running when the ignition is on.

SOURCE: I have a 1999 Toyota Camry (4 Cyl). It comes up

The sensor for the fans is in the rad at the bottom. T-stat may be bad or the rad may be clogged. Cooling system needs attention.

SOURCE: Recently the radiator on my 2000 Toyota Avalon

Sounds like the thermostat isn't opening, or you have a cracked head or bad head gasket and it is adding too much heat to the system.