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Strange Radiator Fan Issue Help

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My name is Rod and I need some help.

We have a 04 RX-330 that has begun to overheat when sitting. I figured It must be a fan issue.

I had my wife start the car and turn the ac up. I could feel it was getting warm and it is full of fluid.

(I checked first) Fans never came on.

Then I turned the car off and unplugged the harness where it goes into the computer thingy in the middle of the radiator, after checking the 50 amp fuse, which is good, and I have 12.3 volts there.

I unplugged one fan and had 10.9 volts there.

I am sure there is a temp sensor - I do not know for sure where this is. I wanted to unplug and see if fans ran.

Anyways I plugged everything back in, started the car, and you can audibly here a change in the motor or? Maybe it is the ac pump turning off and when it does it is warm and says fans turn on. I have no idea.

The fans never turned on on their own but get this: When I turn the passenger side or drivers side fan they suddenly begin to operate???!!!

It does not do this all the time. Only when I hear the car change tone, and you can hear thing funky little noise like a fan motor rattle but I do not think it is that because of position. It actually sounds like fluid moving thru the thermostat, maybe?

So in short heres what I have: Fuse (50A) is good. 12 volts to fan computer. 10.9 volts, (I should re-check when a fan actually runs or?) at fan plug. Fans will start with assist, only, and both run. I doubt both would go bad at same time.

Is it this small silver computer box and if so where is the best place to purchase one?

I have been up all night and am going to bed. I will check back about 3pm. I hope one of you has an idea and responds. I'd be grateful. Thank You and I hope you folks all have a great day.

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I am guessing it is this little computer box (silver, about 2-3" square and about 3/4" and it does not put out enough volts to start the fans but when I "Help" start them they have enough volts to run.

Sound plausible?

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You might want to pick up a factory service manual or at least a Haynes manual. My guess is that the thermal fan switch has failed. Typically, the switch output voltage is sent to the fan when coolant temps exceed a certain temperature. To test the switch you should know what that temperature is and be able to monitor it. A ScanGuage 2, which plugs into the OBD II port can monitor coolant temps and more that 12 other parameters.

But really, you need to know more about your cooling system before proceeding. Perhaps someone on this forum has a service manual for this vehicle and can provide specifics.

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  • 2 weeks later...

I bought new fan/controller combo for 150.00 including shipping. (actually was 146.plus change) I installed this last night and problem solved.

I would like to add I now have 2 extra fans that are fine. I could not find the controller alone.

If anyone needs a fan, right of left, let me know. I would let you have them for the cost of shipping.

The multi-meter check was what told me what the issue was. 12V gong in and less than 12V coming out.

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