My daughter has my hand me down 2005 RX330 with 213K Miles on it. A few nights ago she was sitting at a drive through when the car overheated and started spewing coolant (from the overflow reservoir tank). I met her and could see that the radiator cooling fans that I had replaced about 18 months ago were not spinning. Upon examining the fans I could smell a burnt odor coming from the fan ECU module (which was replaced at the same time as the fans - replaced as a built assembly with the shroud). Sure enough, the Fan Control Module was fried inside. I ordered one from Amazon, because Autozone did not have one in stock and it would be quicker and about 1/8 the price from Amazon. The new module arrived. I swapped it in. I thought that it was odd that the cooling fans came on right away as soon as I plugged the new fan control module in, because the car was cold. I started the car and refilled the coolant, and the car operated normally, and the fans switched on once the AC was selected on. AC Blows cold. When the AC was turned off, the fans turned off until the coolant temp got warm, then they kicked on. The car did not overheat, so I shut it down and noticed that the fans kept running. I thought it was fine because the car was still warm. I packed up and a few hours later I got a call from my daughter stating that her battery was dead. The cooling fans ran until the battery died. Thinking that perhaps the cheap Amazon ECU module was defective, I located another module at a local auto parts store that cost $120 more than the Amazon one. That ECU Module exhibits the exact same behavior as the Amazon Module. I bought a temperature sensor and unplugged the connector on the one installed in the car and plugged the new sensor in without installing it (thinking if the original sensor was bad, I could maybe diagnose it this way without removing it). No change, so I put a meter on the old Temp Sensor and got what looks to be a valid resistance reading compared to the new cold sensor. I have called a mechanic shop that I trust, but he cannot get to the car until Monday. I loaned my OBDII scanner to a friend who is out of town until next week. I ordered a replacement OBDII Scanner from Amazon and will scan the car tomorrow. There is no CEL on.

Here's the wrap up:
- Car overheated when the aftermarket cooling fan ECU Smoked.
- Replaced the cooling fan ECU and the fans operate normally and car and AC work like they should.
-When you turn the car off the cooling fans kick on (even if they were off) and will run until the battery dies.
-When you start the car, the cooling fans will turn off until you turn on the AC or the car warms up (operates normally).
-Replaced the replacement ECU with another locally purchased one, and the problem persists.
-Tested the Temp Sensor by plugging in a new one (not installed but grounded to the block). Also checked old and new Temp Sensors with Ohmmeter.

Has anyone else encountered a problem like this with any vehicle? I loaned my newly acquired Lexus NX to my daughter for the weekend, and I'd really like to get it back from her.

BTW, I'm new here. I have owned 7 Lexus Vehicles since 2005. 2002 IS300, 2005 RX330, 2005 GX470, 2008 IS250, 2013 RX350, 2017 RX350F, and a 2021 NX300 The cars get handed down to my kids.

 

Until someone with experience with this issue chimes in, try searching for "fan relays" for your model. They can malfunction and cause problems on many cars, not sure about RX330.

 

Thank you. I'll search for the fan relay.

UPDATE. I searched for the relay and it seems that if there is one at all for this fan, it is the part that I have replaced twice (The Engine Cooling Fan Module).

If anyone knows if /where there is a cooling fan relay on the RX330, I'm interested in knowing. Thanks.

 

Hi friends,

When I replaced my cooling fans with aftermarket I realized some important things.

After market kits that include the fan module: these kits include the fans and power module. HOWEVER, they may not be compatible with the OEM fan power module. If your cooling fan kit included the module, you must use that same module. The motors are different than OEM and that's why they include the module.

Aftermarket kits that do not include the fan power module: these are ok to use an OEM style module to run them.

Note: I tested both types with my oscilloscope to find out why. One kind uses a voltage that rises linearly as fan speed rises. The other kind uses pulse width modulation to control fan speed. Long story short, fan kits that include the module will not run on the oem module. At least on the ones I tested, completely different style motors even tho they look the same.

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Thank Margate. That is good information, and it make sense. I bought the radiator cooling fan kit from Amazon, It was manufactured by Dorman, and I see that it has a limited lifetime warranty. I will order another assembly and swap out the module that failed, then try to get Dorman to warranty the module. I will try to reach out to the seller to see if I can buy a module from them. The whole radiator assembly with fans and the Module cost less than I just paid for a module from Autozone yesterday. Thanks for the tip. BTW, the Dorman module that failed the case actually popped open. Inside on the circuit board I was looking around and the center wire is labeled PWM** So it seems it uses Pulse Width Modulation.

 

Do you still have the original Toyota OEM fan controller? I recently replaced my fans with a TYC 621110 that does not come with a controller, so it is compatible with the OEM module, which I reused. This combo works great -- properly turning on and shutting off. (The original Denso fan motors were caked with a black dust from the internal motors breaking down)

If you are certain that the fan controller ECU is fine with the aftermarket fans, then the AC Amplifier maybe at fault -- that unit also controls when the fans turn on.

 

Unfortunately when I replaced the whole cooling fan assembly, I tossed the OEM control module. Probably not the smartest move, but in a previous life I had a 3 car garage with a lift. Now live in a 1 bedroom condo. It’s not all bad though. On the ocean and don’t have to mow grass or shovel snow.

 

My first cooling fan set was made by Doorman.
It came complete with fans and power module.

Here's the scary part.

It was defective right out of the box and almost overheated my engine.

When starting the car cold after installation, both fans kicked on.

Weird and not right because AC was off and engine was cold.

So I got suspicious and plugged in my scanner and monitored my actual temp in F in real time.

When my engine temp got to approx 206f degrees, the normal approx temp for fans to come in, these fans turned OFF! Lol

Another words, both fans running full blast until car gets up to temp and then they shut off, exactly opposite of how they should work.

That's why I lost complete faith in the kits with included modules.

I bought a different kit with no included modules and installed my OEM module and it's been running well for a few years now.
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Ps, can I please make a recommendation to anyone following along. Buy the kit that does not include the power module and reuse your own module.

For OP, since you just bought a module I'd shop local for a fan kit to install it on. And pick up a spare OEM module on eBay for dirt cheap to keep in the trunk under the flaps for an emergency spare.

I DO NOT recommend kits with the cheap throw away module included. Mine was defective right out of the box, plus engines are expensive so I really don't want to overheat it! Lol

 

Great 411, Phil......

 

Update May 6th. I ordered a new Dorman Radiator Fan Assembly. I took the Cooling Fan Controller off of it and connected it to the currently installed radiator fan assembly. It exhibited the same problem as before. It works normally until you turn the car off, then the fans run at high speed. Just to be completely thorough, I reinstalled the Cooling Fan Controller on the newly purchased assembly and plugged it in without installing it on the radiator. The new assembly (fans and all) does the same thing as the currently installed assembly. I got a new bluetooth OBDII scanner and I have OBD Fusion with the Lexus module. I didn't have any DTC codes and the PIDS are pretty limited for a vehicle that old, but I can see that the temp sensor is operating normally. Hopefully a high dollar Snap-On will be able to see more data. My shop is open today so I took it in this morning. It's past closing time and they haven't called back, so I don't know if they have made any progress on it.

 

Alright! I took it to my local trusted mechanic. He's the guy that isn't going to charge me 5 hours for diagnosing a problem only to tell me that he doesn't know. I spoke with the tech who worked on the vehicle yesterday and he was at a loss. He suggested (Just like Margate 330 - hat tip!) that maybe I should try an OEM controller. He said if he got one from Lexus and that wasn't the problem, that he could not return it, and it was very expensive. So, I made a pilgrimage out to my local Pick N Pull and grabbed the nicest one I could find off of a Lexus ES. I checked and it's the same Denso Part number. Plus, this one was actually very clean. As I feared, this control module exhibited the same symptoms. Works normally until you turn the key off, then fans run on high (like full speed high - higher than when the A/C kicks in it seems).

So, back to the drawing board. I'm thinking about putting a relay on a toggle switch that my daughter can use to turn the fan off when she shuts the car off. I know, it's pretty redneck, but the car otherwise runs fine to get her back and forth to work.

One last thing that I realized when I was driving it home from the shop. Last year, I installed an aftermarket radio (Apple Car Play with the Metra Dash Kit). The aftermarket dash kit from Metra included a resistor so that the Climate Control system would still work. I can confirm that without the resistor, the Climate Control would not work. I don't know why this would even affect the radiator colling fan (and I suspect it isn't) but I'm throwing it out there. FWIW, the Climate Control and everything else on the car works perfectly fine.

RECAP:
- 2 aftermarket Engine Cooling Control Units installed. All exhibit the same behavior - Work normally until key is removed from ignition. Then fans run full speed until battery dies.
- Temp Sensor checked and replaced with and aftermarket temp sensor. No Change.
-OBD II No DTC's Everything looks good.
- Purchased another entire Dorman radiator cooling fan assy. Fans, Shroud, Controller. No Change.
-Took it to a trusted shop, and they put an aftermarket Cooling Fan Controller on it (3rd one now). No Change.
- Went to the junk yard and procured a newer looking OEM Denso Fan Controller. No Change.

At this point, all I can think of is to rig a switch with a relay to manually turn the fans off after the car is shut down. My shop recommended a battery disconnect, but I don't think my daughter will want to deal with not being able to unlock her doors and losing all the stereo and window setting, etc.

Any suggestions welcome. Thanks in advance.

 

Have you checked the engine main relay?
No idea if this is even close, but worth a try?

 

Well, this video describes my daughter's car's symptoms to a T. Thank you for sharing that. I had done a search for the issue, but was probably being too specific in my search and would have only gotten returns on a Lexus RX. I will give that a try and report back to the group. I'm feeling a little a optimistic. Thank you.

 

Hi, You could wire in a simple 3 pole HD 12V Relay.
It's a fairly easy Temp Fix.
1.You'd disconnect the wiring connector on the Radiator Fan Switch
2. Use the Ground Out terminal( pin)on the OE Rad Fan Switch and run a correct size wire to the -Minus terminal on the New fan Relay,
Use a Diode in the wire to prevent feedback.
3. Run a wire from a +12v source, that's always Hot, to the + Positive terminal on the New fan Relay.
4. Run a wire from the +12v Out terminal on the New fan Relay to the +12v connector on the fans, use a HD Diode in the direction to the Fans.
Ground the Fans to the Chassis.
5. When the Radiator Fan Switch reaches temperature, it will turn on the Negative pin on the Fan Switch completing the circuit to the the New fan Relay and the fans will come On and go Off Automatically.
It's Just Another suggestion, it beats having a girl, to remember to flip a toggle switch to get the fans to work!
Good Luck with getting it fixed ✅️

 

This is Not isn't a Perfect Solution by any means, and I'm Not sure how this will work, if at All, with the the Lexus Stereo System, and the fans may Not come on Automatically when the A/C is turned On, they will come on when the coolant gets to the required temp.
PS- Do Not Hook up the OE Connectors back up to the Radiator Fan Switches on the Radiator, leave them disconnected.
Like I said it's only a Suggestion until it can be Repaired Correctly .