Margate330

For anyone following along, plz check out @cdnewton video above.

To go any deeper, one would need the skills to do some electrical troubleshooting.

If the OP is up for it I can post the wiring info with notes but I don't suspect that's an option since he has a mechanic, otherwise I'd try to help.

A switch would work but it's not ideal, and I realize the suggestion was offered as a hail Mary last resort.

OP really needs someone to dig in and figure it out! 🛸

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DamnSkippy

I’ll take the wiring info if you’re willing to share it. I’m out of the country for a few weeks, so I can’t get to this until the end of the month.

I could not find a reference to a “ Main Relay” like the YouTube video posted above. I’m not sure there is such a thing on the RX330. I guess maybe it’s incorporated into the power block? Under the fuse box. Any suggestions for a “main relay” would be appreciated. I have a salvage yard nearby that has quite a few Lexus and Toyota’s, so getting a power block is probably possible. There’s always eBay too.

This car is worth less than $1500 I’m sure, so taking it to a Lexus dealership for a bunch of troubleshooting and the parts is out of the question.

Thanks to everyone for their assistance so far. Hopefully I can get this figured out and share the information with everyone else.

cdnewton

I am not 100% sure, but the youtube part number reference equates to "Blower Motor Relay".
Based upon that, I think the RX330 equivalent is:
https://parts.lexus.com/p/Lexus__RX-...870400283.html

Margate330

Fan Ecu wiring:
(1): White(w/ blue stripe)= 0V, ground
(2): Black= +12V from Fan Relay
(3): Green= Fan Ecu control signal wire from Engine Ecu. The Engine Ecu adjusts the fans speed by raising and lowering the voltage on this wire. 0V= fans are off.


Did some tests today on the Fan ECU.

Assumptions:
(1): engine is cold for these tests

Test #1::
(1): key is off and out of the ignition.
(2): negative battery terminal is unhooked and pulled to the side.
(3): measure continuity(near zero ohms) from the Fan Ecu plug's white wire to the negative battery terminal. This is Fan Ecu ground. Good!
(4): hook up battery.
(5): measure and witness 0V on the black(power) wire, there should be no voltage on this wire and fans should be off.

Test #2
(1): battery is properly connected.
(2): key is turned all the way on but engine is not started
(3): measure and witness +12V on the black(power) wire. Good, we are getting power from the Fan relay to the Fan Ecu.
(4): measure and witness near 0V on the green(control signal) wire.
(5): fans should be off.


Test #3
(1): start car
(2): both cooling fans are off
(3): turn on AC
(4): both cooling fans are on
(5): I am measuring approx 3.3V on the green(control signal) wire.

About green (control signal) wire:
(1): no voltage means fans should be OFF
(2): voltage present, fans are ON


About fan relay: I haven't found it yet. If someone knows where it is, please let us know.

DamnSkippy

Thank you for the description and diagram. I wish I could find the FAN MAIN relay too. I suspect it's built into that power block located under the fuse box. The relays under the brake fluid reservoir do not seem to be the Radiator Fan or Main Relays. I'll let you all know what I find.