TechnoGeek

2006 RX400H, 114K miles.

A/C started getting intermittent when car was sitting still in traffic, and then two days ago, the wife could not get the windows to defog on a rainy day (A/C not working at all).

She idled it for a loooong time (keeping the engine running). and drove it slowly around the parkling lot. Then it overheated big time (it blasted all the coolant out of the overflow reservoir). Once it cooled, refilled the coolant, tested for leaks, drove the car home, no problem, AC working perfectly, temp gauge needle perfectly in the center, runs like new.

Having two problems at the same time is confusing,

Am pretty sure the root cause of BOTH the AC and overheat is neither cooling fan is working. I have the FSM, repair TVs for fun, and have been working on cars for 30 years.

The timing belt/water pump was done by Lexus about a year ago, and no coolant needs to be added. (I changed my inverter coolant recently myself, but I digress).

Tests done so far to get those fans spinning:

1) The FSM says to disconnect the coolant temp sensor and turn on the ignition, and that should start the fans...no go.

2) The FSM also says to short two of the pins on the AC pressure switch. Two of the pins shorted should start the compressor (that worked) and the other two should start fans (that did not).

3) I connected a code-scanner that can do live data and watched the ECT to see if fans come on at 207F.....they did not.

4) There are no DTCs set, no blown fuses.

Next step is to start tracing circuits back to the ECU.

Yes, there is a question here!

1) First of all, each fan has it's own ECU....do those fail often?

2) It does not look like there is a DTC for the cooling fan circuit..should there be one?

3) Are failures of the Hybrid Vehicle ECU common on these cars?

Since there are two fans with two relays, and two fan ECUs, the problem would logically point to a something that controls both of them (the Hybrid ECU)...no?

The only 'clue' here is that I had the whole dash/console apart about a month ago. Installed a Belkin AirCast and Vaistech Aux module. Maybe a connector got bumped under the dash?

The A/C issue, I believe, is just that with the fans not working, the high-side pressure trips the pressure switch and shuts off the compressor if the vehicle is sitting still. I hooked up my AC service gauges and (holy bleep) the high side was about 440psi. (I assume this should have set a DTC, not sure why that did not). I hooked up the gauge set since the sight glass shows bubbles, which normally indicates low charge. Not to ramble here, but without fans running, that's the sort of high side pressures that are normal...well normal for when your fans are not working.

TechnoGeek

To reply to my own post.....

After many diags, believe it or not BOTH cooling fan motors were shot.

The issue was not that the fans had burned out, the issue was that that carbon dust from the brushes had filled the body of each fan motor. The Drivers side motor would work just fine once I dumped what looked like a cup of (conductive) carbon dust from the motor, the passenger side motor ALSO would run after I blew a lesser amount of dust out of it.

I replaced both motors, of course, and now it all works 100%. Have been watching ECT with a scan tool, watching live data, and its working 100% as designed.

Couple of tips for those geeky ones here:

The service manual has two mistakes, near as I can tell:

1) The book says the fans will come on with the CTS (coolant temp sensor) unplugged with ignition on. That's not true. The car has to be in 'ready', and it takes about 20 seconds for the car to 'boot'. THEN the fans come up (or don't, in my case, originally).

2) The book also indicates the fans come on when coolant temp hits 207F, with AC off. That's sorta true, but it appears that is only WITH ENGINE RUNNING (not just 'READY', but with the IC engine running.

So with the car at 210 F coolant temp, but engine off, fans are off. Blip the throttle (to start engine) and fans come on, and stay on until coolant temp drops below 207. I assume this is because heat is only generated from engine when it's running or mine has some other fault I am not aware of. I assume the fans are off since it would generate vibration/noise in this case.

Of course both fans should, in all cases, come on when the AC compressor is running, regardless of temperature. Before replacing both motors, my fans were not doing that.

FYI I traced the whole fan circuit to/from the ECM...now am an expert on that!

HtownBlue

Watch your plastic connectors coming from the fan ecu going to the fan. Those have a tendency to wear out and come loose IN THE CONNECTOR not the connection itself.

Replaced both fans in mine as well.

txshan130

Does anyone have the section of the maintenance manual for this diagnostic procedure for a 2004 RX 330?

I have the same problem...neither fan comes on and AC goes out when car is at idle..

Going to check the fans out first but need the rest of the info!

Thx,
Brian

HtownBlue

It's your fans. There is no diag procedure needed. Replace the fan motors and check the connectors and problem solved.

txshan130

Thx for the quick replies! Looks like the condenser fan motor is definitely bad...seems hard to find the DENSO p/N 1636320280 fan by itself so might just replace the whole assembly with both fans and motors...

Guessing not a bad idea since we're in TX and the car has 118,000 miles. The other one is probably on it's last legs too...

HtownBlue

OEM replacements will work fine friend. Just go slow when removing the fan housing and air intake scoops. Be mindful of the radiator too. Go slow and steady. I think you can do the whole job with a 10mm socket IIRC. Post back when you solve the issue. Good luck and let us know how to help.

txshan130

Pulled the whole fan assembly and ordered a whole new one from Amazon for $130 shipped...will report back after I get the new one installed...



OTE=HtownBlue;8095825]OEM replacements will work fine friend. Just go slow when removing the fan housing and air intake scoops. Be mindful of the radiator too. Go slow and steady. I think you can do the whole job with a 10mm socket IIRC. Post back when you solve the issue. Good luck and let us know how to help.[/QUOTE]

news1213

Hey txshan,

I'm having a problem with the cooling fans on my wife's 2004 RX330 myself. I know the problem is either the wire or the motor. I wasn't able to fix the wire part itself but I took it to a garage to get it analyzed anyway (and because it's hot in TX and my wife wants the AC to work asap..).

So the garage says it's the fan motors and wants to replace it with a whole unit for $490 including labor! I found full units for $130 like you, so I was going t ask how hard this DIY is, and what other parts I might need. I've done suspension work on my 2005 IS and do regular services to both cars. I would need to get the repair manual of course, but would you say save the money and just do it, or too much of a hassle without the right tools?

Thanks!

txshan130

Takes only about 10 min to pull out the old one and another 10 to put in the new one. No special tools required. Go for it and save the money. East fix....our AC works great now!

news1213

Cool, thanks - I took the car back home and ordered the part already. Will try and tackle it next weekend.

Jogee

Hi Technogeek or anyone else who can help me... I also have a 2006 RX400h and found out from my local repair shop that I need to replace both fan cooling motors, both fan blades and possibly the assemblies too. They're telling me the only place they can get the parts is direct from Lexus for almost $900 which seems crazy. Is there any chance you could either tell me what part numbers I need or point me to any kit that would include all the parts? Just hoping for a little help if you're able to provide it. Thanks in advance if so.

NateJG

Impressive diagnostics by those folks back in '13.

Try sending them a personal message (click on their userid).

neelnaik

Don't bother getting it from the dealer. Just order an entire new radiator fan assembly from Amazon. It should be about $120 for the whole thing. If you are handy at all, the entire job can be done with a 10mm wrench and about an hour of your time. The fan assembly itself is only held on with 4 bolts (one in each corner). However, you do have to pull the intake piping from the front of the car to the filter box, and you have to pull off 2 or 3 plastic covers on the underside of the vehicle. Like I said, it takes about an hour to do all said and done. I've had to replace it on mine. I have a 2004 RX330 and I had to replace mine at about 140,000 miles.

smassey321

One of my fans started making noises so I removed them to see what was going on. As others have posted, the motors were full of black dust. I took one apart and the brushes are worn completely down. The commutator also had a deep groove from where the very uneven brushes were rubbing. And finally both bearing ends looked very worn.

2 new OEM motors are on order. Hybrids use something different than the non hybrids so I did not want to risk the Amazon deal. Hybrid fan motors are the same for each side but the fan blades are not so take pictures or notes before you start removing them.

As bad as these were, I wish I had changed them when I had the radiator apart a couple of months ago at 120k miles.