Cooling Fans not operate in High Speed Mode - RX 330

[carlover_rx]

Hi,

i have Lexus RX 330 2005.

I noticed my Radiator/Condenser cooling fans operate only in "Low Speed" Mode in all 4 scenarios below. < Refer Attachment >

a) Engine coolant temperature 90°C (194 °F) or below - > Rotate (Low speed)
b) Engine coolant temperature 95 °C (203 °F) or above -> Rotate (High speed)
c) A/C Refrigerant pressure is less than 1,520 kPa (15.5 kgf/cm2, 220 psi) -> Rotate (Low speed)
d) A/C Refrigerant pressure is 1,520 kPa (15.5 kgf/cm2, 220 psi) or above -> Rotate (High speed)

I already checked below.

- Removed fan connectors from fan control module & directly wired fan motors to battery. Both fans rotate in high speed. -> No issue with fan motors

- Removed and re-plugged A/C pressure sensor socket. A/C compressor cut off happens in normal fashion.

- Test control pulse to fan control module. ( i.e. " Small Green wire " ). It gives 1.7v~ 2.0v for radiator coolant temp triggers , 2.5v for Air Con triggers

Any clue on whats wrong here ... Is it due to faulty fan control module ?

Do anyone have 2004 ~ 2009 RX 330 / 350 fan control wiring diagram ?

thanks.

 

 

 

 

[zieke]

My take is this, go by your temperature gauge. If it does not rise above normal during warm weather and stop and go driving, then why worry about fan speed? If u feel the engine is running hot, then it will need to be diagnosed by a dealer with the proper equipment. 

[carlover_rx]

Thanks.

but it has impact on AC high pressure side. My high pressure side ac hose got leaked near compressure due to higher temp. So ac condenser won't cool down gas efficiently. Specially when vehicle is parked and in idle mode with AC switched on. 

[RRoupe]

I have the same problem. The fans do not run when sitting with engine idle. This condition fails to keep the AC running cool. Interested in knowing what may be causing this.

2006 RX330 Canada model.

[ivtecdaily85]

Any updates? Having similar issues

[Bykfixer]

Causes me to wonder if there are cases of over pinched wires at connection points causing excess resistance to the coil in the relay that controls when the fan does what it does. 

Over pinched wires are fairly common in several manufacturers vehicles including Toyota and Lexus. 

[ivtecdaily1985]

A little back story, I bought the rx330 a few weeks ago with the issue of both cooling fans that run continuously on full blast as long as the car runs. Doesn't matter if AC is on or off. Found out that the issue was the cooling fan module. After replacement the fans only comes on after driving and letting it idle for awhile also with the AC running. The problem I now have is the fans would never kick into high speed it should kick in at 203°f . Car runs great its not overheating. The temperature gauge is spot on the middle. Just ordered a scanner with live data to make sure the gauge is reading correctly. I'll keep you guys updated if I find anything else. Sorry for the double post from earlier.

[Bykfixer]

Has the outdoor air been hot since you started having the issue? As in if nice cool air is being sucked across the cooling fins the sensors may not call for high speed fans. 

Just a thought. 

[ivtecdaily1985]

Out side temperature is high 80s to mid 90°f just got the car not long ago. I haven't a clue how Lexus cooling fan operate. Been driving a rsx type s for the past 12 years. 

Fingers crossed it's just not hot enough to trigger the high-speed.

[Bykfixer]

Well, I suppose upper 80's to lower 90's could trigger a high speed. In my Ford work truck for example during a mid atlantic winter the fan does not run very fast when the truck idles but does run briefly at times.  In spring I hear it running on days like you described, 80's and low 90's but that time of year the humidity it still lower than it is in the summer. It runs more but not wide open. 

In summer when it's 80 degrees at 6am and humidity is thick the nice lady at the Hardees drive through says "can you speak up there's something loud drowning out your voice?" ……that would be the cooling fan running wide open. 

[RX400h]

The most likely scenario that would result in the fans kicking in at high speed is during lengthy stop & go driving in high traffic conditions during high ambient temperatures.
Have you done this?

After driving in these conditions and after arriving home, let your vehicle idle for 5 minutes or so. I would think that the trigger temp would be exceeded and the high speed fans would be energized.

[ivtecdaily1985]

30 minutes at most, haven't had the chance to drive much. I would say low stop and go traffic. Temperatures are in the low 90°f. I left the car idleing for 5-10 minutes still no high speed. Going to monitor coolant temperature when my scanner arrived today.

[ivtecdaily1985]

Updates

Took a ride with the blue driver OBD2. Drove on the freeway for a few miles coolant temperature stay below 187°f.

Took the off ramp drove for a few more mile with moderate stop and go traffic. Temperature rise to 205°f. Still didn't hear high speed fans coming on. Once moving temps drop to 190°f. Outside temperature was 80°f

I Pulled over and have the car idle, after a minute the temperature rise to 208°f and drop to 185°f when cooling fan (low) came on. High speed still did not came on. 

Is this normal? Any RX owners with this issues? Thanks in advance

[Bykfixer]

Sounds like fans are getting it done without having to turn on high. 

Normal operating range is 195 to 220. If it goes to 225, then you should be concerned as 230 is when it begins to be in "over heated" territory. 

[2005_RX330]

I know this thread is old, but I've noticed similar behaviors on my 2005 RX330.

First, to carlover_rx, in your original post, where did you get that matrix for "CONDENSER FAN - ON-VEHICLE INSPECTION"?  I have the RX330 factory service manual (Lexus') and I have not found that matrix in the manual.

However, from what I have found in the manual, the operation you describe for your RX330 jibes with what I've observed on my RX330, and jibes with the operation specified in the manual.  But, it doesn't jibe with the matrix you posted.

What's notable is that

- the cooling fans run on LOW whenever the ECU engages the compressor clutch.  LOW... ONLY, it appears, when the clutch is engaged, never HIGH.

- the cooling fans run on HIGH whenever the engine coolant temp > 207F   AND   the ECU has the compressor disengaged for any reason (i.e., AC off or AC high-pressure > ~460psi; see my matrix below).

- if the AC is selected "On" (i.e., switch on the dash) the ECU will cycle the compressor unless the high-side pressure side exceeds ~460PSI; if that happens (e.g., sitting still in a parking lot on a hot day), the ECU stops engaging the compressor until the high-side pressure drops to ~370psi.

I'll summarize this with a matrix and will comment more in a follow-up posting.  The resulting operation of the AC is non-ideal, as you and I have seen.

Reference RX330 service manual "AIR CONDITIONING" pgs. AC-53 - AC-55, and COOLING  pgs.  CO-2 - CO-6.

[2005_RX330]

With reference to my post just prior (above), a problem arises when the vehicle is stationary, the ambient temp & humidity is high enough to cause the AC high-side pressure to exceed ~460psi, yet the engine temp remains <207F for a period of time.

In the above situation, what happens is:

- The ECU stops cycling the compressor because the high-side pressure exceeds ~460psi.   ALSO, the fans, which were running at LOW (see the matrix in my prior post), get switched OFF (which is an unfortunate Toyota oversight).

- The high-side pressure falls very slowly because there's no airflow on account of the fans being off and the vehicle stationary (I've shown this to myself on my own RX330, using pressure gauges on the high-side).

- Until enough time passes that the high-side pressure drops to ~370psi, the AC system is effectively suffering an OUTAGE and the cabin comfort degrades accordingly.

- Once the high-side pressure finally drops below ~370psi, the ECU will begin cycling the compressor and turn the fans on (LOW).

- IF, during the above OUTAGE, the engine temp increases >207F, the ECU will turn the fans on HIGH (see the matrix in my prior post).  This fortuitously benefits the AC by causing airflow across the condenser and lowering the high-side pressure rapidly; once the pressure drop below ~370psi, the the ECU will turn the fans on LOW (not HIGH, oddly, in spite of the engine temperature) and engage the compressor clutch; subsequently, I believe (but have not shown definitively), the ECU will turn the fans on HIGH if the clutch is disengaged during cycling activity while the engine temp > 207F (i.e., AC selected ON at the dash but ECU is commanding the compressor clutch off on account of adequate evaporator temperature).

Clearly, other scenarios which cause airflow across the condenser (vehicle motion, air currents / breezes) have the same effect as that described above.

Mull this over.  I've tried to describe the behaviors accurately but the description I've provided might be lacking.

I must add that this behavior, which I've observed and which jibes with the service manual, may be an artifact of the firmware release present in the ECU.  Toyota may have, at a later time, released an update to the firmware (and the service manual) which improves upon this operational scenario.  I have not investigated this possibility.

[RX400h]

Now that's a detailed writeup, Cb. The puzzling thing (if this is indeed inherent to your model and year vehicle) is why it hasn't adversely affected many others, unless those living in cooler climates or regularly drive mostly on the highway or most have had a software update. 

[2005_RX330]

RX400h:  Exactly... which is why I wonder if this behavior is peculiar to an ECU firmware release / model year and factory service manual release, and bears some dependency on the state of charge.  Read on...

The fact the ECU doesn't command the cooling fans to HIGH, ever, when the AC is engaged, seems like a major oversight on Toyota's part.  Yet, this is how the behavior is described in the manual (the manual's quite terse actually, if you've ever seen a Toyota manual; they're not very good as compared to factory manuals for GM or Honda) and jibes with my observations to date.

Now, I should add that if the AC system is in an overcharged condition, the "outage" due to high-side pressure > 460psi will occur under less demanding cooling conditions than otherwise.  That's actually how I discovered this behavior, back in 2019, when I serviced my own system and charged it with the maximum (according to the factory manual) 23oz of R-134a (this was during replacement of the condenser).  The "outage" as I've described in my previous post occurred quite regularly, and I mitigated the problem by bleeding off ~3oz of R-134a so as to put the system on the low end of the factory charge spec (19.4oz; see pg. AC-129 RX330 FSM).

Notably, as these systems age (and leak refrigerant) the problem becomes, I suspect, less likely to occur.

I should confer with the local Lexus dealer regarding the firmware release(s).  I have very rarely taken my RX330 to the dealer as I handle most service procedures myself (excepting recalls of course, e.g., for the leaking master cylinder).  Other owners, who may have had their similar model RX330 in the dealer more regularly, may have had a (complimentary) firmware upgrade at some point in the past or received a firmware upgrade on account of an AC complaint.

I can't help but wonder too, if (when?) presented with these symptoms, the dealers simply bled-off some refrigerant to mitigate the problem.

[2005_RX330]

I've updated the matrix which I originally posted (above) to add clarity and reflect certain other cases.

See below (sorry for the small image, it was constrained by width):

 

[RX400h]

I agree that checking with the dealership would be prudent. Please let us know what you find out.

[2005_RX330]

For the record, in the 2004-2005 RX330 Lexus TSB TC005-03 Revised, Title ECM Calibration: Shift Feeling Enhancement, they mention certain "calibrations" (what I call "firmware"). The date shown on every page of the TSB is August 11, 2003 (sic), which must be a mistake because it precedes the affected vehicles; presumably it's a typo.

Now, the revision history contained within the TSB is detailed as two revision notices, the first notice dated May 20, 2005 and the later notice dated Feb 9, 2006.

In that TSB they reference the "calibration" (firmware) by number, which supersedes prior releases and provides the "fix" which is the subject of the TSB ("shift feeling" in this case).   For my RX330, the two relevant calibrations listed in the TSB are 34874100 and 54828100.  Make mental note of these.

I connected my 2005 RX330 to Techstream and checked the installed calibrations (firmware); see the attached images.  It's calibrations are exactly those mentioned in the TSB.

So my RX330 has more recent firmware, presumably relevant to 2006 and even sometime later, but not necessarily the most recent; that's still TBD.

With regard to the fans' operation (the topic of this thread), the question still remains whether there was a  even later calibration (firmware) than that provided by this TSB that changed / improved their operation, i.e., enabled them to run on HIGH during certain times when the AC is operational.

I'll write more as I learn more.

[brucecav]

This explains, possibly, why my 2004 RX 330 operates in this way.. if the high side pressure gets too high, it cuts off the AC condenser. Strangely enough, my air conditioning works far better when I have it a little bit low on refrigerant. When I reduce the level of refrigerant to the very low end of normal, almost at the point where it says it is undercharged, the air conditioning works perfectly. Is this possible Because when the refrigerant is slightly low it reduces the high-end pressure and keeps it below the level where it would switch off? Please respond with any thoughts to this strange situation. 

Bruce