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Heater blowing cold air

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Old 10-03-08, 09:43 AM   #16
lexus114
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I like the way you added: Yes the tranny was replaced at 125K.
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Old 10-05-08, 10:38 AM   #17
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I have the exact problem on my 2001 RX300. The codes I pulled are:

21
31
33
41

Let me know what you guys come up with. I've tried Auto mode full hot, manual mode full hot, recirculation button on and off, AC on and off, etc, etc. The best I can get is room temp air.
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Old 10-05-08, 12:35 PM   #18
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Volume I of the RX300 Repair manual, starting on page DI-828 has many pages of troubleshooting guide. Code 21 seems to point to the solar sensor circuit. Code 31 Is labeled "air mix damper position sensor circuit". Code 33 is labeled "air outlet damper position sensor circuit". Code 41 is labeled "air mix damper control servomotor circuit".

There is mention of pulling the ECU-B fuse in the engine room junction box (fusebox) to 10s or longer to clear the diagnostic code memory.

All the codes mention the A/C ECU as a potential trouble area.
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Old 10-05-08, 01:21 PM   #19
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Thanks Bob2200,

I pulled the ECU-B and it cleared the codes. Ran the engine again and no heat, pulled the codes again and it showed 31, 33, 41. Ran it through the self diagnostics but I don't know what is considered a fail/pass, it went 1-9 and started over.

Started the engine again and no heat, pulled the codes again and 21 popped up along with 31, 33, 41. Each time I started in Auto and waited for the fan ramp up due to the engine being cold, the ramp up occurred but with out heat then I went to manual mode, no heat.

This seems like an "ECU" nightmare for me, I'm having NAV ECU problems too...I'll start another thread on that.
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Old 10-06-08, 07:16 AM   #20
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Quote:
Originally Posted by ronl1961 View Post
As I understand it the a/c heater control panel has an electronic control unit (ecu) that monitors the systems circuit and stores trouble codes in memory. These codes evidently are stored only in the ecu and are not detected when using an OBDII code reader that was used on my vehicle at Auto Zone. I dont know if this works on all Lexus models but with my RX you can press and hold the Auto and Recirculated air switch at the same time. Wait a couple of seconds and turn on the ignition switch. The display window will flash four times and any codes that are stored in the ecu will show up on the display screen. My codes were 31 and 41. 31 = Air Mix Door Position Sensor circuit and 41= Air mix Door Servomotor Circuit. I have a complete list of all the codes if any one wants me to post them. Im assuming that the air mix door sensor some how reads feed back from the temperature control selector and adjust the position of the air mix door using the servomotor to obtain the selected temperature. So I guess what I am saying is, does any one think that it's the sensor,servo motor or both need to be replaced. Sorry,hope this didn't confuse any one.
do you hold down the buttons while you turn on the key?,or let go,then turn on key?
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Old 10-06-08, 01:19 PM   #21
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Hey Blueridge,

Have you removed the glove box by opening the door and removing the 2 phillips screws and the 2 lower 10mm bolts. Takes about 3 minutes and allows you a very clear visual look at the behavior of the 2 servos.

You can then remove the white exit vent tube and see the trap door open and close as you adjsut temp control. If you do complete this simple task, put some greese on the white plastic vent control parts.

There is a door which is almost up against the heater coil and as you will see, this door open and close to compensate for max or min heat levels.
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Old 10-06-08, 04:40 PM   #22
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Thanks RX300malib,

I guess this explains why I wasn't getting air on the floor. After removing the glove box and running the system through it's checks, etc, none of the servos are moving, not even the sound of them trying to move. I did notice two small stainless pipes that were hot to the touch, so heat is available to the core.

Also the door you referred to was closed.
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Old 10-06-08, 04:59 PM   #23
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Quote:
Originally Posted by lexus114 View Post
do you hold down the buttons while you turn on the key?,or let go,then turn on key?
Hold down buttons for approx. 2 sec. and turn on ignition switch while still holding down buttons.
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Old 10-06-08, 05:27 PM   #24
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Hey RX300malib,

I take that back, I HAVE HEAT! I figured what do I have to loose if it's broken? The arm that controls the door you referred to appeared to be shut hard. So I gently pried it open with a screw driver and it began to work!

I'm not sure how long this will last but the servo adjusts the door position with the temp **** perfectly. I did notice that when selecting the cabin temp close to the OAT, the servo moved the arm/door back and forth in very small quick increments.

Now, as for the upper arm/servo I am not getting anything, I'm assuming that is for the placement of air via certain vents? I'm only getting air through the upper vents regardless of selection from the controls.

Thanks again!
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Old 10-06-08, 06:46 PM   #25
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I did the simular to Blueridge this weekend. Removed glove box,underpanel and plastic exit vent tube. Servomotor for the air mix door was making a clicking sound. After unpluging the servomotor I was able to remove it by using an extra small and short phillips screwdriver.(top screw was hardest to remove, had to come in at angle to clear the heater core lines) After removing, I took servomotor apart by gently prying tabs apart and seperating the two pieces. Do not try to move plastic arm before taking apart or it will strip out gears inside. Need to make sure arm side is facing down when taking apart so that drive gear will not fall out. Cleaned metal contacts with contact cleaner (alcohol will work also) along with drive gear face where contacts touch. Added a little white grease to drive wheel face and snapped back together. Reinstalled servomotor and connected wiring. Checked out while dash was still out and all works well. Now have heat. Dont know how long this fix will last. I read that the servo motor gets cooked because it sets too close to the heater core lines. Thought about wrapping insulation around heater core lines.
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Old 10-06-08, 06:55 PM   #26
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Quote:
Originally Posted by blueridge View Post
Thanks Bob2200,

I pulled the ECU-B and it cleared the codes. Ran the engine again and no heat, pulled the codes again and it showed 31, 33, 41. Ran it through the self diagnostics but I don't know what is considered a fail/pass, it went 1-9 and started over.

Started the engine again and no heat, pulled the codes again and 21 popped up along with 31, 33, 41. Each time I started in Auto and waited for the fan ramp up due to the engine being cold, the ramp up occurred but with out heat then I went to manual mode, no heat.

This seems like an "ECU" nightmare for me, I'm having NAV ECU problems too...I'll start another thread on that.
Blueridge, my codes originally showed a 21 also which is solar sensor as mentioned by Bob2200 but I read in another post that you will get this code if you run the check when it is dark or if you're in a garage. You usually wont get code 21 if you're in direct sunlight unless the sensor is really bad. Try checking codes again in direct sun. 21 will probably go away.

Last edited by ronl1961; 10-06-08 at 07:27 PM..
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Old 10-06-08, 07:12 PM   #27
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Hey RX300malib,

I take that back, I HAVE HEAT! I figured what do I have to loose if it's broken? The arm that controls the door you referred to appeared to be shut hard. So I gently pried it open with a screw driver and it began to work!

I'm not sure how long this will last but the servo adjusts the door position with the temp **** perfectly. I did notice that when selecting the cabin temp close to the OAT, the servo moved the arm/door back and forth in very small quick increments.

Now, as for the upper arm/servo I am not getting anything, I'm assuming that is for the placement of air via certain vents? I'm only getting air through the upper vents regardless of selection from the controls.

Thanks again!
Blueridge, you're right about the upper arm(air outlet servomotor) I watched mine work while I had everything apart and it ports your air from defrost to vent to floor. Dont know if it is the servo motor thats giving you the code 33=air outlet door position sensor circuit. Could try tapping on it while changing flow settings to see if it's sticking.
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Old 10-07-08, 06:46 AM   #28
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Quote:
Originally Posted by ronl1961 View Post
Hold down buttons for approx. 2 sec. and turn on ignition switch while still holding down buttons.
Got it thanx.
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Old 10-21-08, 07:47 AM   #29
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I have the very same error codes (21, 31 & 41). I took my RX300 to a repair shop and was given a quote for replacement of the HVAC Control Motor - Air Mix (part no. 87106-48020). Where is this located? Is it an easy DIY job?
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Old 10-21-08, 10:38 AM   #30
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It is not that hard of a job, but patience is needed. You will need to remove the glove box, two crews on top corners and two 10mm bolts on the bottom corners. It also helps to remove the small trim piece next to the passengers left foot. There is a plastic screw on that.

I was able to fix the servos (both were inop) by taking them apart, cleaning contacts, grease, etc. I do not know how long that will last. I have priced the servos at irontoad.com for $125.61 each. There is an airmix servo and a recirculation servo, the recirc servo controls the damper for vent selection. It sounds like you only need the airmix servo.

The servo is held in place by 4 small screws and the airmix servo is more of a pain to get off than the recirc. You will need to twist your body and use a lot of patience to get to the screws and remove. If your RX has been running let it cool down, less than an inch away from the servo are the lines to the heater core, that may be why this servo fails to much! It gets hot there!

There is a wired plug that you will have to press the tab and pull out. When installing make sure you match up the servo arm position to the door airmix door position. What I did is: turned the ign switch to "on" and set the controls to full hot and let the servo move the arm. then placed it onto the airmix door arm.
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Old 10-21-08, 10:38 AM
 
 
 
 
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250, air, blowing, blows, cold, dash, duct, es350, heater, lexus, mix, remove, rx300, servo, vent

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