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Domenico Nelli

No Cabin Heat - 2000 Rx300

19 posts in this topic

Hi,

My wife has been telling me that she has no cabin heat in the mornings and now with winter around the corner I'd like to fix that problem. The car has about 125K on it. I was going to just replace the thermostat but the cluster temp gauge indicates normal engine temperature. I have had her mess with the different modes, put it on A/C then raise the temp to warm and it just stays cold. Anyone have this problem? Please help!!!

thx

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A roundup of the usual suspects would include the Air Mix Servo. It's one of three servos located under the dash at the center console: (1) Air Mix Servo, (2) Mode Servo, (3) Air Recirculation Servo. The Air Mix Servo controls the amount of hot air entering the system to attain/maintain the set temperature. I just replaced my Air Mix Servo for the same reason and while I was in the area I also replaced the Mode Servo. You will find a lot of discussion/instructions/pictures on replacing these servos here: Servo Replacement Info. You will find discussions on how to disassemble and clean the servo contacts but that is only going to be a short-term fix. Your best bet is to just replace the Air Mix Servo. Even if the Mode Servo is working OK now, given the degree of difficulty to access these (actually, it's not THAT difficult) I would replace it while I was in the area.

I ordered my servos from Stevnison Lexus, Frederick, Colorado (Servo Parts Listing). Their online price was a LOT less than what my local Lexus dealer quoted. I offered them the opportunity to match the price but they couldn't do it; they couldn't even get close!!

Lotsa luck. Hope this helps.

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Hi,

My wife has been telling me that she has no cabin heat in the mornings and now with winter around the corner I'd like to fix that problem. The car has about 125K on it. I was going to just replace the thermostat but the cluster temp gauge indicates normal engine temperature. I have had her mess with the different modes, put it on A/C then raise the temp to warm and it just stays cold. Anyone have this problem? Please help!!!

thx

Have her try MAX heat after the engine warms up and report back.

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Hi,

My wife has been telling me that she has no cabin heat in the mornings and now with winter around the corner I'd like to fix that problem. The car has about 125K on it. I was going to just replace the thermostat but the cluster temp gauge indicates normal engine temperature. I have had her mess with the different modes, put it on A/C then raise the temp to warm and it just stays cold. Anyone have this problem? Please help!!!

thx

Have her try MAX heat after the engine warms up and report back.

She did adnd it didn't work. I had her do all the combinations with the A/C on then heat max then changed the mode selector ....ugh....I read about some air/mix servo that could be impeding one of the doors/diverters not opening....

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A roundup of the usual suspects would include the Air Mix Servo. It's one of three servos located under the dash at the center console: (1) Air Mix Servo, (2) Mode Servo, (3) Air Recirculation Servo. The Air Mix Servo controls the amount of hot air entering the system to attain/maintain the set temperature. I just replaced my Air Mix Servo for the same reason and while I was in the area I also replaced the Mode Servo. You will find a lot of discussion/instructions/pictures on replacing these servos here: Servo Replacement Info. You will find discussions on how to disassemble and clean the servo contacts but that is only going to be a short-term fix. Your best bet is to just replace the Air Mix Servo. Even if the Mode Servo is working OK now, given the degree of difficulty to access these (actually, it's not THAT difficult) I would replace it while I was in the area.

I ordered my servos from Stevnison Lexus, Frederick, Colorado (Servo Parts Listing). Their online price was a LOT less than what my local Lexus dealer quoted. I offered them the opportunity to match the price but they couldn't do it; they couldn't even get close!!

Lotsa luck. Hope this helps.

thx file horse. i read that the air/mix servo may be the culprit. Now all I would need is the P/N.... I have been getting the clicking behind the glove box for years now....and kinda just turned the stereo up....so i may replace all of them... thx again!

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Hi Filehorse, maybe you can help me out here. I did a prior post about that clicking noise and no heat and was told the "servos". I got to the first one, i guess that would be the airmix and simply can't remove the second one just behind it, where the two pipes are... my problem was the clicking and no heat. after removing and cleaning the air mix servo, the first and easy one to remove. for now, i have no noise and I get very light heat at Max temp. before i put my glove box back, do you think replacing this first servo would give me max heat, or is the heat controlled by the 2nd one, (which I can't get to). all my vents are giving good air output and always did. the a/c works great, just very low warm air from heat. any suggestions would be appreciated.

bett

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If I remember correctly, the servo you are having trouble removing is the Air Mix servo. The easier one is the Mode Servo (floor, vent, defrost, mix). The air mix servo is the one that actually allows air to flow through the heater core and into the cabin. I was able to remove my Air Mix servo through the use of a thin screwdriver and probably a little "flexing" of the water supply/return pipes. It seems that I was "closer" to getting the screw driver head to engage more on one side of the pipe than the other so I approached from that side to flex the aluminum water pipe - CAREFULLY. The screws are seated in the plastic housing and don't require that much torque to loosen and once you get it started out it comes easily. Once I made the decision to "get it out or bust" the servo screws came out with little effort and there were no adverse effects (read: leaks) from flexing the aluminum water tubes as required. The tubes were not flexed sufficiently to impart a permanent bend; just a temporary displacement to allow the screwdriver to do what had to be done. NOTE: when the motor is warmed up, if you feel those aluminum tubes and they are HOT, in all probability the only source of your problem is the Air Mix servo. If you look at that servo and run the cabin temperature setpoint from Minimum to Maximum and there is little or no movement of the air mix servo positioning arm, the likely culprit is the air mix servo.

Hope this helps. My advice is worth everything you're paying for it. :rolleyes:

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If I remember correctly, the servo you are having trouble removing is the Air Mix servo. The easier one is the Mode Servo (floor, vent, defrost, mix). The air mix servo is the one that actually allows air to flow through the heater core and into the cabin. I was able to remove my Air Mix servo through the use of a thin screwdriver and probably a little "flexing" of the water supply/return pipes. It seems that I was "closer" to getting the screw driver head to engage more on one side of the pipe than the other so I approached from that side to flex the aluminum water pipe - CAREFULLY. The screws are seated in the plastic housing and don't require that much torque to loosen and once you get it started out it comes easily. Once I made the decision to "get it out or bust" the servo screws came out with little effort and there were no adverse effects (read: leaks) from flexing the aluminum water tubes as required. The tubes were not flexed sufficiently to impart a permanent bend; just a temporary displacement to allow the screwdriver to do what had to be done. NOTE: when the motor is warmed up, if you feel those aluminum tubes and they are HOT, in all probability the only source of your problem is the Air Mix servo. If you look at that servo and run the cabin temperature setpoint from Minimum to Maximum and there is little or no movement of the air mix servo positioning arm, the likely culprit is the air mix servo.

Hope this helps. My advice is worth everything you're paying for it. :rolleyes:

Not what I wanted to hear, but I'll try again to pry out that nasty screw and think i'll just replace the servo rather than doing maintenance on it. thanks.

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I agree with your approach. If you are going to go to the trouble of removing the Air Mix Servo then I would replace it. After I replaced both of mine I did disassemble the servo and you can 'clean' the contact surfaces but I think the problem is more with wear than with dirt. I suspect any fix obtained by "cleaning" the servo could be short-lived and then you'd have to go through ALL this again to install the servo that you'll wish you had installed when you had it out the first time.

Just go easy and use your good judgment on getting those screws out. It really isn't as hard as it looks but it could require a trip to the tool monger to get the right screwdriver and that would be money well-spent.

Let us know how it goes.

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Hi,

My wife has been telling me that she has no cabin heat in the mornings and now with winter around the corner I'd like to fix that problem. The car has about 125K on it. I was going to just replace the thermostat but the cluster temp gauge indicates normal engine temperature. I have had her mess with the different modes, put it on A/C then raise the temp to warm and it just stays cold. Anyone have this problem? Please help!!!

thx

I would move to Southwest Florida. We have very few complaints regarding no heat down here. Otherwise, get her a Duraflame log and a pack of matches. That should keep her plenty warm in the car.

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I agree with your approach. If you are going to go to the trouble of removing the Air Mix Servo then I would replace it. After I replaced both of mine I did disassemble the servo and you can 'clean' the contact surfaces but I think the problem is more with wear than with dirt. I suspect any fix obtained by "cleaning" the servo could be short-lived and then you'd have to go through ALL this again to install the servo that you'll wish you had installed when you had it out the first time.

Just go easy and use your good judgment on getting those screws out. It really isn't as hard as it looks but it could require a trip to the tool monger to get the right screwdriver and that would be money well-spent.

Let us know how it goes.

well I FINALLY got that air mix servo out!!! .. before I removed it, i checked to see if all the movement was there, and it is. before i buy the replacement I just want to be sure.... even if there is movement with the handle going up and down when told, it can still refuse to give hot air???? because it seems operational and I'm wondering if i'm not getting heat and its due to something else. rather spend the money on what I actually need... thanks.. I know I've been slacking with my repair.. but now that its starting to get cold, I need to move on this...

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If the aluminum water tubes to the heater core are getting hot as the motor warms up, the only thing that could prevent hot air from entering the cabin would be a mechanical blockage of some type. I suspect what you are seeing is only a partial movement of your old Air Mix servo and not full-range operation. That was what I was getting on mine. Unless there is a squirrel nest in the duct work, I think it has to be the Air Mix servo. I guess it is possible that the signal that controls the servo could be faulty but I've never heard of anyone having that particular problem without other symptoms. I'd suspect you might have display issues if that controller had failed but just guessing here. Given the age of the OEM servos and the known prevalence of this particular problem, I'm putting my money on success if you replace the servos. Be sure the servo is correctly connected to the linkage. It's pretty obvious but you can install it incorrectly. Don't ask me how I know.

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If the aluminum water tubes to the heater core are getting hot as the motor warms up, the only thing that could prevent hot air from entering the cabin would be a mechanical blockage of some type. I suspect what you are seeing is only a partial movement of your old Air Mix servo and not full-range operation. That was what I was getting on mine. Unless there is a squirrel nest in the duct work, I think it has to be the Air Mix servo. I guess it is possible that the signal that controls the servo could be faulty but I've never heard of anyone having that particular problem without other symptoms. I'd suspect you might have display issues if that controller had failed but just guessing here. Given the age of the OEM servos and the known prevalence of this particular problem, I'm putting my money on success if you replace the servos. Be sure the servo is correctly connected to the linkage. It's pretty obvious but you can install it incorrectly. Don't ask me how I know.

thanks for that, just wanted to be certain as most posts indicate movement issues.. I'm ordering the part now.. if anyone else is interested.... i found this site .. the cost for air mix servo is $152.00 with free shipping..@ www.mylexparts.com. I'll update after installation. thanks.

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Good price on the servo.

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I found out after two of my posts were lost that it is impossible to post a picture as links (e.g. Photobucket) cause the reply process to freeze...

The servos are similar in that they use a small motor to spin a worm gear. The worm gear can slip after a lot of use. This happened to my air direction servo. Roughing up the motor shaft to allow the gear to not slip fixed it. The heat/cool servo died on mine, but the gear was fine here... The motor had essentially died. Searching on the internet turned up a vendor in England that had one the same size and operating at 12 volts. And at approximately $8 shipped, it is far cheaper than replacing the servo! I will report back when the motor arrives and let you know if it works,

Just an FYI... Be sure to replace the motors exactly as they were removed as they are polarized! And try to keep the actuator arm right were it was so that it will operate the damper door properly!!

Sorry I could not post any pictures.

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I removed all three servos, disassembled them, cleaned them with solvent and contact cleaner, reassembled and reinstalled them. That was two years ago and they have preformed great with no issues. Took about 3-4 hours. A best practice prior to doing any of this is to get pictures of everything before you start and during the procedure. Always good to document everything prior, during, and post.

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That's one of the great things about digital cameras and cell phone cameras. The ease with which one can save a picture of something. I totally agree with michaelbmike, in fact that is why I was going to post pictures of the servos.

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If the aluminum water tubes to the heater core are getting hot as the motor warms up, the only thing that could prevent hot air from entering the cabin would be a mechanical blockage of some type. I suspect what you are seeing is only a partial movement of your old Air Mix servo and not full-range operation. That was what I was getting on mine. Unless there is a squirrel nest in the duct work, I think it has to be the Air Mix servo. I guess it is possible that the signal that controls the servo could be faulty but I've never heard of anyone having that particular problem without other symptoms. I'd suspect you might have display issues if that controller had failed but just guessing here. Given the age of the OEM servos and the known prevalence of this particular problem, I'm putting my money on success if you replace the servos. Be sure the servo is correctly connected to the linkage. It's pretty obvious but you can install it incorrectly. Don't ask me how I know.

thanks for that, just wanted to be certain as most posts indicate movement issues.. I'm ordering the part now.. if anyone else is interested.... i found this site .. the cost for air mix servo is $152.00 with free shipping..@ www.mylexparts.com. I'll update after installation. thanks.

Was wondering of an update? I am still on the fence if i break down and buy the servos before i tear it all apart, or just try cleaning/readjusting the mechanicals....

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