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Discussion Starter #1
Recently my climate control has been acting up. The first thing I noticed was that between drives, my climate control was set to off even if I had turned off the car with the climate on. It usually would remember the last setting. The second issue was that sometimes the climate control would be "frozen" for about 30 seconds to a minute when I started the car. Pressing any of the climate buttons or rotating the knobs wouldn't do anything. Eventually, the the climate control started working and I could turn on the climate control and adjust temperatures like normal. These 2 things were irritating, but easy to look past because everything kind of worked.

Today, I noticed that the rear climate was blowing very hot air (even when set to max cold) while the front was blowing cool air. Outside temperature is about 75 and I have set the car's climate control to 70 auto. I think this problem is related to the above 2 issues.

First thought is that it is an electrical issue having to do with a bad sensor or maybe a bad climate control panel. Before giving it to a mechanic, I wanted to see if it's something I could fix myself. What should I be looking for or try first?
 

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This is a common problem. The servo for the temp blend door that controls the air flow is bad. The ones that control the front temp is at the bottom of the center compartment. The driver side one is easy to replace, however the one On the passenger side one is blocked by the blower housing and needs to tear the dash apart to replace. When you start up the car, the HVAC system is testing all the signals from all the blend doors. If it doesn’t get a good signal from one. It will wait. An ultimately time out. This is the reason why when you start up the AC does not work right away because it’s waiting for the signal test. Since it’s the rear that is blowing the wrong temp, it may be the one for the rear, which I don’t know exactly where it’s located.

 

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What year van, and what model?

Are you seeing any unusual digits on the display? Some systems can display error codes on the panel, but you may have to force it into diagnostic mode to retrieve them. As stated above, a blend door (it's all CAN today) could do it. Or the AC Amplifier (the brain, located behind the glove box) could be bad. This is one case where proper diagnostics up front could save you a ton of unnecessary work and wasted money.
 

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Discussion Starter #4
This is a common problem. The servo for the temp blend door that controls the air flow is bad. The ones that control the front temp is at the bottom of the center compartment. The driver side one is easy to replace, however the one On the passenger side one is blocked by the blower housing and needs to tear the dash apart to replace. When you start up the car, the HVAC system is testing all the signals from all the blend doors. If it doesn’t get a good signal from one. It will wait. An ultimately time out. This is the reason why when you start up the AC does not work right away because it’s waiting for the signal test. Since it’s the rear that is blowing the wrong temp, it may be the one for the rear, which I don’t know exactly where it’s located.

This is exactly what I was looking for. Thanks for the information. I found a helpful video (
) that covers critical parts of the rear HVAC system. The system is located in the rear passenger side area. Another videos (
) shows the actuator on a Sequoia which may be helpful. The first video mentions a bad expansion valve could be the issue. Is there a way to tell if the expansion valve could be the issue in my case vs the blend actuator?


What year van, and what model?

Are you seeing any unusual digits on the display? Some systems can display error codes on the panel, but you may have to force it into diagnostic mode to retrieve them. As stated above, a blend door (it's all CAN today) could do it. Or the AC Amplifier (the brain, located behind the glove box) could be bad. This is one case where proper diagnostics up front could save you a ton of unnecessary work and wasted money.
2013 LE, FWD

I'm not seeing anything unusual on the display. This is really helpful information. What is the best way to diagnose the issue properly? Is there a way to get into a diagnostic mode to retrieve the codes?
 

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I had this problem but, mine was heat on driver's side when calling for cold. i could see the actuator(servo) wasn't moving so, I replaced it. Still didn't work. Disconnected the battery after reconnecting IT WORKED! and that was over a year ago. Try that first it's cheap!
 

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Discussion Starter #6
Good suggestion. I'll give the battery disconnect a shot and see if that works. I also have access to another Sienna; I can swap the actuator from there and see if it that fixes it.
 
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