[John119]

Greetings to all,
Does anyone know the location of the rear blend door actuator for the HVAC system. My rear air temperature will only blow cold air regardless of the setting. If anyone knows what panel I need to remove to find the actuator, I would appreciate the information.

Thanks
John

 

[fibber2]

You can practically touch the rear HVAC unit when you've got the door for the jack handle open. That entire rear quarter panel has to be removed.

 

[John119]

Wow, that was incredibly helpful. Thank you so much. And the blend door actuator? is that what I am seeing in the picture at the bottom right?

 

[romualds]

Keep in mind that heating works only when air is blowing from the bottom openings and cooling-- from the top ones.

 

[fibber2]

The front and rear systems work on somewhat different principles. In the front water flows thru the heater core all the time, and a servo controlled flap directs air either thru it or around it. The rear has fewer flaps but has a servo controlled valve on the hot water line as shown in the diagram below. The air outlet control sends air to either the floor duct or the roof vents, but whether the air is hot or cold is determined by the freon flow (AC on) or the water valve (labeled 'airmix valve).

 

[John119]

Gentlemen, thank you guys for your extremely helpful and quick responses. If you will humor me with just a couple more questions before I tear into this.

1. From reading #4, I received the impression that it is only possible to get heat from the bottom vents. That the middle and upper vents were for cool air. So I could only expect heat from the lowest vents. Am I understanding this correctly? Is it true that you cannot get hot air from the upper vents?
2. I have the 2004 Sienna XLE, any chance one of you might know the part number of the 'servo control flap', 'air mix valve' and 'air outlet control'?

Thank you guys a bunch for the time pictures, and illustrations.

John

 

[fibber2]

My 12 year old says that heat can come out of the roof vents too. If I get a chance in the next day or two I'll try to confirm that.

There are not a lot of parts for the rear system sold separately. My understanding is that the rear heater core and the air mix valve (water valve) are one assembly called the rear radiator subassembly. Maybe an AC/radiator shop could separate them and sell you components.

 

[CaptainBDSC]

I think I have the same but opposite problem in my '05 XLE. The system blows mostly hot air; much hotter than the target temp. If I turn the AC on and turn rear temp to maximum low, air out of the vents goes down to 68 at best and that's even now in thee winter with it 40F outside. From what I read above you are saying it is unlikely I can fix just the blend door?

 

[mathmanbill]

Is there a reason why the photo bucket pictures are blurred and I cannot properly view them? I’m having the same issue as the original poster.

 

[Roader]

Is there a reason why the photo bucket pictures are blurred and I cannot properly view them? I’m having the same issue as the original poster.

Photobucket extortion. You'll find a clear but smaller version of that picture here:

sienna rear heat valve - Google Search