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#4450384 - 07/05/17 12:21 PM Sienna rear A/C only works from rear controls
Huie83 Offline

Registered: 02/19/09
Posts: 469
Loc: Minnesota
First summer with our 06 Toyota Sienna that I picked up last year.

I just discovered that the rear A/C blows hot if I try and control it from the front HVAC controls for the rear. If I switch the front HVAC for the rear to "Rear" to allow the rear A/C to be controlled by the controls in the second row, the rear A/C will blow cold and functions as normal. It doesn't have auto climate control or anything, just manual dials.

I've been doing this for a few weeks but it sucks if my 3 year old is back there and I have to stop to reach into the 2nd row to turn the fan up/down etc.

Any ideas? I've never had to diagnose a split A/C system before and especially such a weird issue where the A/C functions good but only for the rear from the 2nd row.

#4450671 - 07/05/17 06:43 PM Re: Sienna rear A/C only works from rear controls [Re: Huie83]
Ethan1 Offline

Registered: 12/29/14
Posts: 1620
Loc: 'murica
Sounds like the front heater controls are bad, but it would need some testing. A capable scan tool will tell you what position the computer thinks the controls are in, which could quickly find your problem. It would also tell you if there are any body codes regarding lost communication with the front HVAC controls. Other than that, gotta bust out a wiring diagram and DVOM, start pulling dash trim apart, etc

#4451241 - 07/06/17 12:11 PM Re: Sienna rear A/C only works from rear controls [Re: Ethan1]
wag123 Offline

Registered: 06/14/11
Posts: 795
Loc: Texas
The body computer controls this.

#4455947 - 07/11/17 07:41 AM Re: Sienna rear A/C only works from rear controls [Re: Ethan1]
Huie83 Offline

Registered: 02/19/09
Posts: 469
Loc: Minnesota
Thanks for the insight. I'll have to see if I can get my hands on a scan tool to take a look around. If it ends up being too much work, I'll just leave it be.