Dual zone climate control passenger side temperature issues

dooby73 · Oct 13, 2019

Like the title says, 2016 Limited and right side stays on full heat no matter what.
I’m assuming it’s an electric motor failure for the temperature setting.
Would anyone know where this would be located? Is this a common issue?
Tia

Fibber2 · Oct 15, 2019

I don't have the diagrams for the RAV4 specifically, but most Toyota HVAC systems follow the same basic design and many share components.

The his-&-hers heater has a split plenum and separate air-mix dampers to keep left and right air blends apart. You are basically regulating how much system air flows thru the heater core at the lower section of the HVAC box before heading to the mode damper (floor/vents/defrost).

If you have heat on all the time just on one side, something is amiss with either the Servo controller, the motion arms off the servo, the damper shaft, or the flaps attached to the shaft that route air into the heater core. If it's like other Toyota's, you can probably remove the glove box door and maybe the lower dash panel and get to the servo body.

Other issues that it could be:

Most Toyota's have gone to CAN buss, and each servo in the system (there are up to 4) has a microchip that's sync'ed to the HVAC Amplifier (the brain). It could have lost communication and need to be re-initialized, the chip in the servo could be bad, the wiring could be bad, or the Amp or front panel control could be bad.

dooby73 · Oct 15, 2019

Wow, thank you very much that’s great information.
Regarding the canbus, would pulling the ground on the battery possibly reset the servo & controler? That would be the easiest thing to try first.
If that fails I’ll manually try to move the servo or damper to see if that changes anything. If all else fails I’ll get a replacement servo assuming I can find the exact location. I did have the glove box out and did see a servo, I guess that might be the one I have to check.
Thanks again

Fibber2 · Oct 16, 2019

With the glove box out you can probably get to two different servos. The one on the 'fan box' will open/close the fresh air / recirculate air flap. Operation of that one should be pretty obvious. The other one to the left mounted on the main box will be the heat module.

Where this gets tricky.... Some Toyota models have the Mode solenoid on the drivers side, some on the passengers side. In applications where it's on the passengers side they may have a DOUBLE SOLENOID assembly. So you'll find a two pot module that runs both the passenger's heat (the lower one) and the mode flaps (upper one). Yes, double the trouble to remove and get the little arms back into place. You want to make sure this is really bad before you mess with it! Feel for it doing something while moving the dash controls.

Resyncing the system seems to also fall into two camps. Some have done the battery reset (disconnect, step on the brake pedal to thoroughly discharge, wait for 20 minutes, reconnect) and replacement servos came on line. Recently someone on the Sienna board mentioned that a menu in Techstream was required to get it going.

dooby73 · Oct 20, 2019

Ok well I just looked into this and the servo is working when adjust the temperature control.
I’ll have to try and peek Inside to see what is wrong. At least now I know it’s something mechanical and not electrical.
Thanks

Dual zone climate control passenger side temperature issues

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