Driver side face vents not blowing

I hope this helps others that may come across the issue I had.

Last week all of a sudden the driver side vents stopped blowing on our 2017 Prius Prime 68K miles. Upon turning the car on, the AC control grayed out for a minute or so before you can control it. Diagnostic mode (push AUTO and recirculate within 5 sec) displayed the code 43. Techstream also showed B1443 Air Conditioner-Air Outlet Damper Control Servo Motor Circuit. As always, I searched PC for anything similar, and found 1 post with the same issue on Prime with no solution. So, I reviewed the manual and got some ideas from few Gen 3 posts I saw.

I tried some noninvasive ways first. Disconnected the 12V to attempt to clear and reset the car which didn't fix. With Techstream I cleared the MIL but B1443 came right back. Next, I tried initializing the motors via Utility. It runs for about a minute to complete but the code did not go away. The motor in question is the No 1 radiator damper servo motor on the driver side.

It was time to dig deeper. The repair manual says to remove the motor and manually check the dampers. It also says to connect the motor to the No 3 motor connector harness, then perform a manual test with Techstream Active Test. There was no way I was going to remove the entire dashboard as the manual says. Gen 2/3 posts and some YouTube indicated you can go through the footwell. It was tight but managed to remove the motor assembly. Here are the steps compiled from few sections of the repair manual to remove trims to get to it.

1. DISCONNECT CABLE FROM NEGATIVE AUXILIARY BATTERY TERMINAL
2. REMOVE INSTRUMENT PANEL FINISH PANEL END LH
3. REMOVE INSTRUMENT CLUSTER FINISH PANEL GARNISH ASSEMBLY (2x connectors)
4. REMOVE FRONT DOOR SCUFF PLATE LH
5. REMOVE COWL SIDE TRIM BOARD LH
6. REMOVE NO. 1 INSTRUMENT PANEL UNDER COVER SUB-ASSEMBLY (2x 8mm bolts, connector)
7. DISCONNECT HOOD LOCK CONTROL LEVER SUB-ASSEMBLY (unclip and pull out)
8. REMOVE LOWER INSTRUMENT PANEL FINISH PANEL ASSEMBLY (1x 10mm bolt, 2x connectors)
9. REMOVE LOWER NO. 1 INSTRUMENT PANEL AIRBAG ASSEMBLY (2x 10mm bolts, 10 Nm)
10. REMOVE FRONT NO. 1 CONSOLE BOX INSERT LH
11. DISENGAGE LH LOWER CENTER INSTRUMENT CLUSTER FINISH PANEL SUB-ASSEMBLY
12. REMOVE NO. 1 AIR DUCT (3 claws, 2x 10mm bolts 9.8 Nm)
13. REMOVE NO. 1 AIR CONDITIONING RADIATOR DAMPER SERVO SUB-ASSEMBLY (2x screws)

Everything was pretty straightforward but these tips may help. Make sure you disconnect the battery before. To remove the hood release you have to pry up the tab located underneath the lever then slide it out. Before removing the bolts for the airbag unit, I removed its trim. It’s held by hooks on top and bottom of the airbag unit so you’ll need to undo them. I didn’t disconnect the airbag but just set it aside. I also couldn't remove the air duct (step 12) but it would've given me more room and visibility.

With the motor out, the dampers moved fine. I separated the servo motor from the gear assembly (2 screws) then cracked it open. It was clean inside with no sign of damage or loose connection. I tested the battery with a 9V battery just to see if it moves and it did. The motor contacts looked clean so I snapped the housing back together. Tested the motor by itself without the gear assembly on the No 3 connection which is at the bottom of the radiator. The motor tested fine and all normal. If it passes the test then the manual concludes AC harness is bad and to replace it but I was not prepared to do that.

At this point I connected the No 1 servo motor to its connector and reconnected No 3 motor. Then I attempted to initialize the servo motors again with Techstream. Voila, the code cleared and I was back in business. I put it all back together and the vent mode control is working again.

removed trims




couldn't remove the air duct


good look at No 3 servo motor for the rear vents


No 1 servo motor sub-assembly with the connector off


looking straight up at the motor


removed servo sub-assembly




inside the servo motor

 

Hi sorry, I’ve been away. The issue came back 2 months later. @ColoradoBoo yes I did not replace anything because the motor worked and all the contacts seemed to be okay so put everything back. B1443 didn’t come back until few weeks ago. It’s probably an intermittent contact failure inside the servo motor gear dial thing. It was pretty greased up inside and I didn’t want to take that apart then.

This issue is causing the AC control locked up for 2-3 min after power on; not great since it’s getting hotter.

I could get a new servo (P/N 8710647200 $140 from dealer) or swap #1 and #3 servo since they are the same part to see I get a different code. #3 controls the rear vent. I will post an update, hopefully soon.

 

Update:

Finally had some time to dig in there again and removed the #1 servo sub-assembly. It was not responding at all. Here you can see the pulse is at 128 which means it's not responding at all.


When I apply power to the motor (pin 1-2) it turns so I suspect there is a bad contact inside the servo. I disassembled it.


Now I just rotated this servo back and forth by hand using the gear. It moves well enough and didn't feel anything wrong. After several turns I assembled all back together then tested with a batter to make sure it rotates.


I reconnected the servo motor by itself to the harness and let it hang while I tested. The motor moved as the car started. Techstream shows the Pulse at 256. Proceeded to Active Test.




The motor responds to pulse between 164-256.


The problem is gone at this point. Let's see how long it takes for the symptom to come back. If it does again then I will replace the servo.

 

Thanks for the info on the harness. I believe my servo has an intermittent connection problem. It’s been 2 days of driving roughly 100 mi with AC in AUTO and so far no error code.