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Im assuming your refering to #8 on GMpartscenter.net theTemperature Mode Valve Actuator Assembly. Which they are two of them. One on driver side and another on passenger side area?
Number 8 I believe, is the Temperature Actuator, maybe also called a blend actuator, and it makes sense that there are 2 of them so both occupants can adjust the temperature to their liking. For those chasing the Mode Actuator as I am, it's the one that decides where the air flow should be going, it looks like #9 fits the bill. I can attest to removing #9 from under the driver's side with everything out of the way and, after removing the Driver side blend Actuator first, and also the relay panel that hangs down near the brake pedal, it's in the way. But damn! once you get it off by removing the two 5.5mm screws, it's a friggning nightmare to get the new mode Actuator back into position and get those 2 tiny screws in place and line it up. This guy explains just enough but barely. Listen to him 3-4 times, the camera angles underneath are not great.
It's obvious to me now, after struggling upside down, the guy in the video is a journeyman technician and likely has had many dashs out so he knows them like the back of his hand and every move he has to take to replace the mode actuator without removing the dash, keep this in mind. When you are a tech and work on specific cars multiple times, you know them inside and out, I was a tech once upon a time and was able to bypass the suggested methods for faster flat rate times. For me, never having any access under or behind the dash every part and location is new to me as it would be to you, and you have to figure out the best combination of tools to remove each component. Having a 5.5mm swivel socket and straight with a few different ways to get to those tiny 5.5mm screws is important. When you can't see them, it's hard to find the hole, and they easily fall. To stop that I used some sticky sound deadener to stick them to the socket and the hole they go through, so they don't fall. You really need patience to do this upside down.
What a learning experience, it's too bad that no one has said anything much about the mode actuator cam. Do you know what it is? Once you get the entire Dash removed and have access to the center vent area and the mode actuator you can pull the actuator away from the cam plate and find that there are two doors inside of the HVAC suitcase controlled by this cam. If you try replacing the mode actuator from underneath what nobody tells you is make damn sure it doesn't move to the side and out of the hole and try to follow the actuator as you pull them apart, hold it in place somehow with something when you pop the old actuator off. If you don't the cams get out of sequence on both doors and you cannot get them back into place unless you pull the dash! The white cam plate cogged snout should never get farther out of the hole than flush with the outside edge, if it does by more than about an 1/8th inch it's possible one or both arms from the Mode doors will come out of the cam slots. I' attached a couple of pictures and later I hope to write up more detailed instructions in a new how to post.
This is exactly how your Cam's cogged snout, as I call it should look, it's dead even with the retaining plate, not sticking out as I found mine after not knowing it could move and then having to completely remove the dash to get to it and get the cam back in sync again.
Last edited by Gnarley Z51; Jun 1, 2025 at 09:11 PM.
Im assuming your refering to #8 on GMpartscenter.net the
Temperature Mode Valve Actuator Assembly. Which they are two of them. One on driver side and another on passenger side area?
Well we getting ready to find out lol. As soon as i find the reference material for pulling the driver side dash area apart. Just in case i have to pull that side apart as well. Then im going to start with the passenger side dash area. Because thats where all the noise is coming from. I'll start pulling it apart until I trace it to where the noise is coming from. I already have partly pulled the passenger side dash apart some before. So I'm dreading it. But so far 15 torque bit. And 5mm 7mm tools is what was needed so far. I don't know if it will require any more tools beyond that besides plastic trim tools. But we cross that road when I come to it. I'll try to take pictures and add more reference material for this thread here. Hopefully it will help others that has had same issues and researched to only find very little information on this subject.
Reference #8 This is Temperature Mode Valve Actuator Assembly
@Allen650HP The funny thing I see in the exploded view of the parts is that the locations don't match my 2016, I'd think every C7 would be the same, if they are, then the exploded view is wrong. From what I can see in the image you supplied is #10 and #11 cam plate and housing should be right next to #9 and on the left side, as they certainly are not on the right side! I think another exploded view with actual locations would help others as they struggle to ID the failed component.
What a learning experience, it's too bad that no one has said anything much about the mode actuator cam. Do you know what it is? Once you get the entire Dash removed and have access to the center vent area and the mode actuator you can pull the actuator away from the cam plate and find that there are two doors inside of the HVAC suitcase controlled by this cam. If you try replacing the mode actuator from underneath what nobody tells you is make damn sure it doesn't move to the side and out of the hole and try to follow the actuator as you pull them apart, hold it in place somehow with something when you pop the old actuator off. If you don't the cams get out of sequence on both doors and you cannot get them back into place unless you pull the dash! The white cam plate cogged snout should never get farther out of the hole than flush with the outside edge, if it does by more than about an 1/8th inch it's possible one or both arms from the Mode doors will come out of the cam slots. I' attached a couple of pictures and later I hope to write up more detailed instructions in a new how to post.
This is exactly how your Cam's cogged snout, as I call it should look, it's dead even with the retaining plate, not sticking out as I found mine after not knowing it could move and then having to completely remove the dash to get to it and get the cam back in sync again.
Gnarley, so you're saying that even with the black plate (pic 3) holding the cam on, there is still enough play on the inside that the cam can be pulled out up against the black plate and release the door arms from the cam slots?
Gnarley, so you're saying that even with the black plate (pic 3) holding the cam on, there is still enough play on the inside that the cam can be pulled out up against the black plate and release the door arms from the cam slots?
Yes, it's actually a little sloppy! The actuator seems to push the cam into its housing and it's tight enough it all stays together. Now, if you try to remove the actuator it literally will pull the cam part way to the housing, about 3/16 of an inch away from the armrs of the mode doors and just enough that the arms will fall out of their slots and you're done, now you have to pull the dash off to get the cam back in place.
I think it's possible to hold the cam against the suitcase while pulling the actuator off by using a thin screwdriver and pressing it on the base (hub/snout) in the center to prevent it from staying attached while you are sliding the actuator off of the cam.
Had I known this I may have been able to replace the actuator without pulling the dash out. But I was able to repair the shrinking leather around the defrost vent.
Once you are finished, be sure to short your battery terminals together for 30 seconds to kill the memory, this seems to force a relearn of the HVAC and be sure to have all your sensors connected.
C7 Corvette Mode Door Actuator replacement (blowing on defrost and floor only)
Starting with GnarleyZ51’s posting May 31, 2025 on the C7 Corvette Forum. All of his statements are correct. Thank you for posting your work. It was invaluable to me.
I am replacing the mode actuator, which is above the blend actuator. I am doing all this work from below in the drivers side. I am not removing the dashboard. I am not removing the front seat (although your preference).
To kick this off, I watched a section of this U tube on removing the trim on either side of the knee bolster. Then there are three 7 mm screws in the knee bolster before you can pull it out. See C7 corvette dash removal – step by step procedure
- To provide access room, remove the 4 wire connectors and the terminal block using a T27 torx socket for the 2 screws next to the steering column.
- Remove the left footwell plastic duct (two 5.5 mm screws)
-->Note: Use a silver “marks a lot” to label the bottom side of the next parts before removal. Mark one screw post and a tab on the actuator or part. I had to go by pictures afterward, and it would have helped in reinstallation to know the orientation of the parts.
- Remove the lower temperature blend actuator to get better access to the AC mode door actuator which is above it. Two 5.5 mm screws. Mark it’s orientation prior to removal.
- I did install a pen (as a spacer) between the wiring harness and the dash support so that I could see the work area better.
- I used an LED lamp above the gas pedal, and I also wore an LED headlamp.
- Note: There are 2 ways to access this tight space. Thru the floor vent square hole, and next to the wiring harness. See the 2 photos. You can position yourself to use either location and some jobs work easier from either hole.
- The front 5.5 mm or (7/32) screw on the mode door actuator is the most difficult to remove. You will need to use a ¼” drive breaker bar. A ratchet has too large of a head to fit. This is very time consuming, but it works – moving the screw one flat at a time.
- Leave the easy to get to screw in the mode door actuator in place until after the difficult one is removed. Once the difficult screw is removed, use a long screwdriver to hold the white cam plate back while the easy screw is removed and the actuator is pulled off. Failure to do so will allow the cam to move and need to be reset. There is also a hole in the cam cover that may be used to keep the cam from moving toward the driver side. I have not tried this yet.
As explained in the Jun 1 2025 GnarleyZ51 posting, I made the same mistake and the white cam plate moved towards the driver’s side, and the vent levers came out of the back side. I did have it held back with a screwdriver, but I must have bumped it afterward and it moved and the cam levers came out. Ugh. But not the end of the world -and not a requirement to pull the dash out!
What to do if you have lost the door cam locations. The white cam plate has come loose.
The black cam cover plate is attached by three 5.5 mm screws. One is very easy to get to. This is the last one to remove. Remove the upper screw using a 5.5 mm deep socket. The other two can be removed using a regular socket.
Assembling the two vent arms and the cam.
The upper vent lever arm has to be pushed to the highest position away from the cam axle. It will stay there if not bumped. The lower arm has a “spring to rest” position. Rotate the white cam plate where the upper arm goes into the groove which looks like the inner groove in the cam plate. This is easiest if that inner groove is rotated to the top side so that the upper lever arm does not go in the wrong slot. Fit it in place catching the center hole and then the lower arm into the outer groove. Hold it in place vertically. (Photo below is for reference as it was taken by Gnarley Z51 with the dash removed). This photo from Gnarley Z51 saved my bacon as I was not sure how the cam was installed until I saw this.
Test for operation before proceeding with full cam rotations in each direction. When you rotate the cam in the clockwise direction, you will notice that it will stop and make a gentle rest location at the end of its travel. This will hold the cam if you are careful while installing the cam cover. Notice that there is a bump in the end of this CW (clockwise) cam travel.
- Note that the black cam cover has a hole on the bottom side for the wiring harness.
- When installing this cover, install the easiest to get to screw first to hold things in place while reinstalling the other 2 screws. I pushed the screw thru a square of green masking tape to hold the screw to the socket until it was started. This is the cover reinstalled with the cam at the full Clockwise stop.
The new mode door actuator (part # 23201659) arrived with the setting on the 0 location. Using a 9 volt transistor battery on the 2 outer pins, if I put red + on the single end pin and black- on the other end pin in the opening, it would spin CW. Reversing and using black- on the single pin, and red + on the end pin, and it spins CCW. There is an arrow on the rotator pin, and an arrow on the actuator face. I rotated the missing tooth spot and arrow to the “260” arrow position. Be precise with this. I used small wires with alligator clips on the ends, and a paperclip in one alligator clip to touch the end contact that was near the other contact pins.
This allowed me to install the mode actuator. I set the top hole of the actuator on the pin first, then pushed the actuator in place. I installed the easy screw to hold it. A note about the hard screw. There are 2 holes next to each other. When I first installed the screw, I put it in the goofy star shaped hole by mistake. It took me a while to pull it out and start again. I suggest cutting off or plugging the star shaped hole. This is the hardest screw. I could not use a rachet and had to use a small ¼” breaker bar and tighten it 1 socket flat at a time.
I put the electrical connection on afterward as I felt dealing with the actuator by itself was enough work.
Hard part done! The rest of the job is putting it back together.
Next, I installed the lower blend actuator and then the terminal block. Then I installed the footwell plastic.
Calibration. (I’m not sure if this is necessary, but this is what I did.)
- removed fuse #17 (HVAC control) from the under hood fuse panel.
- rolled down both windows.
- disconnected the battery negative terminal in the trunk
- attached a wire from batt+ to this negative wire for 30 seconds.
- reinstalled the #17 fuse. (default for the AC is to be off)
I have a manual transmission, so I put the car in the run position (foot off the clutch and pushed start)
Wait 15 seconds.
- I Pushed the start button again to shut the car off. I opened the door, then closed it
- Wait 15 seconds
- Repeat this start and wait, stop and wait 3 times with 15 seconds between each.
- I opened the garage door, started the car, pulled out, pushed “Auto” with AC at 74.
- Air was now coming out the vents !!!! like it should. Yeah
- Put each window all the way up and then all the way down to recalibrate them.
I did test the old mode actuator. It functioned turning CW or CCW. I swapped + and - on the 9 volt to the end wire connectors. This actuator sounded different in each direction. The new one sounded the same no matter which way it turned. AC was stuck on Defrost and floor, so something was wrong with it and now I have my vent setting back. It is a good day.
Still a 1 day job and would have gone faster had I known how to do this. No special tools required but it is quite time consuming. If I had to do it over again, I would use something like a lag bolt or a peg with a head to go into the wiring harness hole in the cam cover. Put some tape around it so it fits snugly and will not allow the cam to move towards the drivers side. A lot more work if you lose the cam. Shame on Chevrolet for making it this way, but something we have to deal with. Hugh
Last edited by Hughsray; Sep 17, 2025 at 01:45 AM.
