: No A/C Cooling Passenger Side Front Dash Vent

06-24-12, 09:41 PM
Hi, hope you can help.

2006 STS AWD 4.8


Recently I lost cold air supply on the passenger side front vent.

1. The temp display and control appears to function normally.

2. I have heat control out of the same passenger front vent.

3. The driver side HVAC is normal.

3a. Both front seat electronic heat/cooling is dead, but the fan sounds normal.

3b. Rear seat electric heaters has never functioned. When I toggle the button once, the LED illuminates briefly and then won't illuminate until I cycle the ignition.

4. I removed the glove box and bottom plate above passengers feet to gain access the A/C unit in the center dash. The Lower Right Vent Actuator (LRVA) moves with changes in set temperatures. When requenting max cold, the Passenger Arm Vent Arm (PAVA) attached to the LRVA moves down and towards the back of the vehicle. Which I'm assuming is normal.

5. After removing the LRVA and move the PAVA though it's full range of movement, I cannot get any cooler air than what the LRVA was doing. I can get the heat. It always feels like the ambient air temp and no colder.

6. The Upper Right Vent Actuator (URVA) appears to be normal.

I've found 3D drawings of the A/C unit, but I can't figure out what to check next. Where's all the cold air? What am I missing?


06-25-12, 12:02 AM
The first thing you really need to do is have someone with a Tech2 scan for codes. This should always be your starting point and may offer some valuable information. This is a system not easily "user serviced", primarily because of the diagnostic tools required to determine what the problem is.

As for the heated/ventilated seats, both front and rear, is it safe to assume you've checked all fuses? The symptoms you describe in the rear are often a faulty element. I'm not convinced of this unless both sides have seen a lot of use.

06-25-12, 11:07 AM
Try this. You are low on Freon 134a, charge it to specs and you should be GOOD to go.
Your other problems are probably NOT related to this.
Good Luck.

06-25-12, 11:48 AM
Hey Subsailor613, are you saying there are two separate evap coils in the HVAC Unit?

06-26-12, 01:02 AM
Try this. You are low on Freon 134a, charge it to specs and you should be GOOD to go.
Your other problems are probably NOT related to this.
Good Luck.
I agree that the vent problem is not likely associated with the heated/ventilated seat problem. Having said this, if the A/C works from all vents except the passenger side dash vent(s), your position that the vehicle is undercharged doesn't make sense. This really sounds more like some type of HVAC actuator problem. Code retrieval and performing some of the diagnostic testing will be much more effective in tracking down the problem.

As for two separate evaporators, no, there is not.

06-28-12, 02:25 AM
My car did the exact same thing. It was low on 134a.

06-28-12, 11:44 AM
Thank you kschwed, for your post.
Whether it makes sense or NOT, it works, and fixes the problem !
My Car did the exact same thing.It was low on 134a.
This is a HELP forum, not a personal forum. SO HELP those who need it.
A can of R134 only costs $ 20.00, and the adapter costs $ 20.00,@ AutoZone.
This is less than $ 100.00 and worth a try.
You probably NEED the adapter, with a guage anyway, as you may have a
slow leak, test your system, and go from there.
Good Luck !

06-28-12, 12:18 PM
Subsailor613, I really appreciate your advice. I plan to add freon like you advised. We all know that some fixes to electro-mechanical stuff doesn't make sense some times. And if it fixed other yours and other STSs then that's all we need.

I wish I could pull the HVAC out of my dash and analysis the actual mode of failure but it's not worth it.

Again, thanks everyone for your input.

06-28-12, 08:46 PM
My driver vents were very cold and all other vents, even the back seat, were not cold at all. I recharged the system and it has been great ever since.

06-28-12, 09:10 PM
I was going to to start a thread on a similar problem I'm having but now I'm thinking it's all the same...my driver side vents do not go up and down when I change the temp(they stay around 75)...the rear vents do go up and down when temp is changed...passenger side works fine....any thoughts?

06-29-12, 02:41 AM
Every time I chime in to HELP someone ddalder chimes in and puts out bum dope.
This is a HELP forum, not a personal forum. SO HELP those who need it.
Bum dope? You are certainly entitled to your opinion. Whether your solution works or not, what did I advise the OP that wasn't reasonable and of a helpful nature? I'm pretty sure I recommended a more industry accepted approach to troubleshooting the problem. You simply elected to throw out a potentially costly solution to something that may or may not be the same issue, without following logical diagnostic process. Perhaps if you didn't have such a half-baked approach to most things, I wouldn't continue to discount the value of your posts.

Shall we review some of your history?

06-29-12, 11:23 PM

While the surface symptoms may not ordinarily lead one to the offered solution, the real world often produces odd cause/effect/solution linkages. In marginal conditions, one edge of a heat exchanger might be expected to be less efficient. A Tech II would likely verify this as well.

Sometimes Occam's razor nicks the chin.

06-30-12, 08:14 AM
Yes, Perhaps i jumped the gun on this one, I withdraw "bum dope"
Happy Miles.

07-11-12, 02:37 PM

1. The air temp on drivers side front vent measures 58F or 14c, which is better than normal A/C performance forthis system.
2. The air temp from passengers side is the same as interior temp. Temp control appears to work, but no cold air available.
2a. If I increase the set point on the drivers side, there is still no cooling available for the passenger side.
3. I bought the Service Manual (3 Volumes $300). There is no mention of this mode of failure.
3a. I have correctly identified the passenger vent actuator and vent lever and I removed the actuator and opened the vent fully...no change.
4. I will wait until next spring for the leak test and refill.
5. I understand the concept of a thermo gradient across the surface of the Evap, but it's seems to great to me.