I suspect there is an issue with the HVAC on my 2015 Q7. For my 2016 Touareg and 2015 Passat, on a hot day, when I get in a hot car, I get full blast fan for awhile and then it falls back after a few minutes. In Q7, I get maybe 1/2 to 3/4 fan. If I adjust the HVAC controls manually, everything seems to work. I can get full blast fan, and the air blows from the correct vents when I select the different vent positions. I don't have any codes in VCDS. I got Q7 used, and the HVAC has been that way since I got it. If a crank the temperature down in AUTO mode, the fan does start to pick up speed, but I have to be within a couple of degrees of minimum before it will start approaching full speed.

My suspicion is that there might be a climate sensor that isn't working...not badly enough to throw a code, but reading wrong. Maybe indoor temp, outdoor temp, sunlight (I don't know what sensors there are). I inquired on the Ross-Tech forums some time ago if anybody knew codes for monitoring the HVAC sensors, but got no reply. The outdoor temperature that reads on the center display is correct.

Does anybody know what HVAC sensors the Q7 has for controlling the indoor temperature, and if there is any way to monitor what those sensors are actually reading with VCDS? Any other thoughts?

Thanks!

 

I have no solution for you but my fan would run 1/2 speed, 3/4 and all over the map and at some points not spin at all. Replacing the fan was a 10 minute job and cost maybe 70.00 Canadian for a fan from Amazon. I think the bearings in the original fan were getting old and probably dust, hair and bits of crap in there were taxing it to death.

 

Thanks for the reply! About a year ago the fan on the passenger side started squeaking a little bit. I took it out, cleaned it, and relubricated it. The fans run fine when the set to full speed manually.

 

The Q7 uses sensors at the windshield inside car to detect the passive heat, and of course, there's a temp / humidity sensor, etc. I think that one is right behind the HVAC panel in the dash...there's the vent in the plastic fascia right in front of the shifter, etc.

I haven't tried to monitor the HVAC interior temp sensors prior, so I'll have to go hook-up VCDS to see what is available to monitor. I have been in the HVAC prior, but just to look and verify what temps it was achieving/measuring internally, so focused on the freon charge and compressor performance, etc.

The blower speed is actually controlled by the variable resistor module (mounted just to the left of the blower fan), which I assume gets signalling from the HVAC head unit based on the myriad sensors feedback loops.

What I know for sure, is when my pano-roof sunshade is closed, my fan doesn't blow full-out either, but I've also added ceramic tint to inside of the windshield, which reduces the sensor feedback. Still, if I drop the temp control a few degrees, the fan speed jumps which each temp change I make, etc. Typically I leave it in AUTO mode.

The most important thing I've found related to poor A/C performance is inside the MMI controls, settings for the A/C there's a setting for auto-recirculate, and you need to be 100% certain that is turned ON. I believe it defaults to off when the battery is disconnected, etc., as I've had to switch it back on after a battery swap, or getting my car back from a long, long stay at the Audi dealer when it was under warranty, etc.

When the recirculate auto-engages, that makes it feel as though the fan speed has increased, but it's really just in bypass mode pulling air from the interior only, and this reduces the humidity...making a huge difference in comfort. You can also listen for this switchover to recirc or simply test it yourself manually by hitting the manual Recirculate button, etc.