gag4o

The AC and the heater on my D3 4.2 works some times only. When I start the car in the morning it works great - blower works and the ac blows super cold, also heating works with no problems on all modes (Auto or manual dual zone settings). When I turn off the car and start it later in 1 -2 hours the AC stops blowing (the heater too) and then in 10-20 minutes of driving starts back again. Sometimes doesnt stop blowing for days and then suddensly stops again.
The car is equipped with the solar sunroof which also either works when the AC do, either stops too.

When the AC stops blowing I turn it on and off a few times to check if the compressors kick - and it kick at all the time but as I said - sometimes no air blows out of the vents...

Is it some sort of sensor or resistor??
thanks

richard-tx

Sounds like Blower motor to me.

MP4.2+6.0

Search archives--not even very long. Sounds like you have the fully predictable and treatable solar roof syndrome. It has been coming up systematically on the board the last few years. Fix is straight forward--replace HVAC blower unit. If you want to tinker and take dollars out, replace the motor brushes. Both have been posted on, including various pics. The problem is the solar roof runs the fan any time the car is parked in sun. Increases the elapsed run time on fan many x, especially if you + prior owners don't park in a garage. Same fan though as the non solar 4.2's. Don't think Audi thought this through, and didn' all the way back to my 2000 A6 4.2 with a solar roof, where I first started running into the issue about 10 years ago.

Also, sort of as the longest term on this, this issue has shown up a time or two now on the D4 boards too. Well, also look carefully at a 2016 A8 if you configure it on the Audi USA site. Hmmm, no solar roof option. Disappeared from order guide also. I crossed it off my list anyway--both I like the view and the field experience reliability issue is now pretty easy to figure out.

richard-tx

On the plus side the Solar sunroof option makes a HUGE difference in the summer.

gag4o

OK, thanks for the advice. Before I posted the thread I read many other threads of that problem and specially MP4's comments but cant find the one with pictures.

SO I will look for a blower motor. First I figured that if it blows from time to time cannot be blower motor...I toughts its some sort of temperature sensor but as you are saying a new blower can solve my problem

Beleive it or not the solar sunroof is not a new option. The c5 A6 was not the firs Audi with it. It was available option in the early 1990s on the Coupe Quattro and on the b4.
Actually it was super common on the COupe QUattro ABT (which was super rare though)
thanks again

richard-tx

Intermittent operation is exactly what happens when the motor brushes wear out. It is so common that old timers will remember the temporary fix of hitting starter motors with a hammer when they start to fail. The shock jostles the brushes into making contact permitting one or two more starts.

Anyway, the blower motor will eventually stop working altogether.


My advice is to change the blower motor with a new one now, then take the original and replace the brushes and keep it on the shelf for the next time.

The commutator bars of the blower motor is fairly thin. Generally one brush change is all you can get from the motor. After that the commutator is just plain worn out and the motor is scrap.

gag4o

I apreciate your help.

MP4.2+6.0

Fan pic in this reply among others--near the end: https://www.audiworld.com/forums/a8-...ently-2885462/ You can see it is easy to access from under hood back in plenum area below HVAC filter. More here, including work in process from one of the long timers (Mister Bally) who did this job early on: https://www.audiworld.com/forums/a8-...motor-2840964/

Yes, I know the solar roof w/ fan has been around a long time. Along the way they also increased the cell count in the roofs to give it more juice/oomph. The point though was more that Art in Engineering isn't up to snuff. The fan design shortcoming on this thing has been quite obvious for a long time and costs owners secondary extra cash to fix/maintain, yet it soldiered on with same basic design that wears main blower fan.