Regen issue?

relumalutan

Veteran Member
Joined
Dec 6, 2012
Location
Michigan
TDI
2011 Audi A3 TDI, 2006 VW Jetta (Sold)
I'm new to the CBEA platform, coming from a 2006 MK5 Jetta TDI.

Bought a 2011 A3 with 129k miles 6 days ago. I scanned it with VCDS, no errors. Everything was fine for the first 2 days, on the third evening after a 20 minutes 15 miles uneventful drive from work in 70 degrees weather with no AC on I noticed the fans kept running after I turned the engine off. It appeared the exhaust was hot, so I thought to myself: this must be the mythical DPF regen. that I heard of. So I turned the engine back on and let it idle for a while. This time the fans turned off when I turned off the engine after 5 minutes.

Same thing happened again the following two evenings. It does not happen during the day, no matter how long I drive the car. It always happens at night after my 20 minutes drive from work. Did some research, came around this posting: https://www.audiworld.com/forums/a6-c7-platform-discussion-194/cooling-fan-staying-2860392/
It appears there are two opinions:
1. The fans running to cool of the turbo. It does not make much sense to me, why the fans don't run during the day after driving a long distance?
2. The thermostat being bad, and not being able to maintain a high enough engine temperature for the regen. to successfully complete. The thermostat needle on the gauge usually sits slightly below the center.

What you guys think might be the issue? I thought the regen should occur on average once a month or 700 miles.
 
Last edited:

TurboABA

Top Post Dawg
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline '14 A6 Technik S-line
The issue is you don't know how to use VCDS.
Post full scan, then post your DPF stats and regens stats.
 

pedroYUL

Top Post Dawg
Joined
Sep 8, 2011
Location
MI, USA
TDI
2015 Passat CVCA; 2015 GSW CRUA; 2004 wagon BEW(brother)
To me, it sounds like you interrupted a regen, then the car tries again to complete it, and maybe you interrupted it again?
 

relumalutan

Veteran Member
Joined
Dec 6, 2012
Location
Michigan
TDI
2011 Audi A3 TDI, 2006 VW Jetta (Sold)
It was the thermostat, I assume it was stuck open. The coolant never reached operating temperature (90C), it only reached 70C. I monitored the coolant temperature with VCDS while driving. Based on my research and input from another forum member, if the coolant does not reach 87C, the ECU is preventing the regen from happening. I was planning to replace the thermostat myself, but the job appears to be a PITA. Got a really reasonable quote for the job from a reputable repair shop, they will replace it next week.
 

relumalutan

Veteran Member
Joined
Dec 6, 2012
Location
Michigan
TDI
2011 Audi A3 TDI, 2006 VW Jetta (Sold)
Final update: replaced the thermostat and the coolant pipe (along with the the oil cooler gasket). The coolant now reaches the operating temperature, regens are back to taking place, and MPGs improved.
 
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