T Feeney

I have a 2016 Q5 with 88,000 miles. Noticed the fan running after use, which was new. Next day the fan cycled on for about 20 seconds and the car had been sitting all night.
Mechanic found a defective wire (relay). Replaced wire fixed the issue.

beckycvo

My cooling fans run more than normal after the vehicle is shut off. They will even come on if it’s been sitting and I open the door. No warning lights are on. Car runs fine. Air is cold and temps run normal. I took to dealership and they said I need two cooling fans and a relay. Total repair is $5200. I brought the car home. Now what??

HippoAudi

My car (2011 Audi A8) is doing exactly the same thing. Fans run all the time while the engine is running and for several minutes after shut-off. Fans will even come on for a few seconds when a door is opened, etc. with the engine off. Your dealer's comment that you need new fans doesn't make any sense since the fans are running strongly. It is most likely a problem somewhere in the control mechanism - a relay or sensor or control module. The fact that they go on briefly when a door is opened should provide some sort of clue. Seems like any electrical activity in the car triggers the fans. Has anyone out there resolved a similar problem?

dbbyleo

If you have a diesel… read on:

When this happens, it means your car was in the middle of DPF regen when you shut the car off. There’s excessive heat that need to dissipate during a regen. So that also means you interrupted a regen.

Having said that… if this happens frequently… say even once a month… there one of a couple things that could be happening:

1. You have a terribly short commutes. TDIs hate short commutes because DPF regens need longer drive time to complete. This could be why you have frequent regens… or why you seems to always interrupt a regen. This is why I thought I was having this symptoms… and didn’t think anything of it. But then finally… the DPF warning light came on.

2. You have normal commutes (you regularly drive 30min or more), but this symptom persist. If so, this could mean your thermostat is dying. And the regen that’s not completing is actually your NOx storage regen (not DPF). I realized this was my issue. Your DPF light will eventually come on and the fault code of P1A58 (NOx regen required) will be present. Here’s a TSB that directly address that:

https://static.nhtsa.gov/odi/tsbs/20...69515-0001.pdf

the first step in resolving this issue is to check the thermostat. If you have a VCDS, you can do it yourself. I do, and I found my thermostat was not maintaining my engine temp high enough. Regens apparently need engine temps to be at a certain level (makes sense). Not having a VCDS, the tell tell us also your temp needle gauge. My needle can barely stay on center. And when I’m at a stop light, it drops slightly below center.

i was lucky… when I finally took my car into Audi for the P1A58 and DPF warning light… they did not cite the thermostat as the root cause. Instead they replaced my NOx (under the diesel gate warranty). The thermostat is not covered by that warranty. But the NOx is way more expensive than the thermostat so I was happy they did the NOx and (seemingly) overlooked the thermostat.

But from what I can tell in my research… a bad thermostat will cause your regen not to complete even if you’re not interrupting it (since engine temps isn’t high enough)… and eventually ruin your NOx storage. As soon as they replaced my NOx for free… I told them to go ahead and replace my thermostat (cost me $950). Replacing the thermostat on these TDIs is a pain.