A4 B7: Fan Stays On After Engine Cleaning

Hello, after washing the engine, the fan no longer turns off. I opened the fan control unit, and everything is dry. I'm wondering what could have happened after the engine wash that would cause the fan to not turn off, even when the ignition key is removed. The fan only turns off when the engine is running or the ignition is on; if you remove the key, the fan turns on after 15 seconds. It's strange, and there are no errors in VCDS .

Hello,

I would first check the coolant temperature displayed in the engine control unit and the instrument cluster, as shown in the measured values.

Best regards, Rainer.

ascendens wrote:

Hello, after washing the engine, the fan no longer turns off.

Deshalb bläst man auch nicht mit dem HDR in den Motorraum. Just a side note.

Otherwise, all that remains is to check the electrical connections and maintain them with contact cleaner or WD-40. Secondly, I would recommend parking the car in a warm environment to speed up the drying process.

Perhaps you should remove the fan control unit and let it dry out completely.

Thank you to everyone, I will proceed exactly like that, and I will make sure to dry everything thoroughly.

I followed all the good advice.
Checked the engine temperature with VCDS, everything is okay.
Opened the fan control unit, disconnected the fan connector, detached the compressor connector, and let everything dry.
Everything is back together and working properly again.

I don't know exactly what caused it, as I couldn't see any visible moisture.

Thank you very much for your help .

That makes me happy!

I hope it stays that way and that there are no late consequences, such as corrosion.

Thank you, but the long-term effects have already occurred. One day it was fine, then started again, but the symptoms have changed. So, if I turn off the engine, the fan might stay off, but sometimes the EGR valve rattles when I turn off the engine, for about 30 seconds, and then the fan starts running. This morning, for example, I turned off the engine, and then the fan tried to start, as if it wanted to, but it couldn't. It tried a few times, then it stopped.

I still disconnected the battery so that the car won't start and drain the battery.

Everything is very strange, what do you think about that? VCDS still doesn't show any error codes.

There's no other way than to open and dry each connector one by one.
hg
Herbert.

Herbert wrote:

It will be necessary to open and dry each connector, one after the other. hg Herbert

And spray it directly with contact cleaner, WD40, or a similar product.

Hello!

It might not be entirely accurate for this particular car.
"But I once had an Audi, and the fan would sometimes turn on by itself."
The cables from the fan motor to the radiator frame were strangely routed, twisted, and under tension.
Over the years, the insulation has deteriorated, and there have been occasional short circuits between the individual wires.

I think it was an A3, but I don't remember exactly.
You could take a look at it.

Thank you for your responses, but I think the issue might be resolved now; the electrical components should be dry, but the fan is no longer working.

"Does anyone know where the comfort control unit is located? After the short circuit I caused, VCDS shows that the functions of the devices are working intermittently. Sometimes the central locking works, then I get an error message about the brake light, even though it's working, and so on."

I was thinking about exchanging it. What do you think about that?

It should be located directly in front of the driver's seat, under the carpet, in a black plastic box.

Quote:

Everything is very strange, what do you think about it? VCDS still doesn't show any errors.

So, what now?
What short circuit occurred back then?
hg
Herbert.

Great post. It would probably be better to tell the whole story from the beginning, so that hopefully no one would respond. Because if you already have damage and malfunctions in the vehicle due to modifications, those should be fixed first. Then, searching and measuring will be the key to success.

Okay, you're right! So, I completely overhauled the engine some time ago, and now all the related components are new too. It currently has 480 km on it. The problem was that, during the reassembly, I accidentally forgot to disconnect the battery, which I had reconnected because of the radio. And then, when I was installing the starter, I accidentally touched the wrong cable to ground, and it sparked and made a loud noise. Since then, the central locking system has only been working intermittently, and the steering angle sensor is showing an error.
When I apply the brakes, it sometimes displays "rear brake light defective," even though everything is working. My thought was to check all the cable connections that lead to the comfort control unit to see if any are carbonized, oxidized, or even burned through.

Perhaps someone can recommend a more effective approach.