I have a 1999 Audi A4 2.8 30V and when I start it cold, or after not using it for about an hour, my electric fan kicks in full speed and sounds like a jet taking off. It also effects the way the car shifts and it'll go up to around 3100 RPM before it kicks over unless I tip shift it myself. It lasts a total of like 45 seconds to a minute and when the fan stops doing its thing the car shifts normal again. I'm posting here and on reddit just looking for some help because this has stumped me.
Its not throwing codes for the fan contol module, or anything else really. I get readings because I did a cat delete but that's it. And if I unplug the MAF it stops doing it, I just put a new MAF on it last week so I don't think thats the issue unless I got super unlucky. I dont know where the fan control module is located, and the previous owner took the plastic skid plate off and never put it back on so a lot of stuff on the bottom end is all gunked up.

 

Are your coolant temps fine? The coolant temp sensor is a part that regularly goes bad and that going bad (if it did) could be related to your fan going nuts.

 

Replaced the CTS about a month ago, it was indeed bad but my temps don't get high at all.
I was having issues with the engine running rich so I've done a lot to try and pin the issue, MAF, CTS, Cat delete, New O2 Sensors with anti foulers.
And yesterday after cleaning my throttle body my flywheel chewed up my ESS(Engine Speed Sensor) VAG pulls it up as G28 and the car wont start at all. I'm not sure if something got inbetween the bell housing and the engine, but I've never seen anything like it. The end of the sensor is chewed halfway off on one side.

 

When I replaced mine I didn't put a spacer in (not sure if there was one on the old one and I didn't see it or what) and it chewed up mine a bit too. Still worked but I ended up replacing it again and just not tightening it down completely. It's still secured in there but probably not torqued as much as it could be.

I was also doing some work on my throttle body and I dropped a hex bit between into the bell housing. There's a small vent hole just under the throttle body into the top of the housing - that's where it went. It ended up shearing the rear main seal which had to be replaced. It had to be towed to the shop because it wedged itself in the flywheel. Those + a new clutch cost be $2200+

In any event, I don't really have an answer to your original question. Fan control module like you said.. see if you can find a used one to put on temporarily.

 

Thanks for the info
Yeah I deduced that the plastic had already broken on the CPS and when I was messing with the throttle body I pulled on the wire enough to move it out of position and that cause it to get chewed to death.