Folks,

I have a 1999 A4/2.8 Quattro...yesterday, I noticed a weird "fan" type of noise coming from the right side, near the radiator, just below the air duct (none of the 2 big radiator fans). After I shut down the engine...after 4-5 minutes, the noise dissappeared, but after another 4-5 mins it came back on...I'm not sure where or what exactly generates that, but I hear it and I can feel a draft right next to radiator. What's weird is that it goes on & off every 5 mins, even with my engine off...last night it drained my battery and I had to recharge...the only way to stop this on/of noise is to disconnect the battery...

After I charged the battery, I ran ODB2 diagnostics and no fault code came up. When I ran VAGCOM, I got the following fault code:

Address 01: Engine
1 Fault Found:
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-10 - - - Intermittent
Readiness: 0000 0101

After a reset, no further codes appeared, yet the fan keeps going on/off every 5 mins...any clues what it could be?

Thx

 

This may help. My business partner had the same problem (2 years ago), in his BMW 540i. Since both cars are German, maybe I can provide some insight. Every night he'd park his car and in the morning the damn battery would be dead. After months of frustration (and a completely stumped BMW mechanic) we found the problem.

It was a faulty fan relay switch (final stage resistor in BMW speak). The relay was triggering the fan and the fan would just blow all night until the battery died. It was a $200 part and the relay was mounted up behind the glove box. Since both Audi and BMW are luxury German cars, I wonder if your Audi is having this same issue.

 

Thx PwrDrift, you're right..."A4Cragman" from another forum provided me with this solution:

"What you are hearing is the secondary air pump. Its function is cold start emission control. The fact that its not throwing a code means its doing its job when you start the engine. The problem with it coming on and off like it is is most likely a sticking relay. The fix has two options, the first of which is free. The relay is located in the ecu box on the driver's side behind the second firewall; big, black, plastic box, can't miss it. Open that up and you'll see the ecu and a small, gray cube that is the relay. Unplug the relay, give it a shake and plug it back in and put everything back together. If you do it with the battery disconnected, plug the battery back in and go drive for 50-70 miles to get all the readiness codes enabled again and see if that has fixed the problem. "

I took the relay out, gave it a few taps & shakes and now the Secondary Air Injection pump (AIR) seems to have stopped turning on & off

 

Sweet (pat myself on the back), good luck with the fix. I hope it works out!