rockblock

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

PwrDriftr

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.

rockblock

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

PwrDriftr

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