AAR auxiliary air regulator (valve)

[alfa4door]

AAR auxiliary air valve



what you see above is the AAR, this device sits on the number 5 intake runner. Its function is to allow extra air into the engine when the engine is cold. It is heated to operating temperature by a 17 Oms resistance (@ 12 Volts that is about 7 Watts power) that bring it up to operating condition in only a few minutes from start up. At operating temperature no extra air is allowed thought the system as a bimetailllic strip bends to the heat of the electrical resistance thus allowing a spring to shut the trap door that admitted air when the device was cold.

The normal failure mode is open, most often when the electrical resistance fails and does not supply heat to allow the bimetallic metal strip to bend out of the way of the trap door while it is trying to close. there can be mechanical failure in the fisical mechanism, the spring that closes the trap door can fail. If it fails in the closed position the car may be hard to start and would not keep idle when cold.

All this to say that in my case the AAR was not closing compleating resulting in a high idle when hot, 1700 to 2000 idle rpm.

It was not a failure of the heating element. I took the AAR out of the car and connected it to a spare battery. In about 180 seconds the trap door closed but I could still blow air thought the device.

It turned out that the problem was with the trap door pivot bushing itself. This trap door works like a guilliottine across the oval opening you see in the picture. A plate inside the device rotates under spring force to cover the opening when allowed by the rising temperature . This plate rotates about its center and rotates about an axle that is cold fitted to the device' casting. You can see the outer end of the tiny axle from the outside just above the "S" of Bosch. (red arrow).

My problem which I suspect is more common than previously thought, was that the plate and its axle had moved away from the seat in the casting and even when the trap door was closed air was allowed to leak between the plate and the body of the device itself, In other words the trap door was standing away from the casting, too much play.

The solution is to drill out the rivets at all 4 corners, (blue arrow) open the device up and reset the trap door and its axle back further into the casting, taking up the play in the pivot thus denying further air leaks. it worked great.

By then I had already bought a new one but I thought you may may want to avoid my error and fix yours before you go out and spend yet an other 300 $.

Andrea

[Scott R]

It's also very adjustable, I've added about 5 mins of warmup to my engine.

[timmy2]

Thanks for the post.
I just fixed my spare that I have made adjustable for time closing but still leaked air.
A few taps with a hammer to get it where it needed to be and it's closing off all air as it should now.
Might even swap it with the one in my car now.