[T3] Aux. Air Reg. Rebuilds

Jim Adney jadney at vwtype3.org
Sun Jan 29 16:29:09 PST 2012

This afternoon I was trying to clean up my workbench, when I came 
across some AARs that I'd been trying to revive long ago. The problem 
with these is that the zinc die castings seem to have a tendency to 
warp over time and that causes the shaft & valve inside to bind. I 
had been wondering how I could machine those parts to work together 

Looking at those parts again, it struck me that I could use the same 
technique that I use to lap the bore of the pressure relief valve on 
the FI fuel pumps. The AAR bore is much larger, so I had to make a 
different lap.

I tried it and it worked. That AAR is now smooth as baby poop. The 
difference is really dramatic.

For those of you with FI, this is the AAR that was used on all '68-9 
FI Type 3s and on all '70-3 MT/FI Type 3s. This is NOT the 
electrically heated AAR that was used on '70-3 AT/FI Type 3s.

This shaft should turn completely smoothly, with no interference at 
all. That way, the idle speed can respond smoothly as the engine 
warms up. It doesn't take much interference to keep that bimetal 
spring from moving that shaft. If you have your AAR off of the 
engine, it's easy to check this: Just stick a screwdriver in the slot 
at the bottom of the shaft and see if it turns easily. It will run 
into stops at its two extremes, but it should be completely smooth in 

How many of you are having trouble with this AAR? My guess is that 
it's more common than most people know. Once I get a little more 
experience with the job, I'll settle on a price for the rebuild, but 
it should be fairly cheap.  

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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