[T3] 73 square auto trans aux air regulator?

Jim Adney jadney at vwtype3.org
Sun Jan 29 08:11:11 PST 2023

On 28 Jan 2023 at 12:40, William Jahn wrote:

> I took mine apart a few years ago because it was stuck. It works , however
> in colder temps say 45 degrees when I start the car the rpm is 850 RPM a
> few minutes later just backing out of the garage the RPM is 1400 RPM and it
> takes a while before it drops back down or closes.

When you shut the engine down when hot, the AAR will be closed, and if it's 
a bit sticky and there's no engine vibration to shake it back to its equilibrium 
position, it will stick in the closed position. The next time you start, it will still 
be closed, but the bimetal coil is cold and wants to push the valve open. 
Before long, engine vibration allows that to happen.  

>  I removed the connector , you have to because if you just apply 12 volts
> to the red wire in that connector it powers up the fuel pump. I did this to
> check if it was first open and how long it took to close . It does close
> but takes longer than what the specs call for. When I had it open to clean
> and repair I even set the clock spring so it would have more tension. I
> would say with 12 volts it takes well over a minute to close.

It's misleading to view this as a spring. It's a bimetal positioner, which will 
only have tension on it if the valve is stuck or if the positioner is pushing the 
valve against one of its end stops. If you move the positioner, you've 
changed the calibration, which will change the time and temp that the valve 
will close.

>  I don't feel taking it apart again which is a pain will help. I thought of
> finding a way to just add a toggle switch to the red wire so it can  heat
> it so it closes.

I don't blame you for not wanting to take an AT AAR apart. I've never done it, 
because it looks like I'd never be able to get it back together nicely. You 
pretty much have to destroy it to get it apart.

I don't see any point in adding a toggle switch to its circuit. The fuel pump 
relay powers it even before the engine starts, so adding a switch either 
delays the AAR warmup, or it requires you to power the AAR before you try 
to start, meaning you have to sit for a few seconds: something most of us 
wouldn't do.

> I also have a mechanical one that I got from Tram on Samba that he cleaned
> and rebuilt and found the proper arm for the throttle return spring since the
> one on the electric unit is part of the unit's base. From what I recall these
> rely on oil temp and may take even longer to close. 

I like the mechanical ones. They have their own problems, but at least they 
can be taken apart and fixed. I've been told that some late AT cases don't 
have the hole for the mechanical bimetal spring to stick down into the case. 
I've never seen this, but I've never removed the AAR stand from my '73 AT 
case. YMMV.  

>  The main thing is I don't like placing the trans in gear at 1400 RPM. Or
> if that's even a concern.

It's good that you've thought about this, but I don't think it's really a problem.

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

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