[T3] 73 square auto trans aux air regulator?

[William Jahn]

 Part of the problem is most of the time I don't drive very far , just
short trips nearby , the engine does not get close to fully hot. I know it
is open on startup and it does fully close when I test it. It seems even a
10 minute drive even at temps in the 60's it should close. I do know when
the weather is warmer it closes much faster. Even then on any cold start
regardless of ambient temp the RPM is say 900 RPM then the time it takes
around 10 minutes to back out of the garage then the RPM is 1400. Even
after a short drive as described above and it sits for an hour while in a
store I start it the RPM is normal then climbs back up. I do know if I
drive farther it does close. If I'm fast enough I place it in drive before
the RPM climbs. I think just the cool ambient air flowing through the valve
in some way pulls any heat the valve's coil builds up when all is trying to
heat up. Inside the valve the element is heating a small chamber but the
metal parts of the valve are like a heat sink. Does not explain why it used
to work better..I know after I rebuilt the AT AAR I powered it up and
watched the valve close and it took maybe 10 minutes and moved slowly but
smoothly. This last time I didn't remove it to see , you can't see just
removing the hose with a mirror. I just know it did close without jarring
it. Even when I drive a short trip for 10 minutes and place it in park the
RPM is at least 1200 RPM when I shut it down.

 When I got this car upon start up the RPM never varied much , it was
slightly above 900 RPM in park and dropped to 850 , it never stood out
like  now

 Also I have the 73 case sitting here , it does have a hole in the case, I
didn't measure it but it looks to be more than an inch. I rebuilt a 72
case, I had been sitting as a spare and don't remember if it's the same. I
know I used the old bracket for the 73 case. I thought all cases have this
hole for the mech fuel pump.

On Sun, Jan 29, 2023 at 8:11 AM Jim Adney <jadney at vwtype3.org> wrote:

> 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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