[T3] 73 auto trans type 3 ARR ?

[William Jahn]

 I checked the AAR today and drove the car. The AAR was open cold 76
Degrees here. After I blew in the hose to see if it was open, engine off.
Then I drove it today the RPM never increased and actually dropped down to
800 RPM in drive. Once I got home I checked it and it was closed. I didn't
feel any suction at all however the idle was back up to 1400 RPM.

 I now know it's not the AAR , Since it does at times drop to 800 RPM in
drive at least today it did, Then with the AAR closed and I did not adjust
the Idle speed because when this rpm rises I have 1000 RPM in drive. All I
can think of is some new vacuum leak and I didn't see any hoses off and
just changed them all last year along with everything else intake gaskets,
Rummer boots , injector seals, fuel lines, every single hose.

 All I can think of is a new vacuum leak or the dist sticking maybe a
broken spring  but it does not ping one bit. It does run fine.  I hoped it
would be simple , guess not.

William

On Fri, Jun 9, 2023 at 12:15 PM Jim Adney <jadney at vwtype3.org> wrote:

> A few more comments on our AARs.
>
> There were two different versions: a mechanical one for '68-9 Type 3s as
> well as all later MT Type 3s, and an electrically heated one for '70-3 AT
> Type 3s. To the best of my knowledge, VW/Bosch introduced the electrically
> heated one to heat up faster to meet emission specs for AT cars.
>
> The mechanical AAR has a bimetal spring, just like the one you used to
> have
> in your home thermostat. That bimetal spring sticks down into the engine
> case and gets splashed with engine oil, so it heats up with the engine.
> The
> bimetal springs do not wear out, but the housing is a zinc diecasting,
> which
> can distort with time, causing the shaft to stick. This is particularly
> likely if
> someone overtightens the two screws on the top. This pulls on the zinc in
> a
> way that will distort the housing and cause the AAR to stick in place.
>
> I can lap the housing bore and reset the spring to open and close
> properly.
> It's not a hard job, but I had to make some special fixtures to do it
> easily and
> correctly. I Locktite the screws, so they don't have to be tight.
>
> The electrical AAR is a crimped assembly, so it can't be taken apart
> without
> cutting and bending things. It pretty much amounts to something you CAN
> take apart, but it's not likely to go back together nicely afterwards.
> I've never
> done it. They also stick, but I'm not sure why. Sometimes they can be
> freed
> up by cleaning with some sort of solvent, but often this doesn't work. The
> only way to fix them is to replace with a working one.
>
> Replacing an electrical AAR with a mechanical one should be fine. It might
> not heat up as fast, but this is unlikely to be noticable unless you're
> driving in
> extremely cold weather (think freezing or less.) Being able to fix the
> mechanical ones is a huge advantage.
>
> There's one possible problem with this replacement: I've been told that
> some
> late AT cases do not have that hole drilled out, to let the MT bimetal
> spring
> AAR stick down into the case. I've never seen this, but I've heard others
> make this claim. If anyone comes across an AT case that does not have that
> drilling (the one for a carb type fuel pump pushrod) please take a picture
> and
> let me know.
>
> Testing:
>
> The ONLY reliable way to test whether your AAR is open or closed is to
> block off its air inlet with your thumb, with the engine running at idle.
> If the
> idle speed drops, the AAR is at least partly open. If the idle doesn't
> change,
> the AAR is closed.
>
> It's important to understand that closed does not mean a complete shutoff
> of
> air. It's not a fully sealing valve. Some air will always pass thru, but
> if the
> valve is in its closed position, there will be too little air to alter the
> idle speed.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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