Testing an Auxiliary Air Regulator in a 1979 super beetle

[kinggeorge13]

So yeah, two days into my nice new 3 month ICBC insurance for the summer and our little 1979 Super Beetle starts not running well at all when it's first started with a cold engine (summertime early morning cold, that is).   The cold start valve is fine.  The car runs like crap and just barely keeps from stalling for the 3 - 5 minutes until the engine really nice and warm and then it runs great. 

So the little sliding metal flap in the Auxiliary Air Regulator is staying closed even when everything cold.   I've removed it and sprayed copious amounts of carb cleaner into it and manually moved the flap open multiple times but it is not getting any better.   In fact whatever spring is in there forces it closed each time I move it open with a small screwdriver, kinda like the shutter of an old camera. 

Since my expectation is that when it's cold and no 12v has been heating up the little metal thingie to cause it to close, I'm going to assume that a spring or whatever has failed inside it since it's closed all the time.   

I assume other than spraying in carb cleaner there is not much more to be done.  It's not like it's not movable: like I said, I can open it by putting in a small screwdriver and I can pivot/slide the metal flap over and out of the way so it's wide open but the second I remove the screwdriver, it flicks back to it's closed position.

Anything else I can do?  Anyone got a working one they have for sale?  I see a few available from the US but if I can get one locally, that would be nicer.   

Thanks!
-George

[BUSDADDY]

Loosen that little nut on the stud sticking out in your top pic and turn the stud slightly (slotted end?), I can't recall which way but one direction will make it open. Careful re tightening the jam nut or you'll need a new AAR for sure.
Is the plastic thing on the end where the plug goes in loose?, if it turns the unit is toast.

[kinggeorge13]

Loosen that little nut on the stud sticking out in your top pic and turn the stud slightly (slotted end?), I can't recall which way but one direction will make it open. Careful re tightening the jam nut or you'll need a new AAR for sure.
Is the plastic thing on the end where the plug goes in loose?, if it turns the unit is toast.

I wondered about that.  I should have tried it.  I had read that it controlled how much the aperture opened but yeah, maybe adjusting it will get it to open again.   Meanwhile it's in the freezer overnight to see if that coerces it to open and if it does then I would think that gives even more credence to the adjusting of that little bolt/stud to adjust what temp or amount it opens.   Yes, the plastic plug end was nice and tight.  I'll try gently adjusting that nut this morning.   

Thanks!
-George
 

[kinggeorge13]

Pretty sure mine is not working properly but after cleaning, lubricating and cleaning again, I figured I'd do as much as I can to get it working smoothly and see if it nets happy results.  I don't think it did.  In the end, I see very little difference in how much the little slider inside is open when the valve is "cold" (as in first thing in the morning in the summer with outside temperature at 15c).  However, freezing it overnight at -18c, opened it quite a bit but I'm not really sure at all how much this should be open/closed at these temps.   Here are my photo results:

As taken out of my beetle, cold engine, outside temp 15c:


After freezing the AAR to -18c:


Sliding the adjusting nut/stud to maximum opening, this is how much it's open on my workbench, ambient temperature around 18c:


To me, this is not very open.  For fun, I put it back into the beetle and tightened the hose clamps and tried her out and the super-slow, stalling, running rough while engine still cold has not been cured.  I still feel this opening should be far more open.  I'd say it's maybe open 1/5 of the size of the orifice.   Even freezing it as per the first photo only got it open a little more than this (admittedly though I did not try the freezing test again after I adjusted the nut/stud).   

As I think I mentioned earlier, if I connect a hose directly to bypass the AAR (same idea as if the entire opening in the AAR was completely wide open), the beetle starts perfectly cold and if anything is idling wayyy too high but for sure the hesitation, stalling, all that stuff is completely cured.  That is what makes me think my AAR is not opening enough. 

Anyone seen one operating properly to compare to my photos to comment on if mine is opening enough or not? 

Thanks!
-George

[pittwagen]

Here is one from my spare 2.0 motor taken at 23deg C. an hour ago.  Never messed with, adjusted - nothing.  Did you check the resistance at the plug as per the Bentley.  Should be 30 ohms.  Mine is 30.9.  Best one ever.  Most I have had (probably 10 or so) are in the 40's or 50's. This engine starts right up idles fast and slows down to 900 or so.  Higher fast idle in the cold.  Just as it should.

Maybe you should try one from a FI Rabbit/ early Golf or Jetta.  The don't stay open as long but the initial air flow is similar.  I have looked at them all.  They all fail or work poorly at some point and the rebuilds are junk.

[kinggeorge13]

Here is one from my spare 2.0 motor taken at 23deg C. an hour ago.  Never messed with, adjusted - nothing.  Did you check the resistance at the plug as per the Bentley.  Should be 30 ohms.  Mine is 30.9.  Best one ever.  Most I have had (probably 10 or so) are in the 40's or 50's. This engine starts right up idles fast and slows down to 900 or so.  Higher fast idle in the cold.  Just as it should.

Maybe you should try one from a FI Rabbit/ early Golf or Jetta.  The don't stay open as long but the initial air flow is similar.  I have looked at them all.  They all fail or work poorly at some point and the rebuilds are junk.

Hmmmm.......Pittwagen: so yours in a cooled off state seems to have the almost exact same opening amount as mine in my photo #3.  But yours is from a larger bus engine and I wonder if that is the amount of air that a bus engine uses and a Beetle needs more, possibly?   Although the engine on the bus is significantly larger so that would seem unlikely:  I would almost think it's the other way around and the bus engine needing more air than the beetle engine.   

I had not measured the resistance but I was ignoring that because the purpose of that heating element in there was to close off the airflow through the AAR as the engine warmed up and I was pretty certain that was fine since the engine runs and idles fine when it's warmed up.   But now as I sit here late at night thinking about it, I'm wondering if in fact the resistance/heating of that spring in there is in fact whacked and maybe as soon as I start the engine it's heating up way too much too fast and closing the orifice within a few seconds instead of a few minutes.   That seems possibly hard to believe it might be doing that but I suppose anything is possible.  I will measure that resistance this morning.   Or I can go radical and just pull the electrical connector off and try starting the beetle because then I will know for 100% sure it's not heating up quickly and closing off the airflow.   

Although for fun, I looked up part numbers for the AAR and according to aircooled.net, it seems the same part number 280 140 101 was used for 1975-79 Type 1 and 1976-83 Type 2 so now I'm thinking possibly my AAR is in fact working ok since the opening amount while cooled off is seemingly exactly the same as yours.   Hmmmm....

[kinggeorge13]

And..................FIXED!!!!   So thanks to Pittwagen mentioning his "spare 2.0 motor" and my realization that later FI bugs and buses used the exact same AAR in the mid-late 70's and hey, I have a spare bus engine too!  So I went to that spare engine that's been sitting collecting dust, spiders and the odd mud-wasp for the past few years and disconnected and dug out it's oily/greasy/dirty/nasty AAR.   Cleaned it all up, cleaned it out with carb-cleaner and jeez yeah it's opening was just about double the size of the opening of the one I pulled out of my ailing super beetle.  I'd say overall it's about 50% open at room temperature.  The beetle's AAR was around 25%.   Popped it in and tightened up the hose clamps and voila, she started right up and immediately went into that strong purrrr of initial faster idle as she warmed up.  No hesitation.  No chugging slowly and stalling.  Just pure purr.   

Thanks all!

-George, Soo-Jean and Penelope the '79 Super Beetle.