CIS aux air valve resistance

[OhioRick]

I'm checking my AAV from my 1983 SC and the plate doesn't seem to move. I removed it and measured resistance at about 29.5 ohms, so it's not an open circuit. I then applied 0-12 VDC with no movement of the plate. Is it toast?

[boyt911sc]

Bosch AAR's (0-280-160-xxx) are commonly referred as AAV in some technical manuals. But in this forum we call this CIS component as AAR (auxiliary air regulator). Even in some Bosch technical booklets it is sometimes referred as AAV. Going back to you AAR, if your car is a USA/Can model it should have -218 or -226 for Euro/Row cars. A good AAR-218 has a heating resistance around 33 Ohms.

Tony

[OhioRick]

Thanks for the quick reply.

I'm in the valve business and naturally anything that starts stops or controls flow is a valve to me. I have Bosch part 0 280 140 218, and get 26.5 ohms so that seems pretty close and would indicate a good heating coil.

I just expected 12 volts to make a change, but didn't see any. Maybe I didn't wait long enough or it didn't need to move at my ambient temperature of about 70 degrees F?

after my post I saw a test in my Bosch book about the change in opening when really cold (like in the fridge or freezer) vs warm. I will try this next, but still think a "cold" engine at 75 degrees should have more opening than when hot. My current problem is the engine races when hot after idling ok when "cold". This makes me think the orifice is not changing as it warms up.

Looks like it can't be opened for cleaning without destroying the rivets holding it together. Any other thoughts?

[boyt911sc]

Rick,

Place the AAR in a zip lock bag and place it in your refrigerator or freezer for 15 to 30 mins. Make sure your wife is not around!!!!It should be opened when cold about 1/3 or slightly bigger than a quarter moon. It does not open bigger than a third. To test for closing, placing it in an over @170°F for 10 mins. or the lowest temperature your oven could be set but not greater than 200°F. It should be totally closed when you get it out of the oven.

To test if the AAR's heating system works, use a fully charged 12 bolts battery booster for the test. Three (3) to five (5) minutes would be the time needed for closing the valve and that depends on the value of resistance (Ohms). Keep us posted.

Tony

[OhioRick]

Great information. I will do that. Thanks.

[timmy2]

You should have about 12vdc at the AAR Black plug on the engine when the ignition is in the on position. Check it to make sure it has the proper voltage on it.
Air flow safety switch needs to be disconnected. Or fuel pump running by installing jumper.

[boyt911sc]

Originally Posted by timmy2

You should have about 12vdc at the AAR Black plug on the engine when the ignition is in the on position. Check it to make sure it has the proper voltage on it.

Dennis,

There will be no power at the AAR plug with the ignition switch @ ON position. The only time you could get power to this plug is if terminal #30 (FP relay) is energized. When you get power at terminal #30, the FP, WUR, and AAR would be energized. Or you have a defective FP relay.

Tony

[timmy2]

You are correct Tony, I usually test with fuel pump jumpered to run and ignition on. I edited my post.

[Walt Fricke]

If the valve part simply doesn't move despite all testing, what do you have to lose by squirting brake cleaner in from both sides, and blowing it out with air. Then penetrating oil both sides, and blow. Then maybe more brake cleaner.

And then test.

Don't think you have much to lose, but like most of us I have never had one apart.

In extremis, I suppose you could grind off the rivets and punch them out. See what is binding inside, fix that if you can, maybe some grease, or file some roughness, or something. Then do some drilling and tapping to use suitable screws to put it back together. Might be better than new - handier to service, anyway.

Or maybe Tony or someone has one which tests good to sell you.

The lower the resistance, the hotter the element around the bimetallic spring which moves the valve is. Assuming you have 12V coming in, and the ground wire has a good ground, you should be good on that part.

I wonder if the heating elements ever fail? Or, if they do, how common is that?

[boyt911sc]

Walt,

The two (2) critical components in the AAR are the bimetallic spring and the heating resistance (Ohms). Similar to the WUR, both these parts are important for the operation of this device.




Dennis,

Have you tested or used the AAR I gave you? Please advise.




Rick,

I could lend you one to test. PM me for details.


Tony

[timmy2]

Tony,
The AAR you sent is in my car being tested. I haven't noticed a difference from the one I had, but I haven't had any really cold weather to run it in since it arrived.
If you need it back let me know. I could send you the one I took out for an exchange as well. It works as it should.
Send me a PM or email.

[Walt Fricke]

Tony

I think the question is what fails in the AAR? I have trouble thinking that bimetallic strips fail. If they broke, that would do it? But is that likely? Fatigue failure from all those cycles? Do these lose rate after so many cycles? Regular springs do not lose rate, which is governed by their Young's modulus or some similar inherent characteristic of the alloy used. But they can, like old overloaded VW vans, take a set. With torsion bars you can just reset your ride height, and you are back within spec. Might that be related to the practice of tapping or pulling up the plug in a WUR?

I have even more trouble seeing the resistance coil wrapped around the bimetallic arm failing. If a wire broke, you'd have zero resistance. If insulation between wraps failed, the measured resistance would decrease. Lower resistance at the same voltage = more amps = more heat, which would mean the bimetallic strip would flex more sooner, wouldn't it? Wouldn't be a cause of slow closing of the AAR?

I suspect you have way more experience than most (certainly than me) looking at the innards of different WURs, which are pretty easy to open. What on this electro mechanical side of things do you find went wrong with ones which aren't working as they should? That should translate to the thermal characteristics of the AAR also, should it not?

[boyt911sc]

Originally Posted by timmy2

Tony,
The AAR you sent is in my car being tested. I haven't noticed a difference from the one I had, but I haven't had any really cold weather to run it in since it arrived.
If you need it back let me know. I could send you the one I took out for an exchange as well. It works as it should.
Send me a PM or email.

Dennis,

Just keep the AAR. I have a big box full of AAR's. I've been 12 months behind schedule for the two (2) engines I am rebuilding that would need engine harnesses. So you know I'll be calling on you for getting fresh engine wire harnesses.

Tony

[timmy2]

Sounds good Tony.
Don't wait too long, Porsche and other suppliers keep raising their prices and I may have to follow suit soon!