Air Conditioning/Power Steering Valves

[bucko]

I recently picked up a Valve setup along with it's electric vacuum pump, tubing, and hose. This setup bolts up along the passenger side engine firewall side.

In studying this setup, it appears that 12 volts will get sent to the vacuum pump, which creates a vacuum which operates the valve, and then what? It also appears that the cloth tubing from the valve connects before the air flow meter. The purpose is to raise the idle when the air conditioner or the power steering pump is equipped and/or working.

Was this setup used on both the 1.9's and 2.1's equipped with AC and/or power steering?

My 84 1.9 had air conditioning at one time, and a previous owner removed most of it. I'm in the process of adding it all back, and am wondering if I need to add the valve once the AC is working. I still have the power steering, and there are none on these valve setups installed, and the engine idles just fine. I remember seeing this discussed once here by TENCENTLIFE, but I cannot recall the topic he was refering to.
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Current VW drives: 1984 Westfalia

Past VW drives: 1967 Beetle, 1973 Beetle, 1977 Bus, 1971 Military Type 181

[tencentlife]

Well,you can always search for anybody's posts and a keyword. I find stuff that way all the time when I remember that I or someone else had posted about some subject.

What it seems you're talking about are the idle boost valve(s) used before the late Idle Speed Control system on '86+ vans. The late system is able to meter bypass air and get idle speed feedback, so it's an all-in-one solution. The only shame is that it wasn't integrated into the ECU. As an add-on, it requires a lot of additional wiring that is prone to the same age-related troubles that plague the FI itself.

Before '86, they added one or two solenoid-actuated bypass air valves, one each for AC and PS as the van was equipped. There is no vacuum pump involved, so I don't know what you are describing. They were simply plumbed so that each one could open and allow a fixed volume of metered intake air to bypass the throttle. One was powered right off the AC clutch power, and the other was powered by a high-pressure switch on the PS pump. The PS switch only closes if PS pressure peaks above the normal level, which normally will only happen when you turn the steering to full-lock. That puts enough strain on the pump that it could stall the motor at idle, so the valve allows a little extra air to compensate so the engine can make a little more power at idle. The AC valve is doing the same thing, compensating for the extra torque load whenever the compressor is engaged at idle.

You can see how the AC valve is wired on Bentley p.97.138. The valves and plumbing are shown on p.24.24b.

You'll want to have a working valve when you reactivate your AC, or the engine may stall when the compresor cycles on at idle. As for the PS, it's only needed when you turn to full lock, otherwise the idle is tuned for the normal PS pump torque load anyway. If you're not in the habit of turning the wheel to full lock while idling , you will never miss the valve.

[[email protected]]

the pump sounds like the cruise control pump? nothing to do with the AC or PS
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Markus

[bucko]

I'll post a picture of the setup today. There is a "gizmo" that has a "+" and "-" on it, and it looks like a small vacuum pump of sorts (reminded me of the pump for an aquarium). This pump has a tube running to the valve that then plums into the large plenium before the AFM.

Again, I'll snap a photo.
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Current VW drives: 1984 Westfalia

Past VW drives: 1967 Beetle, 1973 Beetle, 1977 Bus, 1971 Military Type 181

[bucko]

"......Before '86, they added one or two solenoid-actuated bypass air valves, one each for AC and PS as the van was equipped. There is no vacuum pump involved, so I don't know what you are describing. They were simply plumbed so that each one could open and allow a fixed volume of metered intake air to bypass the throttle."

The solenoid-actuated device is what I was refering to when I said it resembled a vacuum pump. So it looks like vacuum runs to this solenoid, and it is opened (via the 12 Volt and ground connection I mentioned) allowing the valve to open and allow "a fixed volume of metered intake air to bypass the throttle".

So, this fools the ECM by making it "see" more air, and therefore it enrichens the fuel mixture to bump the idle?
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Current VW drives: 1984 Westfalia

Past VW drives: 1967 Beetle, 1973 Beetle, 1977 Bus, 1971 Military Type 181

[tencentlife]

A common misconception. It's a throttle bypass. That just means it allows already-metered air to go around the throttle body. It's exactly the same effect as if the throttle was tipped open a bit. It's not a matter of altering mixture, it's just a way of raising engine speed , by allowing air to be routed around the throttle body ( the "bypass"). The air has already come thru the AFM, so it has been metered and the ECU injects fuel accordingly in the proper ratio according to the present engine temp and rpms.

If you look at the drawing I mentioned, you'll see that the valves are plumbed in parallel with the Aux Air Regulator, which also acts as a throttle bypass during warmup. The AAR and the boost valves all get air from a fitting on the intake elbow which is after the AFM, and they each allow air to then enter the intake plenum directly.

[bucko]

I can't speak for anyone else, but I find this interesting. I always figured the ECU needed the throttle position switch's reading to adjust the throttle RPM; once that switch was open, the AFM readings kick in and/or took over.

I see now that the ECU can be fooled into reading metered air using this valve setup. So, if the large black rubber boot had rips in it, this could cause a higher idle too I suppose, much like how a vacuum leak caused higher idles in carb'd engines (depending on where the vacuum leak was).

I wonder how many of these setups were removed, thinking they were causing a foul idle situation by uneducated mechanics and others?
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Current VW drives: 1984 Westfalia

Past VW drives: 1967 Beetle, 1973 Beetle, 1977 Bus, 1971 Military Type 181