A/C recirc check valve and diff check valve = two check valve on same line?

[Jonas_R]

Ok,

Trying to figure out way my Zeitronix map sensor does not see any boost it turns out that somebody has connected the ECU line to the A/C recirk check valve in the engine bay. So that is why ecu does not see boost.

However can some please tell me the following:

According to this diagram from Paul the pink line sits before the A/C recirc check valve and goes to the diff. However the A/C recirc check valve has built in t-piece on the vacuum side and the pink line is supposed to be connected there. So why do we have one more check valve?

I'm missing something or perhaps the 3B does not have a built in t-piece in the check valve?

Dave any comments?

Paul original Diagram for 3B:


Modified diagram for 95' model ABY:

[Error404]

It's because they each have their own vacuum reservoir

[Jonas_R]

But if they are on the same line why do they need two check valves? Can't wrap my head around it.

[quattro-nick]

i think it's just for protection

[Jonas_R]

Yeah that makes sense I guess.

[Jonas_R]

Edit.

I think I have figured it out know.

The two black lines on the ac record valves goes to the reservoir and the recirc it self.

Then pink line goes the diff before any check valve and therefore it needs its own check valve.

And my car is missing the green vac line it seems.

Just great I guess another thing to fix on the list.

[UrS4boy]

G71 MAP sensor and Moisture trap info.

Ok, Trying to figure out way my Zeitronix map sensor does not see any boost ]

And my car is missing the green vac line it seems.

Yup. No green line to the ECU (via the moisture trap), no boost.

G71 MAP sensor info: http://forums.quattroworld.com/s4s6/msgs/20417.phtml

Moisture trap info: http://forums.quattroworld.com/s4s6/msgs/20401.phtml