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A switched vacuum supply for the Marelli ECU is not shown the "S60" supplement from Jaguar. Towards the end of the publication, in the "components" section, it shows the vac supply coming from the A-bank intake manifold directly to the bulkhead where it (apparently) enters the cabin along with a wiring harness
What color wires will be attached to the gizmo in question? That might be a good clue !
So possibly the narrow red tube IS the vacume pick up for the AC. As that might be switched. I looked on some really old pictures I had to try and see what is going on... A red/orange tube/pipe connects to this vacume switch.
It can't be the EFI ECU as that takes off from the balance pipe. And it can't be the cruise take off, as it is on the front. It can't be extra air, as that isnprovided vianthe EAV on the right hand side and is connected to the lower intake manifold area.What else needs vacume apart from:
EFI ECU
Marelli ECU
Cruise
AC
Tranny
If I remember correctly, the plug to the blue solenoid has a black and a white cable.
So, this wouldn't leave me alone. I remember, as I emptied my engine bay of all parts that would be in the way, I removed the little tiny harness with the blue plug. Part: DAC6536. According to Jaguarclassicparts this harness was ONLY fitted to the rear of the car... Well, can't believe that
So, this blue plug goes onto the mystery solenoid. Result: according to the tag on the harness, it is the IGNITION harness. After looking through my handy (but older) book, it is actually a vacuum (and I noticed I have been spelling it wrong all the time *doh*) timer magnetic switch. And it ONLY leads to the ignition module under the dash...
So, we have one connector for the ignition (on a Marelli!), one for the tranny and one shared one for the vacuum switch (the full throttle switch) and AC system...
Having finally had a chance to have a look at the Vacuum Manifold, this is what I can tell you.
The Vacuum Manifold as Viewed over the drivers side Wing/Fender of a UK Car
Looking at the Two Tubes that are Closest to the Drivers Side Front Wing/Fender.
The Tube off the Top Spigot goes into a 'T' Piece
The Tube at the Highest End of the 'T' Piece goes into The Firewall
The Tube at the Lowest End of the 'T' Piece goes into the White Plastic 'Gizmo' with the Blue Wire.
The Tube off the Bottom Spigot (The Spigot Underneath) goes into a much thinner Tube the goes into the Blue Switch.
Now for the Two Vacuum Spigots which are on the other Side of the Two I've just described.
The Top One (The Offside One) is Blanked OFF
The Spigot underneath it (Also on the Offside), goes to the Gearbox Modulator.
The 'T' Piece off the Top Nearside Spigot goes to a 'T' Piece.
The Top Part of the 'T' goes into the Firewall
and the Bottom Part of the 'T' goes into the White Plastic 'Gizmo' with the Blue Wire.
The Spigot underneath it goes into a very thin Tube which goes into the Blue Switch.
Part of the 'T' Piece which goes into the White Plastic 'Gizmo' with the Blue Wire.
The other Part of this 'T' Piece goes into the Firewall.
The Two Spigots on the other side of these Two
The Top One is Blanked OFF
The Bottom one goes to the Gearbox Modulator.
I know mine is a different
year, but hope these pictures may be of some help, a bit "fuzzy" but can still make out things
the electric connector on mine went from the vacuum solenoid to the Auxiliary Air Valve. when I replace the vacuum lines, I eliminated the plastic connectors (except for the "Y" connector, and did a straight run