545svk

Hi, there is a mysterious vacuum line under my center console, that is blocked of with a screw.

I traced it to a white vacuum line coming out through the firewall behind the fuse panel.

There is vacuum in the line with the engine running.

Any thoughts where this should go? Or what the PO may have had connected to it?

Thanks

jpitman2

The heater controls are operated by vacuum, so I think it will be the feed to the climate control manifold.
jp 83 Euro S AT 56k

MainePorsche

The white line goes to the heater valve off the HVAC solenoid panel. Below is a pic of the solenoid with the vacuum lines to and from it.
Also is the link to Dwayne's HVAC write up. http://dwaynesgarage.norcal928.org/1...0Procedure.htm

545svk

^^Thanks Maine. I'll check, but my white line from the vacuum solenoid seem to go up behind the instruments. Plus the heater work.

I'll try and trace the line from the engine side as well.

Hilton

There is no vac line which comes through around the ECU panel on an S4. I figured its not the one for the HVAC as that does indeed come down from the right side of the console.

My guess is a PO had a vacuum gauge, or a mechanic was trying to run a new vacuum line to the HVAC because of HVAC problems (and because of not understanding how 928 HVAC works), and it just got left there.

WallyP

Didn't some years have a vacuum advance unit on the ignition ECU?

MainePorsche

We didn't know if the attachments to the solenoid were intact, and all were accounted for. Your heater will work without vacuum by default - the valve won't close without it and you'll never get cool air. Also was thinking some PO rerouting, but these two Smart Guys maybe onto to something.

Petza914

Was or is your car supercharged? If so, might have run to a boost/vac guage like I have in my console. Any other wires near it. Boost guages are usually used in conjunction with AFM gauges.

545svk

Thanks for all the input.

I know very little about the car's history but it "feel" like it was added for some reason.

I want to check all the under bonnet vacuum lines so will hopefully find where it was connected in.

I was briefly wondering about whether it may have something to do with the headlight height adjusters?

Wisconsin Joe

No. Those lines run from the adjuster **** (down by the parking brake lever) directly up to the front.

They are white, nylon "hard lines", not black rubber vacuum lines.

Good thread, including pics:

https://rennlist.com/forums/928-foru...-overhaul.html