HVAC - vacuum lines

pedroj · Post by **pedroj** » Sat Jul 29, 2017 7:58 pm

Hi,
have a 92 EA81 Brumby, have been working my way through all the little issues with the heater and vent control. Okay so have the heater control sorted, nice warm air now or nice and cold when aircond is on.
Also today have found the source of all my vent control issues (missing retainer clips on the drivers side levers and arms), so the last one is the control of the Fresh/Recirc air controlled by the two push buttons on the dash.

It would appear there should be a source of vacuum coming in from the engine bay to be controlled by the switch behind the dash buttons, that then actuates a plunger behind the glove box to control a fresh / recirc flap on the fan box.

When I trace what I thought was the incoming hose as it passes through the firewall into the engine bay, instead of going to the motor / manifold it goes over to an actuator on the drivers side strut (next to the aircon relays), then a hose off the other side heads to an actuator on the side of the carby for what I believe is fast idle when the aircon is on. I am lost as to how this should work for the Fresh/Recirc actuator in the car, the fast idle part seem to work okay though.

It would seem there has been some - re-plumbing going on some where on my car, which does not surprise me as lots of things on this brumby are just put together wrong, maybe a mad scientist had it before be and it was an experiment in KAOS assembly

Can anyone describe where their vacuum line from the pair of dash buttons goes to and from?

Regards,
Peter

pedroj · Post by **pedroj** » Sun Jul 30, 2017 11:22 am

update,
have found a previously not seen black plastic tee piece in the vacuum line just near a fixing point in the left (passenger side) of the engine bay, so now I have located where a line from the manifold (?) SHOULD be connected but have no stray hoses of that size (5 mm ?) so it would seem it has been completely removed and its source plugged up (hopefully not just left to be a vacuum leak).

So my query is now, where on your car does the thin vacuum hose go from that connection? is it to the side of the carby some where or a connection on the manifold? There is a likely spot on the rear of the manifold low down but it looks to have never had its cap removed.

It is nice to be one step closer to having another small niggle fixed but need assistance from a form member to get the last part of my puzzle done

Peter

Silverbullet · Post by **Silverbullet** » Sun Jul 30, 2017 11:50 am

The vacuum source for the fresh/circ switch should just come straight from the manifold. There should be a 6mm or so brass barb somewhere on the passenger side of the manifold for you to hook up the hose to. The T piece to the solenoid on the strut tower would be to supply vacuum to the "idle up" solenoid for the A/C. This is so that when you push the A/C button, some vacuum is used to pull on the throttle slightly and raise the idle for the increased load of the A/C compressor.

If your hose just went straight from fresh/circ switch to the idle up solenoid, I'm willing to bet your engine idle doesn't pick up when you activate the A/C?

*Edit* Just read your post again, the fast idle works? That is confusing

There must be vacuum coming from somewhere for that to work.

pedroj · Post by **pedroj** » Sun Jul 30, 2017 12:01 pm

Hi Silver bullet, might have had my self confused with fast idle on air con... but will look for that barb and see what I find as one on rear of manifold has never been off.

Peter

pedroj · Post by **pedroj** » Tue Aug 01, 2017 4:07 pm

a person on the Subaru facebook group was kind enough to post some photos of his car, it shows the line from the manifold is twice the size as I expected then after about 200mm it goes to an adaptor to reduce its size down to what I could see leaving the firewall and continues on its trip. As this area is hard to get into without removing the air cleaner (I have aircond compressor and hoses in the way) I could not easily see what was in there. So will have to source a reducer as well it would seem, probably from the wreckers.

Peter.

pedroj · Post by **pedroj** » Tue Aug 01, 2017 4:12 pm

Oh, as a side issue if you find your sliding leaver for HVAC vent control will not go completely to its end positions, remove the drivers side Demister duct and check out the mass of plastic leavers and cogs to see what is out of wack. In my case the flap for the demister duct on the drivers side had broken a clip and was fowling the mechanism because it was out of position.

Made a new clip from some scrap steel plate and it is smooth as silk now and all the flaps open and close like a bought one, plus I get demist on both sides of the windscreen Woo Hoo

Another job that has bugged me for ages completed.

pedroj · Post by **pedroj** » Thu Aug 03, 2017 9:26 pm

Turns out the VAC line from the manifold is 4mm ID, this then needed to go to a 4 to 2 mm reducer before it goes to the T piece near the firewall via a section of the 2mm ID vac line.
Connected it all up tonight and I now have vents that change from Fresh to Recirc and my fast idle on the air cond actually pulls in as it should.

No idea why a previous owner stripped this all out.

Regards,
Peter