Heating Vent Selector.

[z_ya]

It controls nothing, it makes no sound or moves heat to different vents at all. The vehicle is a '78 280Z. When moved to air con though it will do something. Right now it seems to be stuck on everything for vent selection it comes from the defrost the floor the main console vent and even the sides. Has anyone else had this problem or can anyone aid me in to fixing this? Thanks in advance guys.

[SteveJ]

You may get better responses if you either take off the control panel and describe what you see (pictures help) or download a copy of the 78 factory service manual (FSM) and go through the diagnostics and report results.

[Wade Nelson]

Yeah, ok, I've been down this road. Start by going to O'Reilly Auto and buying twenty feet of their smallest vacuum line. It's like 7/64" or something like that.

There's a DISC beneath the dash with six barbs (nipples) on it that control all the vacuum motors that move all the vent doors.

Chances are you've got one or more vacuum lines either off their barbs, or with holes in them, and at least one or two failed vacuum motors.

so SOMETHING is letting the vacuum "escape" and nothing else works.

So start by re-plumbing FROM the vacuum source in the engine bay to the dash. Install a one-way check valve.

Next, take a piece of hose, and attach it to one vacuum motor at a time, suck on it, and see if the motor works.

Most motors have two barbs. one for partial pull, one for full pull.

Post again in two weeks and let me know how it's coming. Plan a trip to the junkyard to obtain replacement vacuum motors.

Oh, and go check out my OTHER thread on fixing these problems...

http://www.classiczcars.com/forums/interior-280zx/46770-diagnosing-hvac-control-vacuum-leak-glovebox-removal-tip.html

[TomoHawk]

He's correct. the heating system on a 280Z relies on vacuum and vacuum pods to operate things. Unless the vacuum pods are broken, you need to check that all the hoses are in good condition and connected properly. For reference, I have used "fast Frog's vacuum diagram" as a guide. Even my radiator shop guy said it was better than what he could find on his computer system.

BTW- fastwoman posted a writeup on how to service the vacuum selectorhttp://www.classiczcars.com/forums/engine-drivetrain-s30/35521-refurbishing-hvac-vacuum-selector-valve-1978-280z-useful-info.html

Wade-

What kind of vacuum pods do you look for? I think I need one to operate the fresh air door on my '78. Please keep some notes on where you find any compatible units, as that will be a popular item one for these cars.

Edited January 30, 2013 by TomoHawk

[Wade Nelson]

>What kind of vacuum pods do you look for? Working ones.

The last two I needed (and purchased) came from a guy parting out a ZX in the classified sections here. I got lucky. He removed them without damaging them and they worked.

Without extensive, extensive fabrication, duct tape and bailing wire trying to retro-fit some other vacuum pod would be a nightmare.

I bought ONE at a junkyard and found it was failed as well. Same one, fresh air door vent.

Of course, Nissann no longer stock's 'em.

On the ZX all three pods are different, mirror images in one fashion or another. So you can't swap one for another. It's a nightmare, couldn't

they have designed the damn HVAC to use three of the same, identical pod!

I really think the solution for SOME of us is lawnmower throttle cables hidden beneath the dash so you can have summer/winter modes.

[TomoHawk]

>I really think the solution for SOME of us is lawnmower throttle cables hidden beneath the dash so you can have summer/winter modes.

I was thinking that too. Wiring it shut for the winter would be fine, but not for the summer. An electric solenoid to operate the fresh air door, maybe?

[Wade Nelson]

standard vc292 | eBay

If I were gonna try and adapt one, I'd probably start with this...

[Captain Obvious]

If you aren't planning to use the A/C, then another option is to switch to the non-A/C control head.

It doesn't use vacuum at all. Everything is controlled by cables.