Yeah, that would be nice. What about repurposing the recirc switch to manually turn on a vacuum relay that engages the air recirc pod? That way, you could just leave the ACC out of it.

If the vent flaps are controlled by vacuum pods, and there's a vacuum supply line that you could tap into, then it's likely that you could install a switch to manually control the center vent. However, you'll want to tie into a vacuum source that makes sense to tap into. If you tie something into the "always on" vacuum line, then you might have to perform two actions to turn that thing off. For example, if you have the defrost running and the center vent opened (with your custom switch), and you want to switch to footwell only, you'd have to turn the built-in dial to footwell, and you'd have to turn off your custom switch for the center vent. Most people don't like having to do two things to get one result. The nice thing about my mod is that it utilizes a vacuum source that is only on when the appropriate buttons are selected on the ACC. If you are running defrost, the center and footwell pods don't have a vacuum source because they should be closed.

Webmaster, thanks for adding this to the wiki! That's been an invaluable resource for me.

BTW, you might want to re-save the original graphic for the schematic as a GIF. Non-photographic images like that one don't hold up so well to the JPEG compression. It's a bit hard to read some of the numbers.

All 3 of my '87s have had the separate footwell pods, I don't remember what year this one was built though. I believe that production begins in May or June.

__________________

Gone to the dark side

- Jeff

As soon as I finished this write-up, I started playing with that switch that I gave up on... the rear window screen switch (124-821-04-51) with the icons that look sort of like upper and lower vents.




It dawned on me that it wouldn't be too hard to make the rocker stay in the upper and lower positions. I took some cues from the way the other switches do it.

Basically, like many other switches, this switch has a ball bearing in it that is under pressure from a spring. The ball rests in the low point of an internal vee shaped brass rocker. When the outer plastic rocker is actuated, the ball is pushed up one of the sides of the brass rocker, compressing the spring and increasing the pressure on the ball. When you release the switch, the pressure from the spring makes the ball return to the low point or center point in the switch, returning the rocker to it's central position. When the switch pushes the ball up the side of the rocker, that rocker pivots just enough for the tops of it to make contact with a metal post, closing a circuit.








The way to make the switch stay in one of the actuated positions is to keep the ball from sliding back down to the bottom of the vee. This is easily done by drilling a small hole in the side of the rocker for the ball to rest in. A 5/32" hole is just big enough to overcome the spring's pressure, and not too big to make it hard to get the ball out.






The inside of the switch actually has two of these vee shaped rockers and two ball bearings.




There are two separate small metal plates, one under each rocker with an upward bend that makes contact with each rocker. These upward bends are the pivot points for the rockers. On one side of the switch this contact is just to the right of center of one of the rockers, and on the other side of the switch this contact is made just to the left of center of the other rocker. The fact that these contacts are made off center makes the two rockers tilt in opposite directions.






I bring up this detail because when we drill holes in the arms of the rockers, the hole has to be above these pivot points. Otherwise there will be too much play in the switch when the ball bearing is "resting" in the hole - resulting in inconsistent contact between the rocker and the metal post. In fact, it's actually best to only drill one hole in each rocker, and locate that hole on the side of the rocker that doesn't contact the pivot point. Since the pivot points for the two rockers are on opposite sides, there will be only one hole to lock the ball bearings in place in each of the two switch positions (up and down). While one ball is locked in place, it will be the other ball on the other side of the switch that is pushing the brass rocker over the pivot point - making contact with the metal post.






This switch has to be wired differently than the interior dome lamp switch (124-821-02-51) I used in the write-up. Here's a new schematic:




Much Better!

Done!

- Changed schematics to GIF

- Added Addendum to include "rear window screen switch" info

__________________
Bill Wood - Retired Webmaster
My Personal Website
1998 Mercedes E430
2010 Toyota Sequoia
My Photo Albums

Thanks again Bill!