Originally Posted by zebellis

Sometimes. It's more of a problem without the mod because if a passenger is colder than you, cranking up the heat will heat up the footwell compartment pretty quick. With the mod, I can just shut off the footwell vents and direct the center vents towards the passenger.

Originally Posted by zebellis

8) Pry back the carpet under the armrest with a screwdriver being careful not to use the wood panel as leverage - as it will likely chip or crack.




9) Unscrew the exposed screw.
Put the shifter into reverse or drive (with the car off!).
Lift up on the panel and it will hinge at the front until you can pull the panel off.






10) Remove the fader switch. If you are using this option, then it's likely that you've already been messing with these wires to access the speaker wires.
In any case, you need to pull the wires down through the bracket holding the window switches, and out into the open area near the shifter to get them out of the way.
This may involve cutting or unsolder the wires.
Do this at your own risk! I did this last year when I replaced my stereo, so I don't have any photos.
The gray/blue wire that powers the light in the switch will come in handy with our new switch.




11) In the back of the glove box compartment is a group of wires that lead to the glove box light.
Carefully remove a few inches of the sheath.
Tap into one of the black and yellow striped wires to get power for our vacuum relays.
Run the wire under the vacuum switchover valve (Y7) and through to the center console compartment where you will be installing your switch. 4-5 feet of wire should be enough.




12) You could use the brown wire on the lead to the glove box light for ground, but I chose to run a new wire to the bolt holding the black cross-member to the frame.
If you want to do it the hard way (like I did), you'll need to remove the passenger side vent, and move the large air duct out of the way (it's actually not that hard).
The vent has four spring tabs holding it in place.
Using four small screwdrivers or coat hanger wire, pry the bottom spring tabs up and the top ones down enough to release pressure on the surrounding dash.
The vent should slide out, but it may take some persuasion. Carefully disconnect the illumination bulb.



View through the passenger side vent opening



13) The ground wire only needs to be long enough to reach into the center of the glove box opening, but with plenty of slack.
This is where our new vacuum relays will go.
There's plenty of space between the cross-member and the side vent air duct to tuck the relays so we can get the glove box back in.
You'll need to split this wire off so that we can make two ground connections - one on each of the vacuum relays.

14) On the front of Y7 are numbers 1-7 corresponding to each valve. Number 3 goes to the foot-well pod, number 4 goes to the center pod.
Disconnect them, making a note of which is which (you might want to label these if you want to undo everything).

15) Using the photo, cut your hose pieces and put everything together to match mine.
It's very important to install the check valves.
At any given time, one of valves #3 or #4 on Y7 will be open to the air via the open ports on the back of Y7.
The check valves will prevent Y7 from sucking a vacuum through one of our new hoses connected to #3 or #4 and getting unlimited fresh air from the open port on the back of Y7 for the opposite valve.
That would prevent the vacuum suction from getting to the pods.
It's also important to leave the top valve on our new vacuum relays open to allow air to flow through to the vacuum pod when we want to turn that pod off (by energizing the respective vacuum relay).



16) I'm not sure if it matters which side of the vacuum relay you connect ground to, but I just did whatever was done in the car that I took the vacuum relays from. (You can also look in your own car).
So, in that case, connect a ground wire to each vacuum relay using the pin on the same side as the part numbers.
Connect a separate wire to each of the other pins (on the same side as the little diagram), and run these two wires through to the center console compartment where your power wire went earlier (step #11).

17) Tuck the vacuum relays, hoses, and wires down in the space at the bottom of the glove box compartment between the black cross-member and the black air duct.
I tucked all the hoses with the check valves under the bracket holding the cross-member, and left the original hoses going to the vacuum pods above that bracket.
Do whatever works for you, but be careful not to disconnect the center vacuum line from the rubber angle connector that leads into the middle of the air box where the center vent pod lives.
You should be able to see this with the ACC unit pulled out of the way (see picture in step #6).





18) You can test your creation at this point.
The key is to use a setting on the ACC that you know will produce air from either one of the center or foot-well vents.
Turn the car on and press one of the non-defrost buttons on the ACC unit (warm the car up if necessary).

None of the three wires you pulled through the dash (one hot and two from the vacuum relays) should be connected to one another - this way air should be coming out of both of the center and foot-well vents.

If you connect one of the relay wires to hot, that vacuum relay's solenoid should energize and turn off flow to it's respective pod - stopping the flow of air to that vent.
Try it with the other wire to test the other vacuum relay.

Continued...

Originally Posted by zebellis

Now we're on to the switch.

This next section will depend greatly on the type of switch you are going to use.

If you're not using the same type of switch that I am, then you're on your own.

The only thing you need to know is that with the way the vacuum relays are configured with the hoses, powering the relay will stop the vacuum flow to the pod, closing the flap.

If your switching solution requires that you do the opposite (energize the vacuum relay in order to send vacuum to the pod, opening the flap), then you just need to move the hoses from the bottom (valve #1) of the vacuum relays to the top (valve #2).

Leave the hoses connected to the right angle valves (#3). This document, page 8, helps describe the vacuum relays (they're called vacuum switchover valves).



You can install the switch as is, but the way we're using it, the illumination LEDs do not work when the switch in is the "up" position.
So we need to install a new ground pin to separate the illumination circuit from the switch circuit.
Steps #19-26 are optional, but I recommend them.
If you want to skip them, then I would not recommend connecting an illumination wire to this particular switch.

(OPTIONAL - but recommended)
19) Pry off the cover of the junk wiring harness.
You should be able to easily remove any one of the sockets, keeping the wire attached.



20) Pry off the cover and base of the junk switch you have.
You need to remove one of the pins. Find one that can easily be disconnected from the inner wiring, unsolder where necessary.
Usually the pin connected to a resistor or an LED is easiest.
Others may be pressed into metal plates or washers.
In either case, the pin is press fitted into the plastic and can be very hard to pull out.
I found that pressing the hot soldering iron against the exposed portion of the pin will heat it up enough to melt the plastic around it just enough to ease its removal.
You could also cut the plastic around it.
Once the pin is out, set it aside with the socket from the last step.

Here's the switch I used for the pin:


Pry off the bottom:


This is an easy pin to remove.
Just unsolder the resistor and heat the pin to melt the plastic surrounding it.
Slide it out.


21) Now pry of the one side of the cover of the wiring harness you got with your new switch.
You'll need to pry off the side with the numbers 1, 3, and 4.
Add the socket you removed in the step #19 to spot #4.
Close the clip.





22) Take the new switch and remove the top cover, keeping in mind how it goes back on.
Look inside and take a picture or note how it all fits together.
Remove the ball bearing and any loose springs, set them with the top.
(I didn't have any photos of the switch before I altered it, so I used a newer version of the switch with the same insides for these next three photos.)




Watch out for these ball bearings, shafts, and springs.
They will fall out.


23) Flip the switch over and remove the bottom (gray plastic) by prying with a very small screwdriver to lift the plastic case free from the four little tabs.
Be careful not to break the plastic.



24) Find the hole labeled #4 in the bottom of the switch.
Take the pin you removed in step #20 and press it firmly into that empty hole from the top.
Be sure it's in there very tight.

25) Notice how one lead of the LEDs is soldered to the metal strip connecting pin 1 to 5.
Carefully unsolder this lead. Use some small needle-nose pliers to bend the lead over to your new pin in hole #4.
Solder it to that pin.




26) Put the switch back together.
Make sure it fits into your wiring harness.

27) If you are installing the switch into the lower console in place of the fader switch, you will probably need to shave off a small amount of plastic from the four little ridges on the sides in order for the switch to rest low enough in the empty space left by the fader switch.



28) Feed the wires of your wiring harness through the appropriate opening above the ACC unit (or in the fader spot).
Connect the wire like this:

• pin 2 (gray/blue): power for the illumination - find one to tap into, usually a gray/blue wire, I used one from my old fader switch
• pin 4 (what ever color you got with your socket): ground for illumination - again, I used one from my old fader switch
• pin 3 (two brown/white wires together): hot from the glove box light (or other source that's only on when the key is in the "accy." "run" or "on" position) - this powers our vacuum relays
• pin 1 (brown): connect to the vacuum relay for the footwell pod
• pin 7 (brown/blue): connect to the vacuum relay for the center pod

29) Test the switch.

• When the switch is in the upper position, it energizes the footwell vacuum relay and no air comes out of the footwell vents.
• When the switch is in the center position, neither of the vacuum relays are energized and air comes out of both center and footwell vents.
• When the switch is in the lower position, it energizes the center vacuum relay and no air comes out of the center dash vents.

If the upper and lower switch positions do the opposite of what is described above, just swap the wires to pins 1 and 7.

30a) Remove the plastic thing covering all the wires to the switch harnesses behind the switches.
Press in the four tabs (two above and two below the switches).
It's a tight fit behind there, but it's flexible so just work it out to the right and down.



Insert your new switch wiring harness (without your switch plugged into it) in through the back of the empty spot above the ACC unit.


If you need to move or rearrange any switches, the harnesses will come free if you apply a little pressure with a screwdriver on each side of the harness.


-OR-

30b) If you are putting your switch into the fader switch spot, first rest the switch into the empty spot and make sure it rests level with the passenger window switch.
Cut extra off the plastic ridges (see step #27) if necessary.
Put the switch into the harness and clip it up onto the back of the wooden console panel (just like the fader switch did).
I do not have any picture of this.

31) Tuck all wires out of the way and put the ACC unit back in place.

32) Install your new console panel with the opening for your new switch (or if you used the fader spot, screw the lower console panel back in place).

33) Put the glove box door back on, followed by the glove box liner (don't forget to pull the wires for the light out through the opening in the liner), then the latch at the top of the liner.

34) Enjoy!

-Zeb

Originally Posted by W124 E300D

that's what I didn't get... here passenger and driver have their own, individual and separate, thermostatically controlled vents / areas... as standard.

Originally Posted by zebellis

I see that in many newer cars. I don't know too much about the difference between US and Euro versions, but is it a simple matter of region, or are those differences model dependent?

Originally Posted by zebellis

is it a simple matter of region, or are those differences model dependent?

Originally Posted by zebellis

It's actually not hard at all. It took me way longer to make the write-up than it did to do the mod. It helps to have all the stuff acquired first.

The flap for the center vent is buried in the air box and would require taking the dash off to access it. Check this out. I would definitely NOT do the first option you mentioned. Yikes! The second option would be a lot easier - disconnect the hose from valve 4, cap valve 4, run a new line from the hose to a tee on the white supply line.

Sometimes. It's more of a problem without the mod because if a passenger is colder than you, cranking up the heat will heat up the footwell compartment pretty quick. With the mod, I can just shut off the footwell vents and direct the center vents towards the passenger.

Originally Posted by whunter

A well written DIY, thank you for spending the hours writing/editing it.

This DIY has been sent to webmaster@peachparts.com for the PeachPartsWiki
.

Originally Posted by Webmaster

This DIY is now in our Wiki HERE.
Thanks!

Originally Posted by babymog

I am now thinking about controlling the left and right footwell vents separately, ... the early '87s can do that and I have a spare early '87 HVAC assembly! Fun fun fun.