<e34> HOWTO: parked car ventilation

[Bob Knight <bob@xxxxxxxxxxxx>]

So you've read everything you can about parked car ventilation. You've
futzed with your OBC timer button in myriad combinations, hoping that
just once, once, you'll see "VENT". You've read about others'
frustrations and successes. OK. I'll stop.

My '90 535i now has parked car ventilation. It now works as
advertised. I'm a very happy guy. Hopefully, if you've been lusting
after this feature, you'll be happy, too. Because it is NOT rocket
science. It takes about $15 worth of parts plus I'd guess it'll take
about 2-4 hours of your time depending on how familiar you are with
how to remove and replace the:

      . glove box

      . glove box cover

      . passenger front (by firewall) foot venting and the
      associated cover

      . radio

      . OBC

You also, I believe, should have a rudimentary understanding of or
facility in DC circuitry, Ohm's law, counting and soldering. The
second may not necessarily be a requirement. You should know how to
read Bentley wiring diagrams, if only to understand how this fits in.

My disclaimer: I do not warrant that these instructions are
correct. I furthermore assume absolutely NO responsibility, fiscal or
otherwise, if you decide to do this procedure and end up frying
something in your car.

So, let's proceed. You'll need an assortment of tools and
miscellaneous stuff, not necessarily limited to:

          . hex key to remove radio

          . Phillips screwdriver

          . Needlenose pliers

          . Diagonal cutting pliers

          . Soldering iron

          . Good tin/rosin solder

          . Supply of 14 AWG stranded wire. I'd recommend red,
          black and green insulation

          . "vampire" wire connectors for connecting a wire to an
          existing wire without cutting the existing wire

          . Radio Schlock 275-218 DPDT relay (an SPDT will work,
          also)

          . An ohmmeter (DVM, preferably)

Before you start work, REMOVE THE NEGATIVE BATTERY TERMINAL FROM YOUR
BATTERY and ensure that your ignition is in the off position (remove
the key). If you don't, you may only blow a fuse. But you could
possibly blow your OBC. Or something else. Given Murphy's ubiquity and
caprice, you'll likely nail something (or things that are) very
expensive.

Procedure:

    . Remove the glove box and set it aside (see Bentley's, 513-4)

    . Remove the glove box cover (three Phillips screws: as you
    look towards firewall, right, left near glovebox latch, left
    near rear), disconnect the light and the switch. Don't break
    the plastic tabs at the rear. Slide it towards you. Set it
    aside

    . Remove the ventilation duct and cover (see Bentley's 640-12,
    figure 25). Set the assembly aside

    . Remove the radio

    . Remove the OBC by pulling the lever at the left rear of the
    OBC towards you. The OBC will pull out from its connector (26
    pin IDC)

At this point, you have access to the OBC connector and its associated
wiring. The wires of interest on the OBC connector are connected to
pins 21 (black/white or black/white/yellow, my car was the latter) and
9 (red/yellow, direct from fuse f20). The Bentley calls out OBC pin 14
instead of 21. Do not believe the Bentley. It is wrong. Pin 20 is
likely not connected, but if it were, it serves as a timer trigger for
heating. But I digress.

My car was built in 7/90. It doesn't have a sword, it has a resistor
pack. It also has the newer HVAC control. I only paid attention to
wiring diagrams EWD-125 to EWD-127. A cursory glance at the '93 wiring
tells me that this procedure MAY work with the 1993.

Now for the relay installation:

    . The OBC connector at the rear of the panel slides to the right
    for removal

    . Cut the cable tie holding the OBC wire bundle to the green cover
    for the IDC connector. Take care to not cut any wires

    . "vampire" a 15" or so wire (I used white) onto the
    pin 21 wire. Call this wire w7.

    . "vampire" a 15" or so wire (I used red) onto the pin
    9 wire. Call this wire w8.

    . find a power wire that's always on that has sufficient ampacity
    (at least 15 amps). There are a number of candidates relatively
    nearby. Carefully connect this wire (call it w3) to the hot wire
    and run it to where w7 and w8 are.
    
    . you will see a 3 pin molex connector bundled with two 4 pin
    molex connectors mated with only one green wire connected to
    each. Disconnect the four conductor connectors.

    . One of these green wires goes to the blower switch, position
    2. The other goes to the resistor pack. Ring 'em out. The latter
    should always have resistance on it relative to ground. Call this wire
    w5. The former will show open if the switch is in position 0. Call
    this wire w1. I used green wires for w1 and w5.

    . You should now have five wires, labeled (you did that, didn't
    you?) w1, w3, w5, w7 and w8. Grab the relay and figure what pins
    are which. The wire numbers that have been assigned correspond to
    the connector numbers on the relay. If you wish, sleeve them with
    heatshrink tubing of an appropriate diameter before connecting
    them to the relay. Solder them all into place. Ensure you haven't
    inadvertently bridged any connectors. Flow the solder! You don't
    want any cold solder joints here. Trim excess strands of wire away
    from each solder joint. Slide the heatshrink down flush to the
    relay and shrink it, if you used heatshrink.

You now should have the parked car ventilation feature in place, once
things are reconnected.

    . Reassemble the OBC IDC connector and its cover with a new cable
    tie. The "junction" part of the cable tie should be on the same
    side as the socket side of the connector.

    . Slide the OBC connector back into place. Ensure that it "clicks"
    into place.

    . Ensure that the OBC removal lever is set fully towards the
    outside of the dash. Slide the OBC into place. If you feel
    anything but mild resistance, DO NOT FORCE THE OBC INTO
    PLACE. Check out why its not going into place.

At this point, you can test the installation. Reconnect the negative
battery cable. Turn the ignition to position 1. Press the OBC timer
button. You should see "VENT" on the OBC display. If you press the
"S/R" button at this point, the two LEDs on the timer button should
flash and the fan should come on. If you press "S/R" again, the fan
should come off. The OBC display will change to "VENT on" and "VENT
off" on the button presses. Turn the key to position 2. You should be
able to operate the fan normally with the fan switch. Turn the switch
to position 0 and then to position 1. Press the OBC timer button
twice. You should see something like "00.00amT1" on the OBC
display. Enter a time using the "powers of ten" buttons. "S/R" should
set the time and the left timer LED should illuminate. Hitting timer
again will bring up the t2 display, which is programmed
similarly. "S/R", after a timer has been programmed, toggles its state
(eg. if it's enabled---LED lit---and "S/R" is pressed, the timer is
disabled). The timer turn-on time is not affected by the disable.
When you're done, disconnect the negative terminal of the battery.

If the above doesn't work as stated, you've got a problem. It is very
likely a wiring mistake.  Disconnect the negative terminal of the
battery, if you have not done so. Go through the instructions again,
checking your work. Check fuses, especially f20 and the fuse for the
wire you tapped for the other "always-on" 12v. Check that the relay
contacts are not touching each other or something else. Be meticulous.
Be patient. If you get frustrated, walk away from it and do something
else. Have someone else check your work. You'll eventually find out
what's wrong.

You've tested things and you're satisfied it works. Time to button
things up:
       
       . replace the radio

       . replace the ventilation duct

       . replace the glove box top cover. Ensure that you reconnect
       the switch and the light

       . replace the glovebox

Enjoy.

If you encounter any problems with the above procedure, please correct
it and let the list know.

Cheers,
Bob

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End of bmw-digest V9 #2170
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