My Clock is Busted!
The
clock in my car was inoperative when I bought it. The previous
owner had a piece of electrical tape to cover it up because at
night, it put out a lot of light and had smears of the remants
of the LCD still displayed. So I decided this location was perfect
to mount the Air/Fuel Ratio Meter (ARM1).
Removing the glovebox and dash panel wasn't too
difficult. One just has to remember that there are overlapping
pieces and hidden screws. With the age of the plastic, it's quite
brittle so you want to be careful. Easiest to remove the glove
box first. Then remove the cover plate at the end next to the
door. You'll find two screws for the dash panel. Also two more
under the pop-off cover next to the air vent. Then there's one
hiding under the air intake next to the cigarette-lighter. Gently
turn the grill counter-clockwise and pull it off to access the
screw. The final two hidden screws are under the temperature controls.
Remove the slider knobs and pry off the upper black cover. You
can leave the clear cover on. Be very gentle!
Cannibalizing the Clock
Remove all the felt surrounding the clock. It hides
the mounting screws and tabs. I then enlarged the hole evenly
all around with wire-clippers to roughly the size of the ARM1.
Then I finished the job with a wood rasping file and finally,
a precision needle file. The next tough part was figuring how
to mount the ARM1 into this opening. Then it hit me! I've got
a clock that fits perfectly, why not use it to mount the ARM1?
So I remounted the clock in the dash and drew a
centerline across the face where the ARM1 would line up. Then
I removed and mounted the clock in a vise and hacksawed out the
center section just thick enough for the ARM1. I then filled the
top & bottom halves with epoxy to give a flat surface to hold
tape. I used the thin double-sided tape used for photographs (not
the foam kind). Be sure to line up all the pieces first, making
sure the ARM1 protrudes from the dash surface just the amount
you want. Also save the circuit board from the guts because we'll
use it later to hook the ARM1 into the existing wiring harness.
Hooking Up the Power Wiring
As luck would have it, the wiring going to the
clock contains all the ignition-on power, ground and night-lighting
signals we need to hook up the ARM1. This is how they line up:
| Clock Harness | ARM1 | |
| green --> | ON power | <-- red |
| brown --> | ground | <-- black |
| grey --> | dash lights | <-- white |
I ended up cutting these wires 3" from the back of the ARM1 and soldering it to the PC board cut out of the clock. This allowed the unit to be plugged straight into the car's wiring harness without cutting, soldering or crimping.
Hooking Up the Oxygen Sensor
Wiring
Well, I wanted to keep things as clean as possible,
so I hooked up the ARM1's sensor wiring directly into the DME
wiring at the connector. I tucked the remaining two wires (EGO
signal & ground) high above the glovebox and wrapped it around
the DME harness near the firewall down to the DME computer. I
didn't want to risk shorting the EGO cable (coaxial-type shielded)
by using vampire taps. So that means connecting to that wire inside
the DME connector itself. I opened it up and threaded the sensor
wire and ground under the rubber seal.
The signal from oxygen sensor comes
in at Pin-24 and I found a good ground at Pin-28. Actually the
ground was 0.005V below the chassis, so I'm not sure where the
electron sink is coming from, but it was stable, so I used it.
Taking out the metal pin to get a good solder joint can be tricky.
Pull gently on the wire with needle-nose pliers and release the
catch tang with a small screwdriver. Kinda wedge the screwdriver
tip towards the outside and you should feel a little "click"
and the pin will release.
Then, you can unclamp the strain-relief and feed
in the sensor & ground wires. Clamp back down tight and solder
the joint. Make sure that the catch tang on the pin is bent back
out so that the pin will stay put when you re-insert it into the
connector. Then put the side catch plates back in and reassemble
the connector. Zip-tie the rubber boot and that's it!
The Finished Product !
After everything's reassembled, the ARM1 installation
into the clock opening looks pretty good. Like it came from the
factory that way. No messy extra wiring and no drilling of the
body. Now it's onward to installing the ARC2 fuel-controller...
Troubleshooting
)
One of the most common problems that may arise
after installation is that the ARM1 display doesn't behave as
it should. How should it behave you ask? Well here's
how:
idle - display should dither around
the middle yellow dots (when engine is warm).
medium-throttle less than 3500rpm - should
also dither around the middle, but encompasses larger group of
dots.
larger-throttle above 4000rpm - display
should stop dithering and hold steady, slowly creeping upwards
full-throttle - display should be at 1st
blue dot (last green is too lean, 2nd blue is too rich)
coasting in gear - steady on 1st red dot (computer
has shut off fuel, you should feel shudder around 2000rpm as fuel
is turned back on)