Installation Instructions for Module P#: BI HM(A)12V-30A 12/2003
A note on the adjustments. Both potentiometers are 15 turn (total) units.
Both have been preadjusted. Pot A is set at about 9T clockwise, and Pot B is
about 3 1/2T clockwise. Be very careful adjusting these pots. Once they are
at the end of a travel adjustment there is a slight resistance to turn further.
Do not force it! For safety reasons, you should never try to leave an
adjustment at the end of the pot's travel. If you think you are at the end
of travel, always back the pot in the reverse direction by at least 1/2
There are 2 adjustments available: Pot A (the one NOT in the corner) controls
the light level sensing. Turning this counter clockwise makes the module
come on later, that is, it needs to be darker to turn on. Turning the
pot clockwise makes the module trigger earlier, meaning less dark.
Pot B is in the corner of the module and it controls the ignition off
shutdown delay. Turning this counter clockwise shortens the time the
headlites will be on. Turning it clockwise tells the module to keep the
lights on longer.
Refer to the wiring diagram. Connections are very straight forward. The
supply line (12V constant) MUST be a fused line (30 A max) that is always
on. The headlamp terminal will have 12V appear here when the module triggers
on. Wiring this terminal to the headlamp terminal on the light switch may
NOT turn all the lights! It depends on the internal wiring of the switch itself.
You could just bring this lead to the headlamp connection on your
light switch, but you probably want the other circuits to be on also. There
are several ways to do this. One would be to make up jumper wires and wire
all the connections on the light switch together, but then the switch would
no longer work as originally set up. There would no longer be a parking
light position, as all the circuits are now tied together. This is a minor
inconvenience, but it is something to think about. A more elegant method is
to wire the circuits together with power diodes. They would be arranged so
that the headlamp circuits (which is the last to come on at your headlamp
switch) would power up the other circuits, but these other circuits will not
power on the headlamps. A diagram is provided __here__ for your convenience. We have
an optional diode stack, already wired together, for your convenience.
Photocell: Hide the photocell wherever you wish, but it must be exposed
to the ambient light level. Please be aware that the leads directly behind
the cell are fairly fragile, so the cell should be handled with care until
it is in place. Some suggested locations are: above the dashboard in one of
the holes around the vents, rear package shelf area, just behind the grill,
in front of the windscreen in the area of the wipers. Make sure that the
cell and wire immediately behind it are not going to be moving around. You
can secure the wire in place with a tie wrap just behind the cell, with the
cell above the tie, as the cell itself weights almost nothing. It is not a
good idea to do this horizontally though, as the cell might start to flex
the leads and break off. You can also secure the cell in location with some
RTV, but make sure the wire behind it is tied in place and not tugging on
the cell. It is not a good idea to use a cyanoacrylic like Crazy Glue as
these adhesives, generally, are not moisture resistant.
Terminal G has no internal connection, so you could make a wire loop,
cinch it here, and hang the module with a tie wrap.
Terminal H is wiper input, if you want the lights to come on with the
wipers. You want 12V to appear here when the wipers are on. This could come
from either the switch, or the motor itself.
If in doubt, ask! Call us at 800 431 1384. Your comments and suggestions
Advanced instructions for setting the light sensing level.
Setting Pot A to change the turn-on threshold can be time consuming
because of the 8 second delay between the "on" trigger and the headlamps actually
coming on. You can do it over a period of time by tweaking the Pot A,
1/2 turn at a time.
For professional builders, setting the light sensing level can be done
very accurately (and fast) using really good meter like a Fluke 78.
The power for the module itself comes from the ignition on input, so if
you put a sensitive ammeter in the input line, you will be able to see when
the "ON" command kicks in.
The module draws about 3.8 mA when inactive. When the light level reaches
the "ON" setting point, additional circuitry becomes active, and the draw
jumps immediately to 6+mA. You will be able to see the threshold
immediately on the meter, and ignore the 8 second delay. The only trick is to
get the light level at the point at which you want the control module to
turn the headlamps on. We use one layer of a clean paper towel over the photocell
to set it here.
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