Installation Instructions

First: this control will only work with a negative ground wiring system.
The ignition source should come right off your ignition switch, that is, this powers the control only when your ignition is on. This, of course, should be a line that is already fused. If the ignition switch is hotwired directly to +12V, you should install an inline fuse. You can also use the accessory position, but you should be aware that the headlamps can come on without the motor running.
Ground: nothing special required here, just make sure you connect to a good ground, or the control will be unpredictable and unreliable.
Please note: if your wiring is dodgy, the control WILL be unpredictable and unreliable.
Headlamp Output: 12 Volts (20 Amps max.) will appear at this terminal when the control module is activated, either by the photocell detector or the wiper "on" input. Wiring considerations will be discussed at length later.
+12V Constant: This should be a fused, un-switched source, that is, 12 volts will always be on here. This is a required connection. This is the source of the +12VDC output, and should be capable of handling the load. The headlamps are not powered from the ignition line.
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: This is not connected to anything inside the control, and you can use it as a place to make other connections, or, install a wire loop and hang the control with a tie wrap.
Wiper Input: this should be connected to the wipers at either the normally open side of the wiper switch, or from the wiper motor itself. The objective is to have 12 volts appear here when the wipers are turned on.
Wiring the headlamps: Although there will be just one wire coming from the control module, you have to realize that when you turn on the headlamps with the dashboard switch, this activates several other circuits first, such as taillamps, parking lamps, instrument lamps. 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.
Some Notes on Operation and Your Vehicles Charging System:
You know, I really love my 60 year old truck, but I also like the convenience of my wife's Town Car. This headlamp control module was designed to make the convenience and safety of the Town Car's lighting system available to other vehicles. But, it is still a 60 year old truck and cannot be like a new vehicle. When making your settings for this control, you should consider the capability of your vehicle's charging system. The more the headlamps are on, the greater the draw on the electrical system. If your re-charging system cannot keep up, the result is going to be a dead battery. This is a consideration for the two available adjustments: the light level upon which the control turns the lights on and the shutoff delay. The more the headlamps are on, the greater the demand on the charging system to top up the battery. If you have an original generator, it probably won't keep up. Everything is a trade off when using an older vehicle. If you want the module to turn your headlamps on at dusk, maybe you will have to put the battery on a trickle charger once a month to keep it topped up. Or, you could set the control to come on only when it is truly dark. This is also a consideration when deciding on the shutdown delay. Running the headlamps without the motor running really pulls down the battery pretty fast. You could ask for a shutdown delay of a minute and a half, which will really kill your battery, or settle for having the lights on for just 15 or 20 seconds. I just wanted to mention this because it is a consideration for my 60 year old daily driver.