In the first article we discussed at length some basic terminology and methods to utilize in designing and laying out the addition of some electrical devices to your truck. If you missed that article, or want to more thoroughly review the content, then I suggest that you head back there first. The most important thing in that first article as it relates to this article, is noting and understanding the types of available switches.

Briefly,

• An SPST switch is single-pole / single-throw. A simple one input, on/off switch.
• An SPDT switch is single-pole / double-throw. One input and two possible outputs (or, as we'll see later, two possible inputs and one output)

In the second article I discussed circuit configurations, power sources, connections, circuit protection and routing. That article can be reviewed at http://www.geocities.com/gdgo/f150a2.htm

The importance of the second article as it relates to complex control, is understanding a 'complex circuit' configuration and the advantage of using relays.

In this third article, I will elaborate on using a different type and configuration of switches to control relay inputs for 'complex circuit' arrangements. This type of complex control is very useful for auxiliary lighting, but I'm sure you may recognize some other uses/applications.

Since I am focusing on lighting, it is important that you become aware of your specific local/state regulations regarding the installation and operation of auxiliary lighting. Forget about conjecture or opinions. As with anything else regarding your vehicle, you should contact your state department of motor vehicles to find out what the specific requirements are for your state.

That being said, when I contacted the New York State Department of Motor Vehicles, they referred me to their legal affairs office. They produced a copy of the auxiliary lighting section of the state motor vehicle code. The reg's do not state specifically how the operation of any auxiliary lighting should be controlled by stock lighting. The code is very specific as to the mounting of these lights, but was bereft of any specific control requirements. The only caveat is a 'catch-all' phrase that the auxiliary lights must not be distracting or a nuisance to other motorists. Pretty vague if you ask me.

I seriously doubt if any law enforcement officer will cite you for PRUDENTLY using auxiliary lighting. As to concerns regarding vehicle inspection, I suggest that you contact your local DMV office and get a copy of the regulations. If nothing else, if an inspection station tries to 'make up' a regulation, you can have the 'cold hard facts' available to you.

Another advantage, as you will see, is that complex controls allow you to hookup your auxiliary lights so that they operate with the appropriate 'stock' lighting as specified by local codes, AND divert control to a different source as you see fit.

Let's get back to the subject matter at hand…