so I have decided that my contractors cap on my truck needs some lighting inside. I have 5 doors so I will have 5 lights and 5 momentary on off push button switches. so if one door is open one light is on. here is the tricky part. I want it set up in a way that if any one of these switches is activated they will turn on an indicator light on my dash. I can get it to work if I put 5 indicator lights in the dash, but I only want to put one light in the cab of the truck. I think 5 indicator lights will look awful. anyone know what I need to finish this system? any suggestions are appreciated

 

Diodes. Because your going to have to run a long wire I would use the switches to connect to ground. At the switch run one lead up to your lights and another to a diode which will run to the front lamp. Do this at each light and when one is activated, it will light the lamp and indicator but not the other lamps.

 

You could do like I did for my cargo lights and just put 1 lighted pushbutton switch on the dash under the headlight switch. It's easy to quickly reach from outside the truck.

Hook all your lights to the switch so that when you hit the switch they all come on and saves having to hit a switch each time you open a cargo door.

I picked up this round pushbutton switch at Radio Shack:

 

Just use double pole switches. One pole to the light, one to the indicator in the cab. It can't backfeed if the other switches are off.

 

Heck, the dash light just needs to be mounted in series with the lights in the back, and the lights need to be in parallel to each other. One way to do this:

power> dash light> to long run wire to back> splice into 5 wires>>>>> 1 wire to each switch>to each cap light >ground

There is power at the dash light and at each switch at all times, but you only complete the circuit once you close a switch which sends power through the switch to the bulb to ground. You may want to wire this hot all the time, or hot in run - depends on your pref. Only hitch to this is that you won't get the full 12v to the lights in the back since the indicator will cut the voltage some, being in series. Make the indicator as small wattage as possible, and upsize the cap light wattagess to help compensate. But this is the simplest method I can think of.

 

Problem with that scenario is if the indicator light blows, none of the rear lights will work. Installing higher wattage lights in the rear to compensate for the voltage drop at the indicator will surely blow the indicator, since all current needed to run the rear lights will have to run through the indicator. It may not blow with only one light on, but it definately will with 2 or more.

 

Hmmm - you're probably right there. I think the general principle is correct, but it needs a tweak. Probably a case for a resistor bypass shunt: put a large resistor inline with the indicator and a smaller one in a shunt bypassing the indicator light. The smaller resistor would take the bulk of the current. A ratio of 10:1 or 100:1 on the resistors would probably do the trick, but the smaller resistor would need to be rated to carry a few amps. Sorry, but it's been a looong time since I had a circuits class...

But frankly I like Greg's solution best: 1 switch hits them all. Then just use a switch with an indicator light in it.

 

Just for my information, Why doesn't anyone want to use diodes?

 

ReAX,
You are correct. The correct and safest way to wire this config. is with Diodes. You can use any general purpose rectifier diode 1N4001-1N4004 series. The lighting circuit should also use NC (Normaly closed) switches if they are to be momentary. (with the doors shut they will be open circuit, doors open, closed circuit.

 

run a power relay it can supply 20-40 amps that is plenty of power .

 

Most likely they don't know how they work. Diodes is definitely the way I would do this.

 

thanks alot guys I am gonna go pick up some diodes. and get this wired up within the next week or so when I get it all done I will let you know how it turns out