I just bought a '01 Supercrew and was surprised that it did not have "theater lighting", or slowly dimming interior lights once the door was shut.

Has anyone done any mods to add this? I would thing just by adding some sort of capacitor across the lighting circuit would do the trick.....

Any help is apprciated!!

 

Your gonna need a capacitor that will never ever completely charge off a 12 volt battery. If the cap charges you will get an open circuit and thus no light. I'd recommend a variable capacitor so you can change the timing of the dimming. You will need a capacitor that can handle more that 14.8 volts. You will have to put it in series with the dome light and tape it up real nice like and it should work great. It probably want cost more than a few dollars to do this and it will last along time.

 

Wouldn't you put in parallel across the dome light? Like an electrolytic cap which is fully charged when the battery powers the light, but when the 12v is shut off, the electrolytic cap slowly discharges and dims the light.....

 

If you put it in parrallel all you will be doing is shorting DC to ground. A capacitor acts as a short until it charges. Once it charges it acts as an open circuit. To avoid fully charging a capacitor your gonna need like an 18 volt cap. Something that can never be fully charged. You will have to put it in series. It will look cool though and do exactly what you want. A 500 mfd would probably work well.

 

What type of cap? Electrolytic?

 

Electrolytic would work fine. As for size that will depend on how long you want the light to stay on before it dimms? Just make sure the voltage is rated for the capacitor at atleast 16 volts.

 

Thanks for the help!!

One more question- If you're using an electrolytic for this purpose, how do you wire up the cap? If wiring the electrolytic in series to the light, does the + terminal go toward the battery or toward the light?

(Battery).......+CAP-.........(Light)

(Battery).......-CAP+.........(Light)


Thanks again-

 

I question the series wiring too. If you do that, you won't get any light once the cap charges...

here's proof... (video) as the voltage on the cap rises, similarily the voltage on the resistor(or bulb) decreases. To discharge this you'd have to go back to the Parallel wiring.

http://www.ac.wwu.edu/~vawter/Physic...rcuitMain.html

 

hmmm... That's kinda what I had been thinking.... Been way TOOOOO long since my basic electronics classes!

That cap in parallel would only instantly be a short to DC, and then charged. If you put a resistor in series with the cap (but still parallel to the light circuit) it would charge more slowly?

 

A capacitor acts like a battery so all you're doing is storing energy to use when the truck is off. It'll have to be in parallel with a resistor to limit current both when charging and discharging. Also you might want to think about a diode or you will have power back-feeding to the battery.

 

I'm surprised no one has done this mod before! I would think that this would have been tried before.

Or offered as an aftermarket mod.

 

Maybe my thinking is wrong. The capacitor gonna short though until it charges up in parrallel. Thus no light will go thru the light bulb will it..

 

But the light is still connect in parallel with the DC source. Those caps charge almost instantly when voltage is applied across them. At least that's how I'm thinking....

 

Your right my thinking wrong.... Your gonna need a pretty good size cap to do this it looks like...

 

That's why you would put a resistor in series with the cap. This is going to limit the current both while its charging and discharging. The cap resistor wouil be placed in parallel with the light bulb. Voltages stay the same in a parallel circuit only the current is split. In a series circuit you would have a voltage drop across the resistor and cap and the light would not light properly having less of a voltage applied to it.