Replacing Halogen bulbs with LED's

[BenC]

LED lighting fixtures in general , like fluorescent fixtures, cannot be dimmed via reducing the voltage to the light like halogen and other incandescent bulbs are dimmed. The dimming scenario for LED's has been the biggest holdup in their wide-spread usage in high-end coaches. Special circuitry is required to dim them that reduces the current flow, NOT voltage to the light.

Vantare coaches utilize a dimmer resistor network to dim the salon ceiling, galley ceiling, bath ceiling, and bedroom ceiling lighting. Sequential pushes of the switch add more resistors in line with the bulbs to get the dimming effect you have. The LED lights would/will work fine on the full bright setting (bypassing both resistors), but the 2nd and 3rd stage will cause premature failure to the LED fixture if left in that condition for long and will not work correctly, if at all. Think of it this way, LED assemblies are electronic appliances that produce light, they are not simply lighting fixtures like a halogen bulb. Electronics do not like/function properly with low voltage or high voltage conditions. Hope this helps.

[Ray Davis]

So, I assume that Marathon coaches with their progressive dimming would have the same issue?

[BenC]

Unfortunately, you are correct. Pulse-width modulation or resistive dimming both have the same net result, which is low voltage to the light fixture.

[Ray Davis]

Thanks Ben, I had been contemplating changing to LED bulbs, but didn't realize they had this limitation. I don't often dim them, however I wouldn't want to burn things out accidently either. Those LED fixtures are still pretty pricey. I was more concerned with lower power and less heat ...

[Roadpilot]

I have a Millennium that has dimmable LED lights in place of Halogens. They work great and throw off no heat. An LED light is a light emitting diode that is forward biased. It would br preferable to dim it by reducing the current through it since it's forward voltage curve is relatively steep (not as steep as a silicon diode though). I know for a fact that if you reduce the current through an LED you will not kill it, you will increase it's life and it will dim. You could keep the current constant and modify the time it was on. And to the eye it would look dimmer.

[BenC]

The aspect that "kills" the fixtures is the reduced voltage, and the problem is not generally with the LED (PN junction) but with the descrete circuitry used by the particular manufacturer to obtain the 1.2volts across the PN junction (depending on the material it is made from) for electron flow across it, producting the desired light output. I have seen failures in which resistors or descrete components were burned out, and depending on the manufacturing process, components could be replaced. More often than not, however, the assembly is non-serviceable without destroying the casing and/or the assembly.

Some fixtures can be dimmed and "work" for a while. Premature failure will occur, however, and because of the high cost, is not the best option.

The choice is always up to the individual. I just want to supply information so individuals can make informed choices.

[Roadpilot]

Gee, I'm glad to know that my dimmable LED's are going to die shortly. Millennium will be happy to install dimmable LED's for anybody that wants to save the heat of Halogens and the pain of replacing bulbs. Also glad to hear my four roof AC units are about to die.

And oddly enough, among other things, I am a pilot.