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We've got 12V halogen G4 fixtures mounted under our kitchen cabinets and would like to use LED's instead. I found some G4 LED bulbs on Amazon, and they fit in the fixtures just fine, but if I try to replace more than one of the halogens with the LED's, they won't fire up (they just barely come on at all).

On a circuit with two fixtures, if I have one LED and one halogen, they light up just fine.

Any idea what is going on or what I need to do?

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are the lights on a dimmer circuit. if so, it sounds like your dimmer is not rated for LED's and needs the extra current draw from one of the halogens. –  Hightower Jun 29 '14 at 19:11
Nope, these are not on a dimmer circuit. –  Scott Jul 1 '14 at 0:01

2 Answers 2

You probably need to replace the power supply with one designed for LEDs. According to various web sites:

  • You aren't putting DC-only LEDs in an AC system, right?
  • Some LEDs have compatibility issues with transformers designed for halogens.
  • In particular, the power supply may have a minimum load and your all-LED setup uses too few watts: "When replacing with LED bulbs they found they had to keep at least one halogen in the circuit to keep the load high."
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Are all the fixtures connected to one ballast? In any case the the power supply or driver needs to be changed. You will need a driver that is rated in Current and voltage to match the number of lamps you connect to it. If you can share the current and voltage rating of the Led lamps purchased I can help you with that. Noor

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