Troubleshooting a 12V System

Entire system will not operate

  • Check 120-volt outlet to ensure you have power to outlet.
  • Check the on/off switch on power console to be sure it is on.
  • Check or reset circuit breakers on power console.
  • Check low voltage cable connection at power console.

Circuit breaker on power console trips

  • Check ends of cable to ensure copper strands are not touching.
  • Check connection of cable at power console to ensure copper strands are not touching.
  • Recalculate total wattage to ensure that you have not exceeded rated wattage of transformer.
  • Check for other shorts at fixture connection points.

Fixture will not light

  • Check lamp for broken filament.
  • Check lamp for proper fit in socket.
  • Check connector to cable to ensure that pins have pierced insulation into copper strand.

Fixture has moisture build-up inside

  • Check to ensure that shrouds and lens rings are installed properly.
  • Check that gaskets are clean and no debris is between the gasket and housing.
  • Check drainage holes for blockage.
  • Check watertight fittings on inground fixtures.
  • Refer to installation instructions for exact fixture.

Fixture on, but dim

  • Check lamp connection in socket.
  • Check connection to power cable to ensure that pins have pierced into copper strand.
  • Recalculate voltage drop to ensure that it does not exceed 2.0 volts.
  • Check total wattage calculation. Use lower wattage lamps or remove 1 or 2 fixtures from circuit.

Fixtures dim at end of cable run

  • Shorten length of cable or
  • Run second parallel cable half the distance of the first run and move several fixture connections to this second cable.

More troubleshooting information courtesy of FX Luminaire:




No power at plug Tripped breaker or GFI Reset circuit breaker in main panel or the GFI usually located in a bathroom, garage or kitchen.
GFI keeps tripping Ground problem or defective GFI GFI’s are notorious for nuisance tripping. Use a high grade model such as the Hubbell #GF5252I.
Transformer is cycling on & off at night Excessive wattage load or short Reduce lamp wattage, fixture quantity or increase size of Transformer. See shorting solution below.
PhotoCell Transformer is cycling on & off in the daytime Photocell wiring incorrect Reverse the hot and common wires on the Photocell 120v input. Request wiring schematic for proper wiring.
One cable run not working Cut cable or short Test cable for voltage – if none then it is cut – if there is very low voltage and the cable is hot then there is a short. Check all fixtures and splices for defects.
Lamps are burning out prematurely Excessive voltage at lamp Drop the affected cable run down to the next lower voltage tap or increase wattage load on that cable to drop voltage. Also, some lamps are rated for a very short life such as the 4414 (300 hours). Use halogen lamps.
The closest lamp to the transformer is burning out prematurely Excessive voltage at lamp The closest lamp will always have a higher voltage reading than the last lamp. Cable fixtures so that there is about 40′ from first to last within a lighting zone. See System Layout for details. If there is only one lamp (fixture) very close to the transformer then use 16 gauge cable to run to it only. This will help by creating voltage loss caused by the resistance from the skinny cable.
Lamps have a yellow or golden tone Voltage too low Move affected cable to the next higher voltage tap or reduce load on cable. If possible run additional cable to first fixture to reduce voltage loss.
Lamp goes on and off when fixture is moved Too much tension on socket leads With spring type sockets it is important to leave some slack so the socket contacts make a good connection to the lamp base. This is a common problem on downlights where the installer doesn’t leave any slack in the socket lead wires coming out of the back of the fixture then he tries to adjust the beam angle thereby yanking the contacts off the socket base.
All of the lights on the system are getting dimmer with age Splices are corroding As non-waterproof splices corrode they create electrical resistance which reduces voltage. To fix simply dig up all splices on the project and waterproof them silicone filled wired connectors. Black tape don’t get it!!
Photocell Transformer is coming on too soon Transformer is in dark location In order to operate properly the photocell must have a good look at daylight. Move to a brighter location.
Fixtures have a white mineral deposit on them Irrigation water is hitting them when they’re on – like washing a car in the
hot sun
To avoid having mineral build-up schedule the irrigation to come on after the lights have gone off. This is especially true with the 50w spots – very hot. To remove the deposits use Lime Away bathroom cleaner or equal.

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