Pentair light not working

[sandmellison]

I have a Pentair light that uses the 12 volt 300 watt r40 bulb. The light stopped working, I pulled the fixture and replaced buld. The old one was definitely blown. Tuned power back on and no light. Tested transformer output and have 12.8 volts, tested at deck junction box and have about the same. Pulled light fixture out again and removed bulb and tested at socket again 12.7 volts. I have tried 3 different bulbs none work. Any suggestions? Getting a bit frustrated.

 

[1poolman1]

I have a Pentair light that uses the 12 volt 300 watt r40 bulb. The light stopped working, I pulled the fixture and replaced buld. The old one was definitely blown. Tuned power back on and no light. Tested transformer output and have 12.8 volts, tested at deck junction box and have about the same. Pulled light fixture out again and removed bulb and tested at socket again 12.7 volts. I have tried 3 different bulbs none work. Any suggestions? Getting a bit frustrated.

Sometimes the small tab at the center of the socket gets pushed down by a bulb, or the new bulb doesn't have enough solder at the center of the part that threads in to reach. It can be raised slightly with a small piece of stiff wire.
Also, check for continuity of the bulb between that center solder and the brass threads. Bulbs can be bad even though new.

 

[sandmellison]

Tried that already. Just connected a fourth bulb directly to transformer, no light. Have 12.8 volts with bulb in circuit. The bulb did start to get warm but no light. The only thing I can think of is that the transformer isn't putting out enough current.

 

[Hansenaz]

If you measure 12V across the bulb it should light (transformer is delivering enough current to maintain the voltage drop). Either you're not actually measuring the voltage drop across the bulb or the bulb is defective. Try it with a different 12V source.

 

[sandmellison]

Update: Replaced 300 watt transformer. Tested and still no light. Pulled apart switch box that was just below transformer and noticed one terminal on switch was loose, melted and wire insulation was burnt off for about 3 inches. When I jiggled connection the light came on. To be safe I pulled 2 new wires from switch to the junction box near pool, hooked all back up to a new switch, hooked up light fixture and tested. It worked! Or so I thought. Turned back off via the switch, turned back on and nothing.
Today I installed a new pentair light fixture using a 50 watt (300 watt equivalent) LED. Same bulb I was just using. All is now working and I am glad this nightmare is over.