A. Generally indicates lamp cathode heat is missing. Problem source must be identified and corrected.

B. In humid weather or when air conditioning systems are operated only during working hours, dust on the lamps may gather condensation and prevent reliable starting. Lamps and fixtures must be cleaned and the lamp waxed with a good silicone wax.

C. Energy saving lamp, ballast combinations will not reliably start near or below 60°F; all others 50°F unless low temperature systems are used.

D. Indicates ballast thermal protector is cycling. May be the result of high ambient temperature, fixture misapplication or restricted air circulation. With recessed fixtures, check to be sure insulation has not been placed directly on the recessed fixture body. With surface mounted fixtures mounted against insulated ceiling, make sure they are rated for such applications.

All service checklists detail the more probable problem causes. It is important to keep in mind that other elements may be involved or more than one cause present. All electrical service work must begin with a careful and detailed evaluation of the problem and thorough inspection of all components, paying special attention to all wiring connections.

The ability to field test ballasts is very limited. The normal verification is to substitute a known good ballast in the problem fixture.

On rapid start systems only, cathode heater voltage may be verified by a voltage reading between the contacts on each socket. (A voltage of 3.5 to 5 is considered normal.)

Caution - Voltages in excess of 500V may be present between the lamp socket parts and ground.