LiftMaster RSL12U RSL12U Troubleshooting Guide Manual - Page 24

MODEL LA400U SYMPTOM: Operator does not have power. POWER OUTLET HOUSING (Back of Outlet Housing) Incoming Power Outlet * CONTROL BOX CONTROL BOARD CONTROL BOARD DIAGNOSTICS 4 Check the control board.* Try replacing the fuse. If that does not work, replace the control board. Outlet Incoming Power 1 Check the incoming power.* Check breaker first, then check wiring coming into operator. The reading should be 120 Vac. HOT GROUND NEUTRAL Black Green White J15 Plug 2 Check the transformer.* Check the voltage coming from the transformer (red and black wires at the CHARGER terminals). The reading should be 34 Vdc (+/- 10%). If not, replace the transformer. Battery 12V 7AH Battery 12V 7AH Red Black Black Red 3 Check the batteries.* Check the battery connections. Make sure two 7AH batteries OR two 33AH batteries are connected in series. Check the voltage coming from each battery by disconnecting the battery from the operator. A fully charged battery should read 12.8 to 13.3 Vdc per battery. If not, replace the batteries. 23