Troubleshooting Chargers with a Multimeter
Make sure the charger is disconnected from both the AC power AND the battery.
Battery chargers have 3 distinct parts, the Primary AC (input from the AC power outlet), the secondary AC (output from the transformer), and the DC output.
For chargers without an auto stop/start module:Primary AC:
Turn AC power switch on, and touch meter prods to the live prongs on the AC plug. If there is continuity, the primary AC section should be good. There should be NO continuity between either live prong and the ground prong. If there is no continuity through the live prongs, you need to investigate the ON-OFF switch, the AC circuit breaker or fuses and the connections to the transformer. The switch and circuit breaker can be tested by removing the wires to them and testing for continuity. If there is no continuity, that part is bad and needs replacement.
Secondary AC:
This portion consists of the transformer secondary winding, the coarse and fine control switches, and the two yellow wires that lead to the rectifier. The coarse control switch has 4 wires leading from the transformer to the switch in the lower right-hand corner of the machine, and the fine control switch has eight wires leading from the transformer to the switch in the center of the front panel. To check this entire mess, place both meter leads on the yellow wires comming from the switches and turn the knobs to make sure there is continuity in all positions. (This requires all three of your hands. the small multicolored jumpers sold by Radio Shack are nice to hold one of the leads in place.)
DC Circuit:
Most of the problems with a non-functioning charger are to be found here. This section consists of the rectifier (the one-inch square block the yellow wires lead to), the ammeter (usually not at fault), the ballast resistor (frequently at fault), the fuse and fuse holder (fuse is frequently at fault) and the DC output leads (frequently at fault...hold clamp in one hand, wire in the other and pull. If wire is broken, clamp will pull off of clamp).
Place multimeter leads on clamps, red to red, black to black. There should be continuity. If there is not, one of the above listed parts or the wires connecting them is open. Now reverse the leads. There should ne no (or very little) continuity. If there is continuity, then the rectifier is shorted and needs replacement. Need more help? Call me. My name is Penny. (954)587-8084 or e-mail me below. Back to Main Page