How to Troubleshoot Using an Electrical Schematic
- 1). Know the problem that you are trying to solve and then locate all the components that could cause that problem on the schematic and highlight their interconnections. Troubleshooting with a schematic does require some understanding of how the device operates. For example, your wife's clothes dryer spins normally but doesn't get hot; unless you know how thermostats, thermal fuses, timers and power selector switches function, the schematic won't be of much help to you. A schematic is a tool to use in conjunction with a service manual.
- 2). Download and print out the schematic given in the first reference so you can follow along.
- 3). Set your Digital Multimeter (DMM) to the Ohms range and clip one of its test leads to the L1 terminal on the dryer's power cord terminal block.
- 4). Turn the dryer's timer to a normal heating setting.
- 5). Using the other test probe, move progressively and systematically through the circuit starting with the "R" terminal on the timer until you reach the "L2" terminal on the power cord terminal strip.
- 6). Watch the Liquid Crystal Display (LCD) on your DMM. You're looking for zero "0" Ohms between "L1" and "HT3." If you get an open circuit reading at "R" the timer is defective. Zero Ohms at "R," but an open circuit (infinite resistance) at "HT3" indicates a defective operating thermostat or a broken wire between the timer and the thermostat. To determine which it is, simply remove the other test lead from the "L1" to "HT1." If you still get an open circuit reading, the thermostat is bad.
- 7). Proceed systematically through the circuit until you get an open circuit reading. Once you reach terminal "H2," you will pick up a reading of seven to ten Ohms. That's the heating element's resistance and is normal.
