Digital Multimeter Repair
- 1). Turn the meter on. If the display appears weak or if you see a "low battery" indicator, replace the batteries.
- 2). Set the meter to read resistance. Touch the test probes together and wiggle the probe wires. If you get erratic readings, replace the probe wires. Most DMMs have test leads terminated with standard banana-type connectors, so replacing them is simple.
- 3). Open the back of the meter. Locate the fuse and remove it. If it's a clear glass fuse, check to see if the thin wire inside is good or if it looks burned. If it's obviously blown, replace it. If it's a ceramic fuse that you can't check by looking at it, use another meter to test it for resistance. If it reads open (infinite resistance), replace it with another one of the same type and rating. Many DMMs use small, instrument-type fuses rated at ½ amp. Check the meter's owner's manual for the fuse type and rating.
- 4). Examine the wiring inside the DMM. There may be wires running from the battery compartment to the main circuit board, other wires leading from the probe connectors or other components. If any of these wires are broken, loose or damaged, desolder the broken pieces with the soldering iron and wick. Cut and strip pieces of new 24-gauge wire or whatever gauge is suitable for the meter, being careful to expose ¼ inch or less of bare wire to avoid shorting out any nearby connections. Solder the new wire in.
- 5). Examine the insides of the meter, looking for loose screws, nuts and other hardware. Sometimes metal parts can work loose in heavily-used test equipment, shorting out or making connections erratic.
- 6). Reassemble the meter. Set it to read resistance and touch the probe tips together. The meter should read a very low resistance, 1 ohm or less. If the meter still has problems, consider replacing it.
Source...