How to Repair an Electronic Multimeter
With reasonable care an electronic multimeter will usually last for many years. However, there may come a time when the device doesn't work the way it should, and you will be left with the choice of repairing the multimeter or tossing it. However, before you go out and blow $20 to $100 on a new replacement, use the simple techniques below to remedy many common problems in electronic multimeters.
Step 1 - Check the Battery
Try to power on the electronic multimeter. If the multimeter will not power on at all, or if the display is very dim, the problem may be a weak or dead battery. If that is the case, simply replacing the battery should fix the problem (Note - Some multimeters come with an indicator that tells you when the battery is low. If the low battery indicator is on, change the battery as soon as possible).
Step 2 - Test the Probe Leads
If the multimeter powers on, but you are not getting accurate measurements, the problem could be with the test probe leads. In order to check, set the electronic multimeter to read resistance, and then touch the ends of the probe leads together. You should get a reading of 0 ohms (or infinity ohms if working with an analog multimeter). If you get resistance ratings that are more than 1 ohm, or you receive very erratic readings, you will be able to correct the problem by installing new test probe leads.
Step 3 - Disassemble the Electronic Multimeter
If you still haven't been able to fix a problem with your multimeter, you'll need to open it up. There should be a few small screws that will allow you to open the case of the multimeter. So, remove those with a small screwdriver.
Step 4 - Check the Fuse
Once you have the multimeter open, find the fuse and remove it. If the fuses is of a clear glass type, look inside the glass casing to see if the very thin wire inside the casing looks intact or if it looks burned out. If it appears to be blown, replace it. If your multimeter uses a ceramic fuse, you will not be able to check it by merely looking at it. So, take another multimeter and check the fuse's resistance. If there is no resistance, replace the fuse. Look inside the multimeter owner's manual to find the exact type of fuse you need.
Step 5 - Re-solder Broken Wires
While you have the case open, look for wires or connections that appear corroded or broken. If you find damaged connections, desolder them with a soldering iron and wick, and then create new solder points with your iron.
Step 6 - Check for Loose Parts or Screws
Check for any other loose parts of screws that might be rattling around inside the case of the multimeter, and fix problems as needed.
Step 6 - Reassemble the Multimeter
Put the multimeter back together. Then, set the multimeter to measure for resistance, and touch the probe leads get-together. Once again, the measurement should be well under 1 ohm. If the multimeter still does not work, consider buying a new one.