I have an issue with my digital multimeter (Flir DM66). It won't read resistance. I've tried reading dc voltage and continuity, both work fine.

But when I try resistance, it shows 0.8 when touching nothing, and then when I touch the probes to the resistor it gradually decreases to zero. This happens the same, no matter the resistor value.

I've replaced the batteries, checked the fuses, tried different probes, same result. The resistors are new and unused.

Any idea what could be wrong?

  • 2
    \$\begingroup\$ It could be broken. Have you or someone else done things that might damage it? \$\endgroup\$
    – Justme
    Jan 22 at 15:52
  • 1
    \$\begingroup\$ ... for example, did you try to measure resistance on a powered-up circuit. (Bad.) \$\endgroup\$
    – Transistor
    Jan 22 at 15:54
  • 3
    \$\begingroup\$ Sounds like it is shorted internally. Send it back to the manufacturer for repair. \$\endgroup\$ Jan 22 at 16:06

2 Answers 2


Any idea what could be wrong?

Whatever is wrong, here are a few common ways to go about it:

  • it's under warranty and you can have it replaced for free (or whatever the warranty terms stipulate),

  • it's in a corporate setting with a centrally administered T&M maintenance - talk to them,

  • it's outside of "paper warranty" but the jurisdiction you're in has longer warranty terms than the paper would suggest, get it replaced still under warranty,

  • it's a personal device, you don't have enough experience to safely fix it (the input circuits are safety-critical), so look for a replacement - whether used or new, doesn't even need to be FLIR,

  • it's a personal device and you know enough to fix it - then you'd be probably tearing right into it right now, and asking specific questions

  • it's a personal device and you're willing to at least do some troubleshooting before deciding how to proceed - here's what I'd suggest then.

Buy an identical, working device. It can be used, in bad cosmetic shape - as long as it generally works. Then compare component/circuit point measurements side by side, in circuit. As long as both devices have the same engineering revision, or the differences between the revisions are minimal, it may be as simple as making ohmmeter and diode measurements between various circuit points to narrow it to a failed discrete component or a chip.

If you go that route, you'll have much more specific questions, and those will be quite on-topic here. When asking, make sure that there are clear, high-resolution pictures of both sides of the PCB, with obscuring mechanical parts removed.

And, worst case, you can put the "guts" of a cosmetically wrecked device into yours, and have it fixed and looking nice for still less than a new replacement would cost.


Here is one sure shot method for repair:
Return the meter to the manufacturer's Service, Repair and Calibration group listed on the
Teledyne FLIR page. On that page see the link line under "For EXTECH and FLIR meters".

There is also a link on the same page to call their technical support.


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