How to check flame rod with cheap meter

This one compares a very cheap meter with a good one when used to test microamps on the gas furnace flame rod. The cheap meter is not recommended for professional use but can be used by a homeowner or someone who does not commonly work on gas furnaces.
This video is part of the heating and cooling series of training videos made to accompany my websites: and to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

24 Replies to “How to check flame rod with cheap meter”

  1. Hi, I have lennox g61mpv giving low flame sense error. The rod is clean. I am getting 3microamp going into the rod. But no microamp on the ground side going back to the board. When I disconnect this ground wire from burner box the error goes away BUT why is the furnace still running fine? Thanks

  2. Man is right about leads!!!!! Years ago I started out with an Amprobe FS3 It had crappy lead to meter connections and almost got me killed! Had Fluke, Simpson, Triplett… My all time fav is the Amprobe AMP-330.

  3. Hello sir
    Please i would like to know what means ua low ck frod i a gas burner
    It keeps turning of and also the mesage sometimes says lockout no flame
    I appreciate your response sir

  4. Thanks. Learned what I needed to know. Started the season with a Mud Dropper Wasp blocking my 2'' fresh air intake. Now I'm having trouble with the flame sensor. My Trane circa 2005 would not work with a exact replacement. I use one for a Goodman Furnace which I had to bend every witch way and it was working since 2008. Now I put the old new Trane sensor in and it's working. Back then I didn't know how to check them. I had to put a new board in 2008. I had to purchase one to use immediately and got a warranty new board back instead of a refund for the one they made me buy so I have a spare. I also have a spare ignitor to have on hand. Miss the thermocouple simple furnaces of the old days.

  5. Thanks…if you remove the rubber hose going to pressure switch area on the furnace…while furn is running….what would happen?…

  6. Thanks i did that and got fluctuating .values 2-4ma…also i poked a drill in the pressure sensor hole and the burner stayed on today…so not sure if its flanecsensor or its the pressure switch opening…..with crud in it

  7. Where are you actually connecting the red and black leads on the flame trying to troubleshoot if bad flame sensor…..inhave a weather king gas fuenace that burners fire up,and then shut off after 1-5 seconds and then the fan comes on….

  8. the other thing is you need to know what an acceptable reading is. The controller should have this data on it, but not always…

  9. you DID mention it, but I see too many make the mistake of leaving the meter in AC rather than DC…. This must be noted to pay attention to a DC setting. Otherwise you get bad data, and start chasing ghosts…

  10. Have you tried the Fluke meter on AC and measured the current? It would be interesting to see that. BTW: Harbor Freight for the win 😉

  11. Always crystal clear instruction…I especially like the explanation of the meter setting for checking the flame rod…Some videos, showing this same type instruction don't….I have instructed before, students end up with meters like this last one shown, because it's all they can afford at the time…This man is my idol, with his easy to understand terms, not talking over some ones head or making a person feel in anyway, inadequate or stupid…Thanks Furnace man.

  12. Nice video, thanks. I'm honestly pretty impressed that a cheap meter like that can accurately measure such small currents.

  13. El cheapo meter just as accurate as the fluke…..bwahaha…..go cheap my friends I had one I used for 5 years

  14. Hey I haven't ex11c Rinnai wall heater and it's pulling a cold 11.
    Could you show me how to test the burners or clean them, I'm in Maine and it's getting cold I've got the fireplace but I really need that propane heater working, thank you.

  15. Ok, I had to replace my pressure switch – was sticking open. Now the furnace lights, but only for a few seconds, shuts off and tries again. Cleaned the flame sensor – didn't work. Replaced the flame sensor – didn't work. I checked the wire from the sensor to the ECM(?) with my cheapo multi-meter. I had resistance (~.5 ohms) so I think the wiring is OK, but tested microAmps per this video and no reading (00.0 µA). I doubt the new sensor and the cleaned sensor are both bad… what do I do now?

  16. I thought the board was suppose to send 90 volts AC to flame rod then send micro amps DC back to board thru ground wire?

  17. The Harbor Freight digital meter may be "cheap," in price and construction but it has served me exceedingly well as a "non-professional" user where the measurement parameters really matter. Also thanks for this excellent video presentation.

  18. I work in vending. I acquired one of those meters via a birthday and while it did all it was required to after being dropped several times it ceased to function. Light duty only. I still use my old

  19. After sanding my flame sensor rod, the heater started working again. Just when I started jumping around like a nut and bragging to my wife that I fixed it, I noticed that the blower and inducer motor stayed ON a full hour after the heater reached the set temperature. After spending the day looking at many Youtube videos (including several of yours) and testing some of the other parts, I found what I believe to be the problem. I used an emery paper to sand that flame sensor rod… and I sanded it a LOT. I got a "continuous flashing" code that indicates "that a flame was sensed when there was NOT a call for heat" It said that code was generally used for a slow closing gas valve that has gone bad. BUT after thinking about it, I realized that code was perfect for my situation since the damaged sensor rod is also sending a message that "there is a flame when there was no call for heat".

    I plan on checking my flame sensor with my free Harbour Freight meter hopefully today, and was wondering what kind of reading should I expect to get ASSUMING that I damaged the rod when sanding it? Would you think that it would be higher or lower than 2.8?

    Thank you so much for sharing your wealth of knowledge and experience with us. Much appreciated here.on YouTube.

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