Forum Discussion

landyacht318's avatar
landyacht318
Explorer
Dec 03, 2014

DMM thermocouple cant reach alternator.

My Sears clamp on Digital MultiMeter Model # 82369, came with a temperature probe.

It is too short to reach my alternator, unless I were to close dog house cover over it. I fear damaging it or getting incorrect readings by doing so, and driving with cover cracked open or off, Is not desirable.

I want to see temp readings, while driving, when the alternator is maxed out on a well depleted battery, with different levels of air moving underhood at different vehicle wpeeds.

Curiosity, nothing more, at this point. But a dedicated CAI might be a future project if temperatures prove alarming.

I hope to get a longer thermocouple/lead.

What do I need to know to begin the hunt for the product I seek?I'd say 5 foot minimum is needed to reach dashboard mounted DMM from alternator.

Are these fairly universal?

If I do get one, Where would be the best spot to attach the probe on the alternator. External case would be easiest, but will it be truly indicative of rectifier heat?

What temperature reading should I expect when maxed out?

14 Replies

  • You can add a basic copper wire extension, but the measured temperature will not be correct because the open circuit voltage at the thermocouple connection end must be held at a reference temperature which is maintained inside the meter.

    To get the correct reading you will need to extend the thermocouple wire types used for the "K" type couple.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    You can extend the leads if you must Just use clip on test leads (the kind with a clip on each end) I would tape or tube the junction.

    At the meter end use the probes, and again tape or tube the joints

    I noticed on mine the probe may be polarity senistive (is marked + and -) so pay attention the red lead is plus.

    Nice meter, There is one just like it beside me.

    Note: the temp probe may give false readings I think it is more accurate if you turn on the meter, quickly get a reading and turn it back off.
  • Ok it is a K type thermocouple. Shoulda did a bit more research before posting.



    Plenty of different length options.

    But if anybody wants to discuss probe location and what temps can be expected when maxed out, I'm game.

    Perhaps I'll continue this thread with results if there is interest, and if not, I'll hog all the Data and you'll get Nothing!!