I purchased an Ohmite potentiometer off
eBay hoping I could check the gauges in
my ’69 Charger. The ad said it was a 250
Ohm / 50W Rheostat unit. When I put my
digital multimeter on it, I see resistance
from about 5 to 115 ohms. I’m not sure
that matters as long as I can adjust it
between 10 and 73 ohms which I can.
My dilemma is I don’t know how to
connect everything between the gauges
and the potentiometer to check them.
I’m also not sure what to use as a power
source and how to run the wires through
the 5V regulator.
I’m hoping you can help me with a
quick diagram so I can check the gauges
without damaging them. I did accomplish
a quick check with two AA batteries and
the needles moved so I know they’re
functional (two of them were not working
in the vehicle).

Sure, see above. The gauges can still
be in the cluster, or not. The polarity of
the gauge connections is also unimportant—
they are thermal devices, like a light
bulb or electric heater. Plug your 100-watt
incandescent bulb reading lamp in either
way, it matters not one whit.
Instead of buying the potentiometer
(this could also be a rheostat, the 2nd
“end” connection is unused), you could
also just get one 10Ω and one 75Ω wirewound
resistor, 10 watts or better. A
potentiometer sure looks cooler though—
like some Dr. Frankenstein lab piece.
Remember, each gauge has individual
hi and low adjustments.

Testing gauges is easy, in or out of the cluster. See text for details.
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