I had a go at the testing the 'gauge today with a VOM, not totally successfully. [failed to get amp readings properly.]
With the negative 12V battery cable removed, and the volt/ohm meter connecting to ground:
without gauge: 12.72V;
connected was 12.47V
Battery post to post was 12.98V just following a series of short trips.
THE PCB connector at J1, pin 1 to pin5 read 12.78V on the VOM.
Battery is rated 420 CCA
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fwiw: I typically see 12.3V or 12.4V on the OBDIIC&C& 'gauge in mornings just prior to turning over the engine. That would be perhaps 14hrs after driving the day before, for normally about an hour.
It was difficult to locate
R20 as mentioned prior above to test for heat; possibly it's located underneath the black plastic material that keeps the cable secured; none-the-less, nothing felt 'hot' to the touch on the board.
Not sure if I was doing it right when attempting checking Amps with the VOM, but I couldn't detect amps at J1, pin1 to pin5 no matter what setting on the VOM dial while able to read dc V ok.
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After measuring the voltages with the newest chip in place, [which was repeated a few times in succession involving a series of quick removals and replacements of the negative battery cable], the parameter display error at the 'gauges third OBD position cropped up yet again.
This time some hex program code on the chip appears likely had become corrupted at a guess, as the elimination of the 3rd right side line following all the intermittent power interruptions on-off seemed to be permanent. The rest of the parameters were alright.
Whatever the case, refreshing the default 'def' selection in the config screen was to no avail. Looked at the Code ## and all was in order. ie. INJ=09.
Unplugged and replugged the device at the OBD; turned off ignition several times again, same result with the third OBD position parameter apparently gone.
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I next took the 'gauges case apart next and swapped out the new 18F' chip back to the earlier 16F' chip again.
Somewhat surprisingly, though it had happened previously, similar errors in the name section of the third OBD parameter were present with the first two letters missing. Keying off and on in this case rectified the default display.
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I'll try returning the newer chip back again in the board later after noting some voltages in the mornings with the earlier chip in place and measure the battery voltages with the VOM and try for some more measurements
I'll also grab an appropriately sized wire or paperclip to probe the OBD connection for better comparison. [And try and figure out if the amp meter is working on my VOM!]