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Old August 11th, 2017, 01:28 PM   #21
DannoXYZ
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Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011

Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C

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MOTY - 2018, MOTM - Nov '17
Quote:
Originally Posted by gitter View Post
Ok here's what I have so far:

1. with key ON, test for power at harness-side connector brown/black wire
12.6V

2. with key ON, test for power at gauge-side connector brown wire
12.3V

3. measure resistance between chassis-ground and harness-side connector black/yellow wire
.2

4. measure resistance between chassis-ground and gauge-side connector black/yellow wire
.3
This is good, means we're getting power to the gauges across the connector. They also have good grounds to chassis

Quote:
Originally Posted by gitter View Post
unplug ECU connector

5. measure resistance between ECU-connector black wire and harness-side connector black wire
.3

6. measure resistance between ECU-connector black wire and guage-side connector black wire
.3

7. measure resistance between ECU-connector black wire and chassis-ground
3.7
Good that black signal wire is intact to tach. NOT GOOD that it's shorted to ground somewhere between ECU-connector and coil/tach.

I guess you'll have to unwrap the loom starting at the ECU-connector and work your way forwards inspecting black coil wire along the way. At some point, it's frayed with a bare-spot and connecting to ground. Or where it splits off to tach may be shorted as well. Hmmm, maybe a short inside the tach?

Try this final test before unwrapping:

8. disconnect black signal-wire from coil
9. unplug gauge-connector from harness connectors
10. measure resistance of black-wire between ECU-connector and coil spade-connector
11. measure resistance of either end of black signal-wire to chassis-ground

If it has infinite-resistance (open), then we know there's short between tach and gauge-connector.
Otherwise, there's still short along way from ECU to coil, and we'll need to open up loom and inspect entire length of that black wire.

You can use the 'noid-light to test signal as well. Start at ECU-connector's green coil-wire as control to confirm light works. Then switch to black-wire terminal and verify ECU's sending out correct grounding signal (use any +12v for other terminal of 'noid-light). Then work your way up black wire and see where signal stops.
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