1989 GL1500 tachometer died.

[YaBoyJB]

Hi all! My tachometer quit mid ride the other day I checked the wires with a circuit tester. Everything is doing what it should. When I check the red and black wires leading from the board to the needle mechanism they both show the same circuit. Is this an issue shouldn't the black wire be a ground? None of my capacitors appear to be blown or bad so I'm at a loss.

[wingdings]

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[brettchallenger]

Yep, mine died the other week too. So if you can find a way of fixing it, without having to remove the entire dashboard and sending the tachometer off to a specialist, I would be interested to hear from you. Thankfully, it doesn't stop me riding, I rarely look at the gauge but it annoys me it is dead.

[DenverWinger]

The Tach gets its signal from the ECM, tied internally to the spark output for one of the coils. If you have a loss of engine power -only running on 4 cylinders- it's a good bet one of the coil outputs of the ECM has failed. These are repairable, BTW.

If the engine is running normally, check the tach output of the ECM - yellow/blue wire on pin 19. This has a pulsing DC output corresponding to the ignition trigger to one of the coils. Best way to check this is with an oscilloscope. But if you don't have one you can use an AC Volt meter.

With your voltmeter set to AC volts, first measure the volts at your battery. It should briefly indicate some voltage and then settle near zero volts. Some analog meters will not do this and give a False AC volts reading on a DC input. If your meter does this then find another meter.

With the meter set to AC Volts measure the tach output at ECM Pin 19 with engine running. If no AC volts found (I'd guesstimate you'd see at least 2 volts AC, likely higher, depends on the pulse width of the signal) the ECM is likely the problem. If you do get an AC volts reading here, the problem is most likely the tachometer itself, or a connection fault. The Tachometer output from the ECM passes thru connectors C72 and C66 on a yellow/blue wire to get to the Tach.

EDIT - This information was based on the wiring diagram for a '94, should be applicable for 1990-2000 model years. Someone will need to provide the correct info for a '89 model regarding ECM pins, wire colors and connectors, but the test will be the same.

[brettchallenger]

Thanks a lot for this. This will give me something positive to do during this stupid lockdown we have, though I might wait a couple of weeks so my brother (who is a physicist) can come to my garage legally, and we will do it together. I have a decent multimeter so should be able to manage. I suspect the problem to be electrical rather than the meter itself, as it just suddenly went from working faultessly, to not working at all.