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Yamaha Multi-Function Display (Tach) Not Reading

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Yamaha Multi-Function Display (Tach) Not Reading

Old 07-08-2013, 05:27 PM
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Default Yamaha Multi-Function Display (Tach) Not Reading

I have an '02 150 hpdi. The tach does not show anything when the motor is turned on or running. I assumed the tach was dead or had a loose connection until I ran the boat at night for the first time. The tach was back-lit just like the speedometer so now i'm wondering if there could be something else causing the malfunction other than the tach itself.

How do I trouble shoot this thing to make sure I don't unnecessarily replace the display

Any ideas?

Thanks!!
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Old 07-08-2013, 05:49 PM
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The backlight is powered by the blue wire. The the tach gets power from red and ground black so you can check those with a voltmeter. If wires checkout, borrow a gauge and test it.
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Old 07-08-2013, 07:00 PM
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Actually the tachometer gets its power from a yellow wire. Yellow being the wire colour that Yam uses for key on power. Should be four single wires going to the tachometer. Yellow, black, green and blue.

The back light (blue wire) may be getting its power from a switch or some other circuit separate from the power for the tachometer. There is a small harness that runs from the key switch to the tachometer. Check the fuse in that harness.
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Old 07-08-2013, 07:32 PM
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The same thing has happened to me twice over the years on my '94 gauge. Both times it was a blown 10 amp fuse. I believe there are two of the glass cartridge type fuses that feed it and they are inside a rubber jacket. You should be able to tell by looking at it if the fuse element is blown, or you can use an ohmmeter. The well under my gauges doesn't drain well and water collects in there, which could be your problem too.
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Old 07-09-2013, 08:26 AM
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I found and checked both fuses(yellow and red) and they are both good. The yellow wire(power) runs to a splitter that both the Tach and the Speedo are plugged into. The speedo has power so I'm guessing the Tach does too(don't have my meter).

The 4 single wires that run to the Tach are Yellow, Blue, Green and Black as you said. I only found a fuse on the yellow. The other fuse was on the red which only runs to the speedo. The green wire only runs to the Tach but I don't see a fuse on this wire anywhere.

Also, I noticed a rubber plug on the back so I pulled it out. There is a small switch under there with 3 toggles on it. #1 is up, #2 is down, and #3 is down. Could this have anything to do with my problem?

Thanks again for any help, I am a nuts/bolts type person, i struggle with electrical issues.....

Last edited by 10knotsorless; 07-09-2013 at 08:52 AM.
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Old 07-09-2013, 09:20 AM
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Try temporarily plugging the tachometer into the red wire and the speedometer into the yellow wire and see what happens.

The green wire does not have a fuse.
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Old 07-09-2013, 09:36 AM
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Ok, just tried that.

No change, speedometer display came on as normal, Tach stayed blank.
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Old 07-09-2013, 09:41 AM
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Originally Posted by 10knotsorless View Post
.

Also, I noticed a rubber plug on the back so I pulled it out. There is a small switch under there with 3 toggles on it. #1 is up, #2 is down, and #3 is down. Could this have anything to do with my problem?

.
Just installed a new Tach. These dip switchs are to setup the tach. 2/4 stroke, 6/12 pole generator, 2/3 wire trim sensor,,, if your tach was working,, these should be OK


Yellow - ign power
Blue - Lights (nav)
Green - Tach signal
Black - ground

Is the oil level and trim display working???

Last edited by gtpvettte; 07-09-2013 at 09:53 AM.
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Old 07-09-2013, 10:02 AM
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Originally Posted by gtpvettte View Post
Just installed a new Tach. These dip switchs are to setup the tach. 2/4 stroke, 6/12 pole generator, 2/3 wire trim sensor,,, if your tach was working,, these should be OK


Yellow - ign power
Blue - Lights (nav)
Green - Tach signal
Black - ground

Is the oil level and trim display working???

The tack is completely blank, Oil Level, Trim and all. The tach has not worked since the boat was purchased in February. The only part of the tach that works at all is the backlight.

The motor is original to the boat so i assume the dip switches are still in the factory positions.
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Old 07-09-2013, 10:06 AM
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Originally Posted by 10knotsorless View Post
The tack is completely blank, Oil Level, Trim and all. The tach has not worked since the boat was purchased in February. The only part of the tach that works at all is the backlight.

The motor is original to the boat so i assume the dip switches are still in the factory positions.
Sounds like no ignition power,,, or it's toast and time for a new one. There are two other harnesses going into it for the oil and trim correct?? If you need a new one,,, contact Andy at Sim,, they've got them.
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Old 07-09-2013, 11:10 AM
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If the ground is known to be good, and 12 volt power is being applied to the yellow wire, but the tachometer does not light up, I would surmise that the tachometer is dead.

I am thinking from the past here and seem to remember some Yam tachometers having two black wires. One for the lamp and one for the tachometer itself. If your tachometer has two black wires then both need to be connected to ground.
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Old 07-09-2013, 11:58 AM
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Originally Posted by jethro1 View Post
If the ground is known to be good, and 12 volt power is being applied to the yellow wire, but the tachometer does not light up, I would surmise that the tachometer is dead.

I am thinking from the past here and seem to remember some Yam tachometers having two black wires. One for the lamp and one for the tachometer itself. If your tachometer has two black wires then both need to be connected to ground.
That is the same conclusion I am coming to.

The ground must be good because it is shared by the Speedo. Also, the yellow wire powered the Speedo fine so it must be getting full power. I will double check everything once I get my meter but I'm fairly certain I need a new tach.

Next question, where is the best place to get one??

Thanks for all your help guys!!
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