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Old 07 July 2009, 11:35   #1
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Bombardier tacho fault

The tacho on our boat has recently packed up.
The needle has been a little 'sticky' for a while - you sometimes had to tap it to get it to drop back down from higher revs - but now there's no movement of the needle at all. The engine warning lights are also in the tacho and they all seem to be working OK.
The terminals in the block connector on the back of the instrument are clean and bright so I don't think it's a bad connection there.
Does anyone know if these work in the same way as automotive tachos, i.e. there's a pulsed signal from the ECU that increases in frequency as the revs rise. If so, does anyone have a wiring diagram so I can check if the fault is in the tacho (v. likely given the history) or in the cable/at the engine?

The controls/instruments are Bombardier, running off a 2005 Johnson 140 4 stroke.

Thanks.
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Old 07 July 2009, 13:34   #2
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Most likely in the tacho.
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Old 08 July 2009, 09:10   #3
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I agree with you Jiz, but it would be nice to double check if poss before shelling out for a repair/replacement.
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Old 08 July 2009, 09:34   #4
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I agree with you Jiz, but it would be nice to double check if poss before shelling out for a repair/replacement.
my understanding is that until very recently all outboard tachos worked by measuring the frequency of an a.c. signal that comes from the alternator/flywheel. Some more modern hi-tech ones may be artificially generated signals from some electicarry in the engine. On my (completely different brand of) engine you can measure the a.c. voltage going into the "signal/ground" wires on the tacho and see it rising as the revs go up - its completely uncalibrated - but would confirm that the wiring is OK. If you have a fancier multimeter you can probably measure the frequency of the pulses.
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Old 08 July 2009, 11:12   #5
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After doing a bit of searching, it looks like OMC/Bombardier use a 3 wire system (+12V, 0V, signal) which is reasonably universal so it should be possible to test the signal from the ECU.
I've got the tacho off the boat now, and I'm fairly sure it's FUBAR but I might hook it up to a signal gen to make sure. It's probably going to be easier than dragging the boat out of the garage and running out the hose so that I can run the motor up on the mufflers.
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Old 08 July 2009, 13:17   #6
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Yes, try to get hold of an analogue meter to check the signal, it will be alot easier to see.
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Old 20 July 2009, 04:44   #7
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Originally Posted by Dry_Doc View Post
The tacho on our boat has recently packed up.
The needle has been a little 'sticky' for a while - you sometimes had to tap it to get it to drop back down from higher revs - but now there's no movement of the needle at all. The engine warning lights are also in the tacho and they all seem to be working OK.
The terminals in the block connector on the back of the instrument are clean and bright so I don't think it's a bad connection there.
Does anyone know if these work in the same way as automotive tachos, i.e. there's a pulsed signal from the ECU that increases in frequency as the revs rise. If so, does anyone have a wiring diagram so I can check if the fault is in the tacho (v. likely given the history) or in the cable/at the engine?

The controls/instruments are Bombardier, running off a 2005 Johnson 140 4 stroke.

Thanks.
Did you get to the bottom of this I have the same problem.
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Old 21 July 2009, 11:22   #8
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Did you get to the bottom of this I have the same problem.
I think so, but I've not had the boat out on the water since it's been repaired to check if it's properly fixed.
It seems like it was a physical fault with the needle binding on the dial face where the shaft passes through. I had to strip the glass/bezel assembly from the unit (it's crimped on so you have to carefully lever the metal bezel all the way around until it's free enough to get the assembly off the body) and then reseat/realign the face which is held in position by a plastic spacer.
Once back together (recrimping is a delicate job with a small hammer!) I connected it to a signal generator and it seemed to work fine. Back on the boat it also seems to be fine but I don't want to rev it when it's only running on the mufflers!

I'll let you know if it's properly fixed after next Friday.
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Old 23 July 2009, 06:01   #9
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Something is a miss in my electrics, allthough ive had the boat in pieces, with! Rev counter doesnt work, Trim guage doesnt work and now the fuel guage! My stereo, light pole, gps etc all works fine... Dont know where to go with it now..
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Old 23 July 2009, 06:38   #10
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Something is a miss in my electrics, allthough ive had the boat in pieces, with! Rev counter doesnt work, Trim guage doesnt work and now the fuel guage! My stereo, light pole, gps etc all works fine... Dont know where to go with it now..

Have you got a multimeter? If so there's quite a few things you can check before seeking professional (expensive!) help. It will also help to have a long lead with a croc clip on each end if you have to test any cables for continuity.
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