Tachometer

[tommyt]

I did a search and did not find this problem.

I own a 2004 C34. I am operating on my second tach after replacing the first 2 years ago.

The tach works fine just after the engine is started. It works for 15-45 seconds , spikes, and stops.

Any thoughts?

Tom

[Ron Hill]

Tom : Check your connections on the back of the alternator.  If all is OK and tight, then I'd give Teleflex a call (914)907-1000 and ask them your question.  
I'd definitely mention that this is my 2nd Tach.  Hope this helps  

[Lance Jones]

I don't know if it is the same problem. However, I had something similar that was causing fluctuations and then drop in RPM in the gauge. I finally adjusted the alternator belt and that SOLVED the problem.

[Stu Jackson]

1.  Check what Lance said.

2.  Check your connections at the back of the alternator, check your connections at the tach, check all electrical connections - if it's intermittent electrically, it is usually a connection.

3.  If you leave your dock with full batteries, sometime the regulator doesn't instruct the alternator to output.  No output, no tach reading.  Simple as that.

[tommyt]

OK, found part of the problem. They were checking the tach with shore power and charger on. Tach works fine without charger on. However, I thought that there was a diode that only allowed one to charge at the same time.

The hour meter however is not moving and I have tightened all wiring. Any thoughts on that?

[Stu Jackson]

1.   They were checking the tach with shore power and charger on. Tach works fine without charger on.

2.  However, I thought that there was a diode that only allowed one to charge at the same time.

3.  The hour meter however is not moving and I have tightened all wiring. Any thoughts on that?

1.  Thought that'd happen, always does.

2.  The diodes are INSIDE the alternator to make DC out of AC, has nothing to do with the exterior circuit.  Diodes are electrical check valves, they allow allow current to flow in one direction.  They will blow in the alternator if the alternator output is interrupted, which is why we keep telling people to get their AOs OFF the 1-2-B switch and directly to the house bank.

3.  Hour meter only works when the key is on.  Tightening wires at the back of the hour meter is only one part of the solution.  Get a digital voltmeter and find out if there's power there.  If not, keep tracing and find out why.  Make sure the 1-2-B is ON and the key.  Obvious I know, but you know how I know, right?  Is an electrical parallel of "My engine won't start!" 'cuz I forgot to push the kill handle down when I fueled up!

Tommy, please let us know more about you so we can help even better:  See Identification, here: http://c34.org/bbs/index.php/topic,1506.0.html

[tommyt]

Talke to one of the best diesel and marine mechanics in the area today. He said if the tach is working and the hour meter is not, replace the tach. One drives the other and the drive mechanism is shot.

Cheaper to replace than play with anyway I guess.

[Stu Jackson]

Tom,

Thanks for adding your signature information.

I agree about replacing the instrument if one of the two parts isn't working.  Maybe, maybe not though about how it works.

I think you'll find that if you have your key switch ON and the engine is NOT running (i.e., alternator not working, tach not running) that your hour meter will still be going around and adding hours, because there is power to it.

There are four connections to the tach instrument.  http://www.c34.org/wiki/index.php?title=Image:Harness4.png  Black - ground, red - power from the ignition switch and to the hour meter; gray - tach signal from the alternator; (same) red to the light in the instrument.

I simply disagree with your mechanic.

Try it some time.  That's been my experience.

[Ron Hill]

Tom : I just don't think it's a good idea to have shore power / battery charger ON and start then the engine at the same time. 
I know what diodes are supposed to do - I just don't like competing charging systems ON at the same time !   My thought

[Mike and Joanne Stimmler]

I think you'll find that if you have your key switch ON and the engine is NOT running (i.e., alternator not working, tach not running) that your hour meter will still be going around and adding hours, because there is power to it.

Stu, I never tried leaving the key on without the engine running but when I replaced my tach because the hour meter quit working, I could not get the hour meter to work on the bench by just connecting 12v to it and I thought I had another bad unit but when I installed it with the tach wiring connected, it all worked just fine.
So it seems to be reliant on the tach being connected, but I'm not sure if the engine has to be running or not.

Mike

[Ed Shankle]

Tom,
I too have had a problem with my hours meter not working. Thinking that the mechanism might be just stuck, I tried tapping it firmly to free it. It did, but I noticed it always stopped on the "9". That confirmed there was something with the mechanism. So whenever it reached nine and stopped, I'd give it a rap. Eventually it seemed to free up and only stops once and a while now. Give it a try!

Ed