Tach not reading on a 2007 SO42DS

[cabrillojim]

The tachometer quit reading RPMs while the engine key is in the "On" position, and the Engine low battery alarm sounded on the Nav Station control panel about 30 minutes after the tach stopped. The blower continues to function while the engine key is "on". The belts are tight, and all the connections on the voltage regulator are intact. Does the tach get the signal from the generator? Do these symptoms mean the generator needs replacement?

Also, the Engine start panel may need replacing. The engine start key does not properly indent to the Run position, and the engine hours display LCD is fading. Will the Yanmar dealer have a new key panel?

[Kai Rani]

You would probably better to get a new panel on line. You can replace the led engine hour piece ( google to find a supplier it’s a Volvo part )you do need to pull the tachometer assembly apart ( youtube) if you don’t have proper switching of the ignition this would affect the tachometer

[Mistroma]

Tacho gets a pulse from the alternator on my 42DS, check if that wire is disconnected. You can check the alternator output, voltage on panel increase when engine is running and get above 14V if batteries are nearly charged.

The tacho connects to a T-shaped plug in connector on the back of my Hitachi 80A alternator. See the connector with orange, red and blue wires in the picture below. You can also check that it is still connected at the rear of the tacho. Just a thought as an initial check.



I'm assuming your 42DS is older than my 2009 model as I only have start switches on the panel, no key.

[cabrillojim]

Jul 14, 2023 23:12:52 GMT Kai Rani said:

You would probably better to get a new panel on line. You can replace the led engine hour piece ( google to find a supplier it’s a Volvo part )you do need to pull the tachometer assembly apart ( youtube) if you don’t have proper switching of the ignition this would affect the tachometer

It is a Yanmar JH4 Series diesel

[cabrillojim]

Jul 15, 2023 10:53:25 GMT Mistroma said:

Tacho gets a pulse from the alternator on my 42DS, check if that wire is disconnected. You can check the alternator output, voltage on panel increase when engine is running and get above 14V if batteries are nearly charged.

The tacho connects to a T-shaped plug in connector on the back of my Hitachi 80A alternator. See the connector with orange, red and blue wires in the picture below. You can also check that it is still connected at the rear of the tacho. Just a thought as an initial check.



I'm assuming your 42DS is older than my 2009 model as I only have start switches on the panel, no key.

It is a Balmar Alternator on a 2008 42DS

[Mistroma]

I thought it might be the Hitachi 80A as that was standard on quite a few engines. I also have a spare Balmar alternator and it has a connection for the tacho.

The installation guide is on my website and diagrams show the position of the tacho connections for several models.

Open it find (Crtl-F) tacho and step through each occurence. I think you need to scroll back up for the first diagram but others are usually visible. The diagrams show where to find the connector for the tacho feed. I hope this helps and has information about the model you have on your boat.


www.mistroma.com/Manuals/BalmaInstallationGuide.pdf

[sitara]

Hi cabrillojim,

You seem to have raised several different issues if I have read your post correctly.

1. Tacho stopped reading: Check wiring especially terminals for corrosion or breaks as suggested  by others. behind the instrument panel and at the alternator.

2. Engine battery low alarm: Check that the alternator is producing sufficient voltage with a multimeter as suggested my mistroma

3. Engine start key: Maybe some lubrication will help here, or replace the lock system. The panel on my boat uses push buttons, no key.

4. Hour meter fading: This is a fault with these tachos, the engine hour display can be replaced for a few dollars, search for AKSpeedo (https://www.akspeedo.com/vdo-lcd-repair.php) and videos on replacing the part. It may appear daunting but it can be done (I did it) and it is way cheaper than replacing the whole instrument.

Hope this helps, Rob

[cabrillojim]

Thanks All