Volvo MD 22 Tacho not working

[TheBoatman]

Hi all
I have a Volvo MD 22 56hp engine with the standard instrument panel (engine is approx. 16 years old). On starting the tacho sits at zero for a few seconds and then immediately goes to full revs ~ any ideas on what might be wrong ~ how do I test it and try and make it work.

Thanks in advance.
TheBoatman.

 

[VicS]

Hi all
I have a Volvo MD 22 56hp engine with the standard instrument panel (engine is approx. 16 years old). On starting the tacho sits at zero for a few seconds and then immediately goes to full revs ~ any ideas on what might be wrong ~ how do I test it and try and make it work.

Thanks in advance.
TheBoatman.

Start by checking all the connections. Power supply to the instrument and more especially the grey signal input wire, its connection to the alternator W terminal and the intermediate connections in the wiring loom.

(refer to the wiring diagram in the owners manual)

 

[TheBoatman]

Thanks Vic.

TheBoatman.

 

[Monique]

I'm afraid this problem is a "no cost" option... had to replace the tach myself on previous boat. It seems the unit is not sealed correctly against water ingress and the inside goodies get a water treatment which is not intended.

I added a electrical tach on the engine itself powered through the key.

 

[charles_reed]

I'm afraid this problem is a "no cost" option... had to replace the tach myself on previous boat. It seems the unit is not sealed correctly against water ingress and the inside goodies get a water treatment which is not intended.

I added a electrical tach on the engine itself powered through the key.

May be the tachometer dying but in my experience (on 3 occasions) it was a preliminary signal that the alternator was about to fizzle out.
The only thing one really needs on an engine is an hour-meter and replacement tachometers being such silly money I'd do exactly as Monique has done - fit a key-connection counter.
Whichever it is correction is, sadly, expensive.

 

[MM5AHO]

I replaced my Volvo tachometer, but didn't use a Volvo replacement (which is actually some other brand).
I bought a low cost one on Ebay, and its done three seasons without problems so far.
It was a different diameter, so I made an adapter plate to fit it into the panel.