Volvo Penta MD2020 - RPM display stopped working

[alexincornwall]

Hi All,

A little advice/possible diagnosis required please:

Today I was performing a few mid season maintenance tasks including a little engine once over - impeller, oil, coolant inspection etc. Ran the engine for a few minutes and all fine (including cockpit RPM display). Finished off with a good deck scrub and a thorough hose down.

Returned to the boat a few hours later, fired up the engine and the RPM display appears to have stopped functioning. It was absolutely fine in the AM, so I'm assuming the hose down must have caused waster ingress. The Volvo unit itself is still functioning (glow, ignition, warning lights etc.), but the RPM needle lifts upon ignition and then drops off again.

Any immediate thoughts on that?

For the avoidance of doubt, the tachometer doesn't work, but hasn't done for a couple of years and I can live without that (common fault I've heard). I'd definitely like to know my engine revs though!

 

[VicS]

Hi All,

A little advice/possible diagnosis required please:

Today I was performing a few mid season maintenance tasks including a little engine once over - impeller, oil, coolant inspection etc. Ran the engine for a few minutes and all fine (including cockpit RPM display). Finished off with a good deck scrub and a thorough hose down.

Returned to the boat a few hours later, fired up the engine and the RPM display appears to have stopped functioning. It was absolutely fine in the AM, so I'm assuming the hose down must have caused waster ingress. The Volvo unit itself is still functioning (glow, ignition, warning lights etc.), but the RPM needle lifts upon ignition and then drops off again.

Any immediate thoughts on that?

For the avoidance of doubt, the tachometer doesn't work, but hasn't done for a couple of years and I can live without that (common fault I've heard). I'd definitely like to know my engine revs though!

RPM is displayed by the tachometer . I guess its the hour counter that has not worked for several years, as is usual

The first thing I would check is that there is power getting to the tacho....... the flick of the pointer when you switch on suggests that there probably is.

Then check the wiring from the tacho to the W terminal of the alternator ( Grey wire) ... that's where the problem probably lies

 

[Pavalijo]

My Volvo tachometer started flickering, then flickering with the reading falling, before eventually it mostly didn't work at all.
I took it home for the winter and left it by a radiator - and this year it has worked perfectly so far.

Strangely enough the hour meter, that had not worked for the previous 3 years (since purchase), sprang into life at the same time the intermittent fault began.

So - before spending hard earned pounds try the radiator treatment. Good luck,
Paul

 

[alexincornwall]

Thank you both for your helpful replies. I'll check the wiring at the alternator end but do suspect that their must be moisture in the unit somewhere along the lines - will try the radiator trick also.

 

[daverebbettes]

Hi, Did you sort this? I had the same problem and the problem was the exciter lead from my alternator. You will most likely find that you are not charging your batteries either. Let me know if you need any more info.

 

[alexincornwall]

Apologies, I had meant to update but was pre-occupied with a Scillies trip. The tacho was indeed dead and was replaced at a cost of around £300. The engineer reckoned water ingress was the issue. However the alternator was checked and found to be behaving erratically. I can't recall the exact symptoms but I belief it was sending power spikes to the electrical system. The batteries were charging, but not particularly efficiently.

All appears to be well now!

 

[twilliams_34]

Hi
Not sure if you kept your old unit but if you have I would be interested, will help to cover some of your costs ��
I am after a replacement screen for mine.

Tony

 

[alexincornwall]

Sorry Tony, I think the engineer must have nabbed it. In any case the screen was cracked.

 

[humphrey231074]

I removed a tacho on my volvo penta diesel engine that was fluctuating badly and had it checked by an electronics friend and he said there was not much he could do with it without damaging the circuit board further, so I bought a new tacho and all has been good. The hour meter on the other boats volvo tacho failed recently and I bought a new LCD screen also from the yachtboatparts com guys in Southampton and all the original hours came back as the hours information is retained in the tacho electronics not in the screen itself and took about 20mins to replace.