Rev counter stopped working

steved

steved

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Good day all

Volvo KAMD43 circa 1998, rev counter was working normally a week ago, now stopped showing any revs whatsoever.
The LCD hours display comes and goes depending on how it feels.

When the ignition is switched on there is a flicker of the rev counter needle, albeit downwards, and then nothing.

Any thing obvious that I should check?

Thanks
Steve
 
Not 100% sure but on my engines, the rev countre gets its data from the alternator, and when the belt started slipping, no revs. Mine are Cat engines so this might be a red herring.
 
Might be totally off track but the volvo rev/hour meter in our dash packed up, removed and stored in airing cupboard for a few days, has been fine ever since, damp was the main suspect.
 
rafiki_ said:
Not 100% sure but on my engines, the rev countre gets its data from the alternator, and when the belt started slipping, no revs. Mine are Cat engines so this might be a red herring.
Click to expand...

The engine was recently serviced, with a change of belts etc, however, the voltmeter was showing a good charge throughout which would probably indicate that the belt wasn't slipping. I will check the belt tension though.
 
First thing is to check all the connections to the back of the alternator, and if you can get at it the back of the tacho.

If it's concluded you can get them repaired by a company called speedy cables
 
Some VP's have sensors by the front pulley and some pick up from alternator, the fact the hourmeter is also playing up points to a faulty gauge.
The idea about taking home to dry is worth trying.
 
steved said:
Good day all

Volvo KAMD43 circa 1998, rev counter was working normally a week ago, now stopped showing any revs whatsoever.
The LCD hours display comes and goes depending on how it feels.

When the ignition is switched on there is a flicker of the rev counter needle, albeit downwards, and then nothing.

Any thing obvious that I should check?

Thanks
Steve
Click to expand...

The Volvo Penta KA(M)D 43 takes it's tachometer signal from the 'W' terminal on the alternator. Damp in the instrument is the usual culprit for these failing, but I would not advise checking tachometer connections, as if it was working ok before these rarely fail. Secondary source of problem is damp/water getting onto the alternator causing a build up of corrosion to prevent the signal output. This can be tested by a multimeter set to VAC output, you are looking for approx. 3VAC when running. The volts should not change with rpm, it is the frequency of the signal which changes so this can be tested at idle speed.
First check which is fairly hassle-free (depending on your helm layout) is to remove the tacho and store in the airing cupboard for a few days to dry out and then refit and test.
Good luck
 
Hi,

The KA(M)D, as all the mechanical KA(M)D series engines take the tachometer signal from the 'W' terminal on the alternator. Two common problems are: 1-damp in the gauge and; 2-damp/corrosion in the alternator. The instrument can be removed and dried in the airing cupboard for a few days as suggested earlier, the alternator can be tested by measuring the output at the W terminal with a multimeter set to VAC. You should see 3vAC at the alternator, the volts will stay the same regardless of rpm, it is the signal frequency which drives the tacho. Sometimes, especially after these have been left over damp months some moisture can get into the alternator and corrosion can build up on the contacts. If this is common, you may also have to give the engine a 'rev' to get the alternator to excite to turn out the charge warning light.
Good luck
 
GAMPortsmouth said:
The Volvo Penta KA(M)D 43 takes it's tachometer signal from the 'W' terminal on the alternator. Damp in the instrument is the usual culprit for these failing, but I would not advise checking tachometer connections, as if it was working ok before these rarely fail. Secondary source of problem is damp/water getting onto the alternator causing a build up of corrosion to prevent the signal output. This can be tested by a multimeter set to VAC output, you are looking for approx. 3VAC when running. The volts should not change with rpm, it is the frequency of the signal which changes so this can be tested at idle speed.
First check which is fairly hassle-free (depending on your helm layout) is to remove the tacho and store in the airing cupboard for a few days to dry out and then refit and test.
Good luck
Click to expand...

Thanks for the advice, I'll certainly check the voltage from the alternator first and advise outcome.

Fortunately the tacho is easy to access and remove and I will do this if the volts are ok.
 
I have tested the VAC output from the W terminal and it was showing 3V, also the reading from the terminal at the rev counter end was showing 3V.

Tachometer head had been in the airing cupboard for a few days, and when I reinstalled the unit on the boat and started the engine the LCD was reading 'code', but no movement on the rev counter. The LCD display flickered for a bit then went blank.

I presume the tacho unit is knackered for what ever reason, can they be repaired or do I have to source a replacement?

(VPn. 873660 refers)

Thanks
 
After further checks it was determined that the VP tacho was knackered, strange the way some things work one week then for no apparant reason stop working the following week......

Didn't want to pay VP prices for a replacement, so my electrics man fitted a WEMA tachometer, and as the boat is single engined it doesnt look out of place at all. The only downside is the hour meter is now reading zero, but at least it works!

I had previously fitted an analogue hour meter with the correct engine hours (after having it connected to a battery for 24 days to get to the correct number of hours!) so the hours issue should be explainable as and when the boat is sold.

Thanks for the various advice.
 
If the taco was coming up code then you need to code it, simple job , just find out which impulse code is req and set it up.

I can't source the correct code setting at the moment as books are in the van but it sounds like it just requires a code so it can read the signal from the alternator. Maybe that was the problem at the start , but as the display wasn't working and now is after it's drying out session you can see it was asking you to code it.
Don't throw it away as there over £300 new.
 
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