Rev Counter doesnt work!!

Re: Rev Counter doesn\'t work!!

I think you will find that your tacho is dead. If I remember correctly you connected it incorrectly in the first place and the electronics inside is very unforgiving.

If I remember correctly, the front end of a tacho is possibly a Field Effect device (FET) and the sad thing is that they only cost abour 25p +VAT in the UK. If it is not a FET, then it will be another three-legged fuse inside.

If you can get it to any decent electronics engineer who has access to a signal/pulse generator and a 12volt DC supply, he should be able to test it for you fairly easily. Saves struggling about on your yacht.
 
Re: Rev Counter doesn\'t work!!

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The DC reading was perhaps a misnomer - I took it 'cause I could and, perhaps, it is a coincidence that it reads 7v DC, which is what was expected from the AC reading.

My concern is that the AC reading is 16V AC, rather than the 5V-7V suggested - i.e. more than double?


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It should be 7 volts DC, not AC. That being said, with what I have since read, I suspect the rev counter too.
 
Re: Rev Counter doesn\'t work!!

Its hard to see how the W output could be faulty if the alternator's charging normally and you're getting "something" not unreasonable from the W. Its just a direct connection to some part inside the alternator, not a separate set of electronics that good go awry.

Since its a normal W output, presumably the rev counter doesn't have to be a special Volvo part?
 
Re: Rev Counter doesn\'t work!!

An alternator has three separate phases. The W signal is taken from one of the three phases. I have seen many faulty alternators over the years, where a phase, or two are down. Obviously if it happens to be the phase that is connected to the W terminal, then there is no tacho signal.

You will still see the correct charging voltage with one, or even two phases down, as the remaining phase (s) will continue to work.

As for the rev counter, you are right, any 12V replacement would work with that signal.

Just to make it clear from my last post, as I can see it could be read two ways, my suspicion is that the alternator in this case is fine and that the fault lays with the tacho, especially if, as has been mentioned, it was connected with reversed polarity.
 
Re: Rev Counter doesn\'t work!!

"especially if, as has been mentioned, it was connected with reversed polarity."

The tacho/panel has only ever been disconnected once in my time. This was late last week, 18 months after the tacho failed, and I put everything back as I found it.

At the time the tacho failed, I had removed the sense wire, (yellow), from the alternator, and connected it to sense from the battery direct. Some people have suggested that it is pure coincidence that the failure of the tacho took place at the same time.

Anyway, I think we've diagnosed the problem, and covered a bit of ground in between.

Now I need to find a tacho that fits the panel, or a new panel.

Many Thanks to all for the help.

Richard
 
Re: Rev Counter doesn\'t work!!

____________________________________________________

If you can get it to any decent electronics engineer who has access to a signal/pulse generator and a 12volt DC supply, he should be able to test it for you fairly easily. Saves struggling about on your yacht.

____________________________________________________

Morning Dave, there is no need to go to these lengths. If you make up a 7.5V battery, or even use a 9V like you find in smoke alarms, connect the tacho to its normal power supply then connect the neg of 7.5/9V to the neg of the tacho and pulse the positive to the signal input, either by flicking the terninal with the +ve wire or through a push button. You will see the needle of the tacho "jump" or "pulse" as you do this. Alan.
 
Re: Rev Counter doesn\'t work!!

I shouldn’t think you will have too much trouble finding one to fit, although if you use one from a petrol engined vehicle there will be some rather high numbers on it……! /forums/images/graemlins/grin.gif
 
Re: Rev Counter doesn\'t work!!

[ QUOTE ]
Before you buy a new tacho (you'll pay through the nose 'cos though it's made by VDO you can only get them from Volvo) get yourself a multimeter with a frequency measurement facility. You should get a clear reading across the tacho. connection.

[/ QUOTE ]

I'm going to try and get a multimeter with frequency measurement, before finally deciding that it is the rev counter that is duff.

In the meantime, I've got a price of £172, (ouch!!), for the rev counter from Keyparts. Apparently it's not the original, (VP 873688), but a generic replacement which needs setting for the engine.

Richard
 
Re: Rev Counter doesn\'t work!!

I've been thinking about a TinyTach since the problem occured, but not sure if I want to go to the trouble of drilling holes, and feeding wires along a tortuous route .... which would probably mean removing the rear heads headlining, (which is a major PIA!).

Also feel like it would still look like something wasnt working if the original counter wasnt working.

But I'm thinking about it /forums/images/graemlins/smile.gif

Many Thanks

Richard
 
Re: Rev Counter doesn\'t work!!

Richard
Im bidding on a panel for a VP now, im after the control box, the rev counter will be going begging, and if i dont win it, rob in harbour marine in pwllheli has got a spare panel with no controller with one in, hang fire!!
Stu
 
Re: Rev Counter doesn\'t work!!

I'm hanging fire!! Going home May 6th, and I dont need to do anything until just before I return to Malta at the end of May.

Harbour Marines panel might be just the ticket as mine is a bit tatty... presumably the controller can be swapped out?

Many Thanks

Richard
 
Re: Rev Counter doesn\'t work!!

Richard
Give Rob a bell, search on harbour marine pwwllheli, he is a good chap and not dear, am led to believe that the controllers are basically the same, also see this post with the wiring diag, courtesy Vics, http://www.ybw.com/forums/showflat.php?C...ID=#Post2276628 you can see the negative is joined internally so not rely necessary to have it on externally, also you can see where the 61 wire goes
Stu
 
Re: Rev Counter doesn\'t work!!

Hi Stu,

I'm asking if the controller can be swapped out without actually knowing which bit of the panel it is /forums/images/graemlins/smile.gif

Can you give me a clue?

I've got VicS wiring diagram in my manual, and it all seems to make sense.

The brown 61 disappears into the PCB area along with a bundle of other wires, so I can see why the external one isnt connected.

Cheers

Richard
 
Re: Rev Counter doesn\'t work!!

Richard
the controller is the rectangular bit with the bulbs in, 2 machine screws (brass) hold the thing to the board, its got the multiplugs coming from it.
Stu
 
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