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Post by tonyb on Apr 24, 2021 8:15:12 GMT
Could it be getting a signal of something else like a short somewhere. @gazza advice of testing continuity between the alternator and counter is definitely something that should be done too. Partly because that's the feature on mine that I use the mostπ
I can't think of anything else that produces pulses on a typical boat system apart from the thermal instruments found on some old boats. In any case it would be a partial loss of pulses in the wiring rather than adding pulses.
I suppose if the full charging voltage was superimposed on the W cable it would swamp the pulses so the counter did not see them but it seems to me to be a bit unlikely for such a fault to only affect the rev counter.
If something was reducing the voltage of the pulses then the counter would either count them or not so the sticking at 700 seems odd.
Check simple and easier to get at things first and if they are OK I agree the pulses at the counter itself need checking but not as the first test. it it turns out to be a loose connection at the alternator then no need to go any further.
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Post by Deleted on Apr 24, 2021 8:18:05 GMT
I'll be looking into this later today, and will report back. Thanks for all the advice so far.
This mornings job being setting up a new (well old refurbished) laptop. Ex-current one = no bootable device when switched on this morning - grrrr.
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Post by Deleted on Apr 24, 2021 8:19:08 GMT
My rev counter defaults to 700rpm with the ign off I can't remember if it drops to O with ign on but works fine. Could it be losing 12v after starting thus causing the default of 700rpm?
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Post by Jim on Apr 24, 2021 8:59:47 GMT
I'll be looking into this later today, and will report back. Thanks for all the advice so far.
This mornings job being setting up a new (well old refurbished) laptop. Ex-current one = no bootable device when switched on this morning - grrrr.
Take the drive out and put it in an enclosure, then get all your old files off before wiping clean and having a spare hard drive. You may already know this.
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Post by Deleted on Apr 24, 2021 9:08:02 GMT
I'll be looking into this later today, and will report back. Thanks for all the advice so far.
This mornings job being setting up a new (well old refurbished) laptop. Ex-current one = no bootable device when switched on this morning - grrrr.
Take the drive out and put it in an enclosure, then get all your old files off before wiping clean and having a spare hard drive. You may already know this. Above my pay grade... I've got a friendly repair man who does that stuff for me for not too many beer tokens. Will have to wait until my return in October now though.
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Post by tonyb on Apr 24, 2021 9:10:47 GMT
My rev counter defaults to 700rpm with the ign off I can't remember if it drops to O with ign on but works fine. Could it be losing 12v after starting thus causing the default of 700rpm?
That is a possibility but it implies that your idle speed is set to 700 rpm hence the 700 rpm when the 12v is removed. In the OP's case apparently it reads 700 rpm whenever the engine is running and at whatever speed. The whole thing makes little sense to me at the moment.
If the counter has managed to get fed from the start circuit then what you say might happen because it would be isolated as soon as the key was released from the start position. However, I can't see how that would happen with just working around the engne.
Hopefully we will see given time.
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Post by Deleted on Apr 24, 2021 9:43:12 GMT
My rev counter defaults to 700rpm with the ign off I can't remember if it drops to O with ign on but works fine. Could it be losing 12v after starting thus causing the default of 700rpm? That is a possibility but it implies that your idle speed is set to 700 rpm hence the 700 rpm when the 12v is removed. In the OP's case apparently it reads 700 rpm whenever the engine is running and at whatever speed. The whole thing makes little sense to me at the moment.
If the counter has managed to get fed from the start circuit then what you say might happen because it would be isolated as soon as the key was released from the start position. However, I can't see how that would happen with just working around the engne. Hopefully we will see given time.
Nothing to do with idle speed that is 850-900 and on idle it reads about 875, plus I have checked the rev counter against a digital tach and it's correct. If I disconnect the 12v from my rev counter it reads 700rpm all day long no matter what the engine is doing. If it has been fed from the starter circuit that would make sense of the anomaly.
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Post by Deleted on Apr 24, 2021 14:31:49 GMT
Well, well, well... I'd like to tell the masses what the problem was but I don't have much of an idea other than I've fixed it! (for now...)
Wasn't able to do much testing as I couldn't on my own reach the alternator and rev dial or the morse control without some fairly significant wiring dismantling (all the neighbours seem to have run off into the sunshine today... ). Whilst waiting for a gullible victim to assist I had a few play arounds with things and came up with a plan to test things to lessen the time needed requiring another body.
Pulled wires off and reconnected them several times, no joy. Then suddenly joy the dial sprang into action.
Best guess is a loose connection, second best guess is a failing alternator (the dial was very sluggish to respond to revs the first few times after it started moving but responds normally now).
Many thanks for all the advice, I'll keep an eye on it and at least I now know where to start if problems start happening again.
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Post by tonyb on Apr 24, 2021 14:37:38 GMT
At a convenient time I would be having a close look at the crimps on the terminals you took off. If you have a large multi-plug on the main engine harness make sure the connection is clean and tight, your boot might have jiggled it.
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Post by tonyb on Apr 25, 2021 10:52:33 GMT
My rev counter defaults to 700rpm with the ign off I can't remember if it drops to O with ign on but works fine. Could it be losing 12v after starting thus causing the default of 700rpm? I have been giving the why much thought. Try this for likelihood.
We know given half a chance the alternator field diodes will try to supply the engine electrics via the warning lamp. I know that when I turned the switch on the Bukh stop the charge warning lamp sort of "wobbled" until it went out. This suggests to me the field diodes were trying to feed the electrics via the warning lamp.
Now being basically electronic in operation the electronics will work on low current but the needle probably needs more to move it.
So when the ignition is turned off I suspect the field diodes supply the rev counter via the warning lamp and as the alternator speed drops so does the voltage & current but initially it is enough to power the rev counter but, in your case, when the revs drop to around 700 there is insufficient current to power the counter so the needle stays where it is. I suspect that speed may be fairly constant across a range of engines.
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Post by Deleted on Apr 25, 2021 12:11:15 GMT
Tony There is no fault in my alternator or rev counter. Alternator has been tested and all diodes are ok, rev counter works as it should and is accurate, checked against a digital tach. Rev counter follows engine revs exactly until the engine is stopped and the ign is switched off then the needle sets at 700rpm. I believe it's a characteristic of early Beta rev counters.
What I was trying to point out is that the OP may have been losing power to the rev counter nothing else.
There is no fault in my systemπ
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Post by Deleted on Apr 25, 2021 12:19:09 GMT
I don't think the fault had anything to do with the rev dial going up to 700 when off (actually over a few minutes of being off the dial slowly rose to nearer 1000 revs) - it acts the same now it is working.
eta. This might help or might just confuse things - when the dial wasn't working but engine running the dial would show 700 revs and stay there, an increase in engine revs would lead the pointer thingy to flutter just slightly but fast.
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Post by JohnV on Apr 25, 2021 12:47:03 GMT
dead fly in the works, left there by a lurking spider ?
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Post by tonyb on Apr 25, 2021 13:09:10 GMT
Tony There is no fault in my alternator or rev counter. Alternator has been tested and all diodes are ok, rev counter works as it should and is accurate, checked against a digital tach. Rev counter follows engine revs exactly until the engine is stopped and the ign is switched off then the needle sets at 700rpm. I believe it's a characteristic of early Beta rev counters. What I was trying to point out is that the OP may have been losing power to the rev counter nothing else. There is no fault in my systemπ I was trying to give you a reason why your rev counter sticks a 700 rpm when the engine is stopped despite the tickover being higher than that, that is all. My VDO did something similar and from the replies so do others. Nothing to do with the OPs problem and I don't believe for a moment its a default reading, if it were the needle would not drop as soon as power is applied to it.
Yes he may have been loosing power to it but in my experience the needle would stick at whatever speed the engine was doing at the time.
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Post by tonyb on Apr 25, 2021 13:12:12 GMT
I don't think the fault had anything to do with the rev dial going up to 700 when off (actually over a few minutes of being off the dial slowly rose to nearer 1000 revs) - it acts the same now it is working.
eta. This might help or might just confuse things - when the dial wasn't working but engine running the dial would show 700 revs and stay there, an increase in engine revs would lead the pointer thingy to flutter just slightly but fast.
Now there is no way I can explain the red bit apart from a fault in the unit itself. Its almost as if a capacitor is discharging itself into the needle driving circuit but without an internal diagram that is just a guess.
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