DavidExpert

Just a quick update some days later; with the boat blacking done I could finally get around to swapping the old alternator for a new one today. The old one came off easily enough, the new one largely went on without too many issues though as someone suggested, I did have to swap the (thin, v-shaped) pulley on the new one with the old (lots of little v-shapes) pulley. That was a right palaver, since I lack the appropriate tools but a large spanner on the pulley nut (banged with a lump hammer) with a screwdriver simultaneously shoved into the old alternator to stop it spinning gave me enough leverage to get the old one off. The new one I had to use the same technique for but a bit more carefully since I didn't want to mess the new one up. Managed it somehow, swapped the pulleys, installed the new one and it works (well, the batteries immediately showed 14.5V as soon as the engine started, having previously been showing 13.something with the engine off). So once again thanks for all the help. (edit) Oh, and should also mention that the new alternator is not steaming hot while everything's off, either!

Crikey. I'll have to get it delivered to where I'm having the blacking done but hopefully they'll have a Man With A Wrench who can sort it. Many, many thanks for the help. Now if I could just sort this wretched oil leak and the (new) diesel leak...

It does sit in a hot engine bay with no side slits in the hull for air. Also, for all I know it's the original (17 year old) item so maybe it's just had its time. Anyway, I will order a replacement and many thanks for the prompt, useful and understandable help! Cheers

I disconnected the B+ wire (from alternator to isolator to leisure bank) and reconnected the relay exactly as it originally was; turned the isolator back on and the relay remained disconnected, the control terminals showing 0V across them, and the starter battery showing 12.5 with the leisure bank at a paltry 12.3. I will leave it disconnected overnight and rewire before plodding on tomorrow - I'm due to have the boat out on Monday for blacking and a BSS so this alternator issue is really badly timed! Any ideas what on earth would have caused it to fail? It does explain why I thought my leisure batteries were shot when I set out a week ago, they must have been draining nonstop and they're quite ancient anyway!

Great, thank you. So source a direct replacement and swap it in? (unless one can swap in better alternators,min which case suggestions welcomed). I have disconnected it and wrapped the end of the wire in vast swathes of gaffer tape to prevent any contact with the hull while it lolls around in the engine bay.

I am going to go and do that now. With apologies for the torrent of queries, does this diode fault mean that the alternator might as well stay disconnected because it won't be producing any charge when the engine's running anyway?

Thank you Tony. The ignition (switch) is off. I have pulled off the wire I mentioned and this appears to have separated the battery banks as they are now at slightly different voltages. The "extra" wire disappears into a wrapped collection of largely brown wires but beyond that I can't easily see. i was scanning canalworld for VSR info as it seemed like a better solution but there were assorted posts stating various issues with them as well and "for that reason most boaters stick with a regular relay". It's all very frustrating and complicated.

Actually it is - hooray. It's a single switch which has two separate sets of connections, one to the starter motor & battery, and the other pair for the leisure circuits. I also notice the alternator is wired to the leisure side not the starter battery. So the sequence of wires is: starter battery->isolator->starter motor->relay->alternator->isolator other pair->leisure bank. presumably this also means that despite switching off the relay (by disconnecting its earth lead to the alternator), the faulty alternator will sit and drain the leisure bank overnight. Many thanks for the continued assistance.

Here's a not terribly good pic. Am I right in thinking that disconnecting that +ve means I've got to be very careful the spanner doesn't touch any of the rest of the alternator as that'd be ground and then there'd be a big bang? I didn't understand a word of that, sorry but I don't have any lights on anywhere although I'm not sure I even have a "charge light". Ignition is off though inasmuch as the switch is off and the key is out

Thank you. Is that something I get can get fixed cost-effectively or do I realistically have to buy a whole new alternator? Thank you.

If it were a voltage-sensing relay then I imagine that would make sense (and indeed be desirable perhaps). It isn't though, it's one of those relays that has a distinct "trigger" across two pins of the relay and that should normally be off unless the engine and alternator are on. Or, has someone transformed it into a VSR by virtue of connecting up the leisure bank to it? I suppose it depends what voltage the relay needs to trigger but it seems odd in my limited understanding of these things.

Hello After some work was done on my engine recently (not by me), I noticed the starter and leisure batteries were showing exactly the same voltage which seemed unlikely. Several measurements were taken and in each case this was true. For reference, i have 3 x 110Ah AGM leisure plus one 95Ah starter. Charging is from alternator through split charge relay, Victron (when on shoreline which I am not at present) and MPPT solar. The voltage across the relay's trigger pins is 12.0V. The solar is currently sticking 13.2V into the batteries which I have also measured across the alternator terminals. The alternator is getting quite warm which alarms me. Moreover, when the sun goes down this evening, i will presumably be drawing fridge power etc from all the batteries instead of just the leisure ones. Being very non-expert at this, should I - for ease until someone can look at it next week - simply pull off the blue-capped wire that goes to the alternator earth (number 85 on the relay) overnight so as to de-energise the relay and only drain from the leisure bank? I also noticed while cruising yesterday that the voltage (being observed on the solar charge controller) never went above 13.2 but I'd have expected the alternator running to shove it up more than that unless maybe the relay de-activated itself while engine running (in which case I'd merely have seen whatever the solar charge controller was putting in which may be 13.2 perhaps) I have attached a pic of the relay connections. There are three wires going to "86"; one with a blue tip stems from the alternator and I would presume to be the expected trigger for when the alternator is running. The other (yellow-tipped connector) has a (disconnected) Adverc brown wire plus another brown/black wire which disappears off towards the starter motor with the +ve cables from 87, possibly (though I can't see it) onto the starter motor +ve as this is where the cables from 87 attach. It's all a bit peculiar because I thought it had all been put back the way it started, and it's been like that for the last two years since I had the relay replaced. Thanks David

Fair point and apologies for not updating here. All sorted and filmed now, thank you. Regards David

Can you help? A small fee is on offer :-) I have been asked by a client to film a video about how a lock works, to be aimed at children. For this I need to find a willing boat and crew to be filmed. The script is written and now I need to shoot it. This will involve me scurrying about at the top of a lock with a small camcorder while the boat goes through. I’ll be taking various shots at various angles of, for example, the gates being opened and closed, the paddles being operated and so on. There is a slight complication from the fact that in order to get all the different shots, I really need the boat to go through the lock several times – BUT I reckon instead that if the boat goes down a lock flight ie at least 3 or 4 locks, I can get the variety of shots just by following it down the flight. Furthermore, I will need time to get ready for each shot (focus, compose, exposure etc), so the boat being filmed and the people working the lock would need to be patient and wait for me to say “go” before doing each bit, rather than going through at normal pace. Obviously, if we were holding anyone up we’d need to let them go past. I have a £50 fee available to the boat willing to help me on this (one boat only!). It’ll need to be a lock flight somewhere in the south midlands as that’s where I’m based so I’m thinking Hatton / Stockton / Braunston / Buckby or similar. I’d rather not do a staircase lock as that’ll just confuse things. Boat crew must be experienced lock hands. If you are able and willing to do this (by the end of July ideally), please get in touch via http://cruisingthecut.co.uk/lock-filming/

Unfortunately I can't tell you because, being rather ham fisted, I let loads of it out as I was attaching my air pump to the little nozzle thing, before the marina guy came over with a pump with a gauge on it and said "it's a big high, I'll let some out" and let even more out. So, yes, all a bit odd but the marina chap says it's now at the right level (and he knows his stuff, I believe) and it certainly works the taps much better. Apart from the two runs overnight last night though, it doesn't seem to have run spontaneously all day. Hmm, so the pump may still need replacing? Or can you get spare "bits"? It's a Shurflo pump.