Clattering Start Relay - Convert

I fancy I need to carry out Brian UK’s modification on my 1979 Convert; but is it more serious?
When the battery has been fully charged (on a charger) the engine will start normally but, after a run, all that happens is that the starter solenoid clatters and won’t stay engaged long enough to start the engine.
After start-up, the charging light doesn’t clear until the engine has been “revved up”, after which it remains out except at very low idle. The charging voltage, however, never rises above about 13.5, whatever the revs. This might, of course, imply that the battery is charged and requires no higher voltage…
I thought I had fixed this by replacing the ignition switch (the contacts had disintegrated) but now I’m concerned that the battery isn’t being fully charged.
Any suggestions?

If your charging volts does not rise to 14.5 volts then you have a charging problem.It could be caused by a duff bty ( battery) but probobly not in this case.Clean up your main bty -ve collecting bolt under the bty (bty tray) first. Remove it and also clean the hole it goes into.Then look at your brushes, and leads / connections to them.Then the 3 ac leads from the alternator to the rectifier.Contact cleaner not WD40 is what you need.

I would start by removing the alternator cover and checking the condition of the two slipring brushes and make sure the have not worn out or are sticking a bit
failing that its check that the voltage regulator is working , (would consider if in dought replace it with a modern one from euro electrics) they are designed to start charging at a lower RPM than originals
chech wiring to rectifier etc

the reason it is chatering is usually because the battery is not charged enough or there is a bad connection on the battery - take them off scrape clean and refir with a blob of vasalene

happy hunting

(Bloody hell Ian types quicker than me)Ex smokingbiker2013-07-30 11:24:46

What are you using as a Voltmeter and is it accurate. If it’s less than 12 that’s when it’s not charging and you need to worry. 13.5 (if correct) is plenty good enough. How old is the battery, how often is it charged or how often bike is used etc. It could simply be battery failure, dead cell etc.

That chattering, or machine gunning as it’s otherwise called is very symptomatic of a dud battery.When you press the start button the solenoid pulls in, but the extra load of the motor drops the battery voltage sufficient to cause the solenoid to drop out. Immediately the battery volts recover and the solenoid pulls in, and so it repeats.You need a new battery.

Thanks, guys, all very logical and helpful. In particular, Brian’s reply is the same as my first conclusion.
Incidentally, I’m using an alternator checker (six leds, 0.5 volt increments). This instrument enabled me to diagnose a low-output alternator on my Mazda Bongo last year after I had (mistakenly, it turned out) replaced the battery!
I cross-check my alternator checker with a digital multimeter-not necessarily the world’s most accurate instrument, but probably not more than a few tenths of a volt out.
My logic tells me that a fully charged battery should not be getting 14 volts even from a fully serviceable alternator (correct me if I’m wrong); and Brian’s description of the clattering accords perfectly with my symptoms. The battery came with the bike five years ago (it was stated to be new) and is stored on an Oxford “Maximiser”.
I will try to borrow a full output tester.

If batt is showing symptoms of internal resistance (i.e., is kaput) it won’t matter how ‘charged’ it looks. Again this is suggesting to me a dud cell, it’s that kind of behaviour. It’s 5+ years old, so no great loss to get another. Most I’ve had out of a battery is about 7 years so it’s getting close, speshly depending what ‘new’ actually meant. I presume up until this moment all was hunky-dory, bike working and alternator charging and everything, which further indicates batt has decided to expire of old age. HTH

Not QUITE hunky-dory, Mike; I had some starting problems before (the battery kept going flat, which is pretty rough treatment in itself) but my investigations revealed that the ignition switch was faulty (broken contact) so I replaced it last year. Since then it has been ok. It’s always taken a hefty “blip” of throttle to get it charging, but the machine-gunning has only been evident when the battery was becoming exhausted.
I did check out the brushes and slip rings whilst hunting the last problem, so I think they’re probably ok, although it won’t hurt to check them.
I would be happier if I could get 14 volts out of the alternator though.

If you have a V1000 Convert get a Lead Acid Battery replacement 5 yrs is about normal for one really I have had more but not often.They get a fair bit of vibration through them.

The lead acid one gives the Bosch starter more oomph for longer which they need and the Convert like any automatic is more reliant on the battery and starter and you can’t bump start them

The charging system does not go through the ignition switch but is permanently connected up to the battery (well the rectifier part is), so it’s now looking like this is your old problem that has still not gone away. As suggested please check state of brushes, slip rings, wiring, connectors etc. MG manual says the following:Max. current: 20 Amps (280W - 14V)Start of charge: 1,000 rpmField (rotor) winding resistance: 3.4 Ohms3-phase stator resistance: 0.36 Ohms Power test: max. output @ rpm: 5A @ 1,300 rpm; 10A @ 2,100 rpm; 20A @ 7,000 rpm One of the suggested causes in trouble-shooting chart for ‘battery discharged or insufficiently charged’ is ‘obstruction [resistance] in charging circuit’, hence check connectors are clean and tight.
Mike H2013-08-03 20:10:07

Sounds more like a diode out in the rectifier. Possibly one of the small ones which feed the rotor winding. That would cause the light to stay on longer.

All good, but the broken contact in the ignition switch was (sometimes) causing a short whilst the ignition was switched off; that’s why the battery went flat a couple of times while I was at work.
I think the battery is now knackered but I also think there’s a phase out on the alternator. I’ll be checking that out when I get a round tuit-I’ve got one on order and it should come next week!
Great stuff, guys, thanks a lot.

I think so too, time to get the multimeter out. Some DMM’s have a diode test function too.

On the Convert the diodes can be replaced fairly easily,

Well, I got my round tuit today so I set to and started poking around. Slip rings and brushes ok, all earths and connections intact.
I think it’s the rectifier. I disconnected the battery, switched the ignition on and tested each rectifier spade terminal in turn; with the +ve probe to the terminal and the -ve to frame I get 186.7K, 186.7K and no reading on the third (right-hand) terminal, i.e. no conductive path either way.
If I’m right, it’s a diode. OK Guzzibear, if it’s that easy I should be able to fix it if I can get the part. Any ideas?
Presumably, I unship the rectifier and do a little careful soldering on the back. Will all become obvious once I get it to bits?

To be thorough you also want to repeat that test for opposite polarity i.e. negative lead of meter to AC inputs and positive lead to rectifier’s + output battery connection. But if you got a failed diode would explain the non-charging problem perfectly.

Years ago when members joined the club, we were given a clip folder of 30 some pages of hints and tips. I still have mine, and this is a copy of the rectifier page, it might help.

Thanks for the diagram, Al; I’ve now completed that part of the test (the rectifier checked out okay) and I’m ready for the next level!
I’ll be checking the solenoid and motor (once again, just to be sure) and then I think it’ll be time to find a man with a drop-tester to check the battery’s ability to sustain a high current.
I suspect the regulator is not within my technical capabilities, but I’ll take a look at it anyway; burn-marks would be a dead giveaway.
One thing I know about electrical stuff: it all has smoke inside and, once the smoke gets out, it never works properly again!

If you have a Bosch starter and suspect the solenoid may be faulty, there is a good guide to stripping it hereWhere abouts are you? I have a spare regulator and rectifier, you could try. I am in South Leicestershire.

There is a guide to testing the starter motor and solenoid in the FAQ section.