Ammeter not reading.

[simon.holyfield]

A couple more useful pictures

[Ian.Lindsay]

Here you go. That's a repro ammeter - original ones don't have the clamp bracket, but are retained by tabs on the rim as has been said.

Yes that looks like mine (or at least the subpanel shape looks correct. On mine it doesn't look like a separate panel but, like you say, it might have been painted fully assembled. I'd like to keep it that way without breaking the paint so might be a bit fiddly to sort out. Not sure if my ammeter is 6v or 12v but I'll take it out of circuit and just connect a multimeter into the circuit and it'll tell me what's going on when I put a load on the circuit or start the bike. What's the ideal charging voltage for a 6v system? I can put a power supply onto the bike ammeter to see if it works under 6volt and if not I'll try it on 12v. I'll just put a couple of Amps through it. I should be able to do that with the ammeter in situ if I rig up some leads for the regulated power supply. The link looks quite useful. I suspect one of those wiring diagrams is the right one for my bike.

[will_curry]

For what it's worth, ammeters aren't voltage-specific.

I reckon on setting Lucas control boxes to around 7.2v.

[Ian.Lindsay]

Right I've just had another look at it in better light and the sub-panel can be unscrewed from the main headlight housing. However, It can't be pulled out from beneath the yoke and headlight unless I unbolt the headlight and drop the loom down. However, as I'm not messing with the light switch it may be better to just take the light unit out and and work inside the headlight housing instead and then I don't have to reset the headlight beam.

I can confirm that the ammeter is the peened over tab type so I'd rather leave it in place (disconnect one side and put a test meter across to see what's going on) and test it in situ until I can confirm it is actually dead or wrong type. Looking at the circuit diagrams you linked to and, if I'm understanding it, the fact I'm seeing more than battery voltage at the battery means the regulator is working and passing a charging current across the ammeter without the needle deflecting. Without the ammeter in circuit the regulator wouldn't charge the battery. Does that sound right?

The only question now is what is a reasonable charging voltage I should see at the battery, so I know I'm not cooking the brand new one I've just bought? The old one must have failed for a reason (hopefully lack of use and not overcharging). So as long as it's a reasonable charging voltage the lack of functioning ammeter isn't an urgent issue and I'll just keep an eye on the battery until I can sort it out.

PS. The undated wiring diagram is probably closest to mine I think. I don't have an ignition switch or ignition tell-tale light and no key with the bike. You just jump on it, kickstart it and away. They mustn't have stolen bikes bike in 1954.

[Ian.Lindsay]

For what it's worth, ammeters aren't voltage-specific.

I reckon on setting Lucas control boxes to around 7.2v.

Yes, actually that's true isn't it regarding ammeter being independent of voltage.

Are you referring to the charging voltage being 7.2v? I don't think this bike has a Lucas regulator and not sure if it's adjustable. I think I measured slightly less than 7v when I started it up last night. Sounds like it should be OK. Cheers.

[SteveShone]

Perhaps this is worth investing in - an excellent book
https://www.amazon.co.uk/Classic-Motorc ... 1847979955

or his website that could answer all your questions
https://www.matchlessclueless.com/

Steve

[simon.holyfield]

Charging voltage should be around 7.2, but you might need to rev the engine a bit to see it.

Couple of other points - my bikes all have LED lights. The ammeter may not move much, depending on its measuring range (normally 8-0-8). Secondly, if the battery is fully charged, the ammeter won't move much, or at all.

[Ian.Lindsay]

Another useful link there Steve. Yep mine's an 8-0-8 Simes. Thanks everyone. I'm on it.

[Mick D]

Hi

If there's nothing obvious when you look at the wiring I'd start by checking out the ammeter. Disconnect the wires from the terminal post, (making a note of where they are fitted), and tape the ends to avoid accidental contact / arcing. Place the probes from a multimeter, set to resistance on the terminals and observe the reading. If you see a reading of a few ohms the ammeter is probably OK internally, if you see 0 ohms, (open circuit), the ammeter is broken and if you don't think you can repair it, should be replaced. You might like to leave the old one in place until you can temporarily fit a replacement into the loom to confirm you've fixed the issue If there is continuity at the ammeter, (indicated by a low ohms reading), make a simple test circuit - run a wire from the battery to a head or tail light bulb, from the bulb to the ammeter and from the ammeter back to the battery, the bulb should illuminate and the ammeter needle show a deflection. If you see a deflection swap the wires at the ammeter terminals and the deflection should reverse. This indicates that the ammeter is not at fault and it's time to investigate the wiring and components in the associated circuit. If there's no deflection it's most likely the needle mechanism is seized, get a new ammeter.

Regards Mick

[Bob.Murphy]

Err, ammeters should have negligible resistance - they pass the current straight through. Voltmeters should have infinite resistance.
Bob.