Jim, rather than fit a cutout switch I have fitted Discarnect terminals to the earth terminals on my other cars’ batteries. This has a simple hand knob you can turn a couple of turns to disconnect the battery, or simply unscrew it and take it with you as a theft deterrent. The nice bit is that it also includes a small fuse holder that ‘jumps’ the break to keep clocks, radio memories etc. running with whatever inline fuse rating you want to use. That said, you could easily fit a simple fuse holder to bridge your cutout switch. Just remember to carry spare fuses for it! On several occasions I have forgotten and tried to start the car, resulting in a popped fuse when it’s asked to carry starter current.
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I have the 123 blue tooth version on my XK 120 and it is + Earth.
The battery is inaccessible it makes that awkward . I have fitted the cutoff switch to the to the right inner wing . I don’t like drilling extra holes , but as it was a panel I had replaced it felt ok . The switch has a removable basic key .
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Just bypass the cutout switch with a small fuse. You don’t have to have the fuse near the battery and you must be able to access the switch, so a small fuse holder across the terminals would do the trick. If you have a low current fuse in it you won’t need to access it anyway unless you forget and try to start the car, blowing the fuse.
I tried a 9v PP3 both ways on my clock and it seems not to work , not a big surprise with this car . I will put 12v through it and see what happens.
In my picture above I was running the clock with a 500 milliamp 12V trickle charger.
I leave my battery connected all summer, never had trouble with it. I disconnect it for winter and trickle charge it once every couple of months.
Does it tick if you give it a flick? Also, I’m not sure it will start if you just connect power. It may need to be started manually.
There is an instruction on the back of the clock " setting time start it " or words to that effect . I am not sure how good the battery was .I will mess with it tomorrow .
My AC’s ancient Smith’s clock has a chrome adjuster knob which is used to set the hands to the correct time. As Eric says, putting 12V across it won’t start it - I have to press the adjuster in for a few seconds and off it goes. For maybe 30mins or so.
The clock on my MKII will usually start when power is applied. On the few occasions it won’t, as Roger says a small movement of the time adjustment cable is enough to jump start it.
BTW, it’s been running now for twenty years. Keeps pretty good time too.
As I remember it, the handbook for the AC instructs the owner to press the chrome adjuster (which sits on the rim of the clock) in and hold to start the clock. It’s the button top left of the dial in this photo.
Can’t remember if the Jag clock has similar, it’s away in my filing system.
Roger,
I may be wrong, but I think the type of clock that is in your AC is the later Smiths clock. It uses a different principle in that it is electrically wound clockwork. It still has an escapement but the motive power comes from a spring which gets rewound every 90 seconds or so by a solenoid. As it has an escapement, this type of clock will also tick but you can hear a clonk from inside as the spring is rewound. I have several of these and have repaired a few for friends.
The clock in the 140 also has an escapement but the motive power comes from giving the balance wheel a kick each time it oscillates. Without power, obviously the clock will stop but I don’t think it can be relied upon to stop with the contacts closed so it needs an alternative arrangement to start it, usually by engaging the means provided to set the time.
Yes, I think you are right Eric - it is an electrically wound clockwork movement. Would this type work with either polarity, or would the winding electronics be earth-specific, do you know?
Sorry, a bit OT for the Jag clock.
I can’t see why this type of clock would be polarity sensitive unless the spark suppression on the contacts is done with a diode. You can easily check with a multimeter without taking the clock apart. Power the clock so that it is running. Disconnect and look across the terminals both ways round.