For some reason unknown to Western capitalist running dogs, you can take the keys out of an MZ but leave the lights on. So a few weeks ago when I was in a rush to get to a meeting at work I accidentally did this and came back to a flat battery.
Put the Optimate on it in the garage, came back a few weeks later (I know, but it was winter and I’ve done my time riding in the cold and the wet) and it was flat again. So I brought it into the kitchen (the battery, not the bike) and put it on the car charger.
Built its strength back up, put it back on the bike, this time it held its charge but the red light that warns you that your revs are too puny to run the system wouldn’t go out.
I treated the bike to a new battery just in case.
Thanks, said the bike, but I’m just going to carry on with the warning light.
Now, it seems to me that you should be able to run a bike with a flat battery even if you can’t start it, but it’s different for MZs. In a rare burst of good luck, the new battery had just enough juice in it to get back to the garage and I thought I would see if the headlights brightened when I revved the engine, because I have a vague memory of that revealing whether or not your charging system was shot.
Turned the lights on and the engine stopped.
Yes, we have a problem.
My grasp of electrics is about the same as the Wingman’s grasp of particle physics. I know that a circuit has to go power – switch – component – earth, though sometimes on the MZ it goes power – component – switch – earth. If the circuit isn’t working you have to check that the fuse isn’t blown, that the wires aren’t broken, and that the thing that is supposed to be working isn’t borked.
If that’s a light it’s easy. If it’s a thing with six diodes on it, not so much.
What a man can do, remember?
I have a multimeter, a wiring diagram and the might of motorcycle Twitter behind me.
“How to keep your Volkswagen Alive For Ever” recommends that before starting a new task you should grok the scene. Robert Heinlein is rather out of favour these days, but that’s no reason not to take the advice.
The charging circuit includes the battery, the generator, the regulator and the rectifier. The regulator and the rectifier are under the seat. Like Ant and Dec, one of them has a large shiny dome and I’m never quite sure which is which.
The Blue Book has three pages of instructions on what to test if you’ve got a red light that won’t go out. The Haynes manual has the same but their tests require you to “unsolder” several components – I have a soldering iron but not an unsoldering one, so I am not keen on this!. The Blue Book’s tests just need a bulb and crocodile clips. And by fortunate chance (and an afternoon in a Trabant graveyard having my leg humped by a Jack Russell) I have an actual IFA test lamp. I dig this out in the hope that the bike will feel more inclined to co-operate with the testing equipment of its people.
Electrical fault-finding needs ample supplies of tea, a good desk lamp and a notebook. I’m trying to learn to love it as it’s nice to do some work on the bike that doesn’t leave me clarted with shite or bleeding.
I got to play with my brucie bonus caliper, which would have been better if I’d remembered how to read the vernier scale and hadn’t had to resort to just putting the brush on top of the ruler part to make sure it was longer than 9mm (dear reader, it was.)
I got to refresh several fuses (never mind stockpiling bog roll, I’m going to have to clear Halfords out of 15amp blade fuses if this needs doing again).
Apart from me short-circuiting things several times, nothing actually seemed to be broken.
And then it just started working again. Wiggling the Regulator (or Rectifier) about resolved some sort of earthing problem and that was us.
I’m a great believer in quitting while I’m ahead. Yes, it would be good to understand a bit more about what was wrong and why it’s not wrong any more but I’ll just make sure I’ve put the Communist Test Lamp into the tool kit and keep a scan of the test pages on my phone
Hasta la Victoria Siempre! ( to mix my marxist metaphors).