I am still finding issues with my Yam SRV250. The battery isn't charging. I've checked the stator resistances and tracked down to the issue to the reg/rec - although a corroded pin in the connector won't have helped.
Anyway. For some reason there's a brown (ignition live) lead entering the reg/rec. This isn't shown on the wiring diagram and the connector shows the relevant pin to be blanked off. Bothe the existing reg/rec and the generic replacement I've ordered show this wire.
I'm pretty unfamiliar with this kind of setup being happier with Joe Lucas's various offerings. Can anyone suggest what this wire does?
That makes sense. I wonder why it's not shown on the wiring diagram? Presumably there's some sort of relay arrangement inside the black box that closes when the ignition is on?
Don't think so, you should have 3 wires from the alternator, usually white or yellow, an earth connection, a 12V out and a 12V in, usually called a feedback wire, some regualtors have this built in to them and only have 5 wires. The 12V in doesn't need to be switched.
This is really dependant on how the regulator internals work. Historically there was often a way of increasing alternator output when the lights were switched on and this might be a similar thing. When daytime lights became necessary that idea became redundant. I see that there is a connector block shown on the diagram with a brown wire so there could have been a variant for different markets.
Shades of the old PRS8 switch..... That connector block is for the ignition switch. I think it's what Mr Cheese calls a feedback wire. Anyway, I can easily connect it in when I get the replacement unit.
Le_Fromage_Grande wrote: ↑Sat May 18, 2024 3:06 pm
Regulator / rectfiers need a 12V live feed from the battery otherwise they don't charge.
Indeed - modern (relative term ) regulators need to know what the battery voltage is in order to er....regulate...the alternator. They decide how to do their job (which is to control the voltage output by the alternator to charge and then maintain the battery) based on the battery voltage, thus they need to know what that voltage is. So they need to be given a live feed from the battery for info.
You need to control (or otherwise cope with) the alternator voltage becuase it runs over a wide speed range 'cause it's directly coupled to the engine, so it'll have a massive variability in output voltage depending on engine speed. You need some system to correct for that, which can be one of many many different things.
I understand that but am at a loss to know how the voltage seen from the battery will differ from the voltage being supplied by the regulator as they're connected together. I understood that it just limited output voltage to the normal 14-ish volts.
They're a bit cleverer than that - at least, they can be. Lots of them can have higher voltages when they're charging the battery and then drop it when the battery reaches a certain state, thus they need to be able to take an independent read separate from what the alternator is doing.
They also have their own internal 'logic' which needs powering.
Mr. Dazzle wrote: ↑Mon May 20, 2024 6:29 pm
They're a bit cleverer than that - at least, they can be. Lots of them can have higher voltages when they're charging the battery and then drop it when the battery reaches a certain state, thus they need to be able to take an independent read separate from what the alternator is doing.
They also have their own internal 'logic' which needs powering.
So it can sense a difference in voltage between two wires which are both connected to battery live?
Mr. Dazzle wrote: ↑Mon May 20, 2024 6:29 pm
They're a bit cleverer than that - at least, they can be. Lots of them can have higher voltages when they're charging the battery and then drop it when the battery reaches a certain state, thus they need to be able to take an independent read separate from what the alternator is doing.
They also have their own internal 'logic' which needs powering.
So it can sense a difference in voltage between two wires which are both connected to battery live?
In a nutshell, yes Sort of.
That's why you have two, in case there's a voltage drop in the 'main' wires - the ones actually doing the power (almost certainly will be a voltage drop when anything else is switched on). The sense wire, the one in the OP, is supposed to go straight to the battery all on it's lonesome to get a true(er) reading of the battery voltage.
Mr. Dazzle wrote: ↑Mon May 20, 2024 6:29 pm
They're a bit cleverer than that - at least, they can be. Lots of them can have higher voltages when they're charging the battery and then drop it when the battery reaches a certain state, thus they need to be able to take an independent read separate from what the alternator is doing.
They also have their own internal 'logic' which needs powering.
So it can sense a difference in voltage between two wires which are both connected to battery live?
Basically yes, and I had to know how they worked to pass an exam in 1990, but I've long since forgotten, something to do with bridge diode circuits I think.
Its actually an early version of the electric starter system which cuts headlight and other loads while the starter is engaged. Modern bikes have something similar but done electronically.
I've looked at that page but it doesn't answer the question although I note the diagram does show a similar setup to mine (oddly enough he hasn't actually shown the alternator!)
iansoady wrote: ↑Tue May 21, 2024 10:06 am
I've looked at that page but it doesn't answer the question although I note the diagram does show a similar setup to mine (oddly enough he hasn't actually shown the alternator!)
The alternator is the circle with wave symbol in it. The green and red wires are from the trigger for the ignition and the white wires are the AC output.
Colins-SR250.png (336.3 KiB) Viewed 1378 times
At the top of the diagram the rectangular block represents the starter button/kill switch and the blue with black dots wire feeds the lights but is cut off from brown when the starter button is pressed.
This may be irrelevant to your question except that if on your later bike the brown connector is blanked off it is probably because later regulator designs did not need it.
If you are using a generic replacement regulator it may or may not require it. First check the AC output from the white wires and if that is around 18 volts and rising as the engine is revved then the rectifier/regulator is not working. Then try connecting the brown wire to the nearest available brown wire. For a test you could just jump red and brown wires together but as you don't know whether there would be a current drain with ignition off it would be better to use the switched feed ( i.e. the brown wire in the loom).
Thanks, I couldn't actually see the white wires againat a white background....
The original loom and reg/rec have the brown wires connected so I will do the same with my new one when it arrives. Still don't understand how it's supposed to work though although I just have to assume some chap in Japan knows more about these things than I do - which to be honest isn't difficult.
True, but still makes no sense to me being brought up on simple Lucas stuff. The red is the output from the reg/rec but must be at the same potential difference as the brown as it's connected to exactly the same place ie the battery.
iansoady wrote: ↑Wed May 22, 2024 12:33 pm
True, but still makes no sense to me being brought up on simple Lucas stuff. The red is the output from the reg/rec but must be at the same potential difference as the brown as it's connected to exactly the same place ie the battery.
This is a guess: the sensing circuit in the reg/rec box drains a bit of current, so it’s cut when the bike is parked.
) regulators need to know what the battery voltage is in order to er....regulate...the alternator. They decide how to do their job (which is to control the voltage output by the alternator to charge and then maintain the battery) based on the battery voltage, thus they need to know what that voltage is. So they need to be given a live feed from the battery for info.
