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By thegasguy
#1563746
I have studied the B and C wiring diagram and compared it to the (new) wiring in the Jodel, I can find no obvious difference and yet the low output persists.
A revelation on the B and C website 'FAQ'S is that there is an adjustment screw somewhere on the regulator that will 'up' the output !
Supposedly this is factory set to 13.5 V or so, but maybe mine is set too low? I'll find out tomorrow.
Anyway, what several hours of study has thrown up is that the 'alternator warning' light seems to be no such thing. Opinions required !
It illuminates when the alternator half of the master switch is off (but the 'battery' half has to be on, to provide power to run the light), because a relay is not energised and the bulb is connected through the NC (normally closed) contacts to power and earth. The engine is not runnng at this point so it warns that "no power from alternator" is the case.
So far, so not very clear I'm sure!
Next ,purely to explain how the circuit works if you follow the wiring diagram supplied, the alternator half of the switch is turned on.
The relay is directly energised by this and the NC contacts become open and the bulb is disconnected- and goes out.
It's sort of telling the pilot that there is no problem, that power is being generated, but common sense tells us that it isn't- we haven't started the engine yet.
Ok so far.
Start the engine, - light stays out as power is there from both battery and alternator keeping the relay coil energised.
All good.
Now, imagine the alternator suddenly fails to generate at all for some reason. The light will stay out as it is disconnected all the time that the relay has energy from the battery to keep the relay held open. That relay is tiny and uses virtually no current, when the battery has discharged to the point that it can't keep the coil energised it probably won't be able to illuminate a bulb, it certainly will be totally flat for all practical purposes such as runnng any lights or instruments.
This seems silly to me, surely a bulb that is un-illuminated by the alternator output alone ( if you see what I mean) is the proper thing to have.
As soon as the alternator gives up the ghost a nice yellow bulb illuminates and you still have 100% battery left.
B and C seem to be an excellent firm that make very reliable kit so I'm probably missing something obvious, what is it please ?
User avatar
By Flying_john
#1563785
What you have described is how the BandC Alternator warning light works. It is only warning you that either the switch is off or the crowbar has operated, not whether it is producing current.

It is not like a conventional Alternator lamp where you would get a flickering light as the alternator / generator came up to speed and when one side is connected to battery and one to generator and as the voltage equalised the light would go out .

What tells you that there is no charge is either the low battery voltage light or the ammeter.

Its not like a car ignition light.

You still need to measure terminal volts on battery (no engine running) then again with engine running at the battery terminals as the first test.

The tests that follow depend on the result of this test, but follows what has been discussed earlier in the thread.
By thegasguy
#1564122
Here we go again!
Thanks to all the Stoneacre boys for their help on Saturday, all in vain I'm afraid.
For those 'outsiders' who may be following this thread, the wiring was checked by enough brains to eliminate that as being wrong, ditto the alternator windings.
In the end a new battery seemed to fix it, the B and C website having given that as a possibility.
So, off on a half hour flight to Damyns Hall today - 13.5 volts all the way, nothing turned on but a couple of instruments to give the battery a chance to charge a bit.
Coming back it didn't really crank that smartly and I was only seeng 12.5 volts in the cruise with the strobe on.
I put on the landing light and the voltage crashed, warning light on - the works.
Then it was 12.2 volts even at max rpm and nothing on.
Back to square one, the system is only capable of running an EFIS and occasional radio without dying- its as weak as a kitten.
Got to be the ( brand new) regulator surely ?
It seems to "mirror" whatever the battery voltage is at any given time, holding it at that.
Anyone ever head of that?