On 04/09/2010 02:21 AM, JEFF ROBERTS wrote:
> Tonight before it got too dark I managed to check the following with the
> engine at 2200 rpm's. At first after charging Battery, the voltage check
> direct on the terminals was 12.5. The GG alternator inputs on the
> regulator we're 15.7 AC so I'm assuming the engine is producing correct
> voltage. I checked the +B out of the regulator and it read only .55
> volts DC. Moved the engine up to 3000 RPM's and the +G only went to .55
All right. Alternator is good. Battery is good. Regulator doesn't work.
But wait! This doesn't necessarily mean that the regulator is faulty.
Based on your tests I strongly suspect you have a wiring problem.
Without digging into the documentation: the +B should be connected to
your battery, so it should read AT LEAST the battery voltage, i.e. 11.5
Volts.
Furthermore, the regulator has a connector labeled C, and this is its
reference input. This is where it measures the battery voltage, and uses
this as a decision point how much of the juice of the alternator it
should go "let through".
So, in order for the regulator to work correctly, the C lead should be
definitily be connected to the battery somehow. Ideally, it runs with a
separate wire to the battery, but most folks simply tie it up to the +B
lead, which is supposed to be connected to the battery anyway. (This is
ok, but ignores the voltage drop over the battery cable, which is
minimal in most setups, so for sake of simplicity, just ty it all
together at the output of the regulator).
So, my next suspect is that the C connector is not carrying battery
voltage as well. Which is very bad:
In this condition, the regulator "thinks" that the battery voltage is
way too low, and cranks up the output. But regardless how much it tries,
the C connector will never read the correct voltage since it is not
connected properly. So, even if it outputs 20 Volts, it still thinks
that it should try harder because it measures "a far too low voltage" on
the C connector. You won't notice this, as the output of the regulator
is not connected to the battery.
I hate to tell you this, but in this condition it is well possible to
silently kill the regulator. After that point it will cease outputting
anything at all. And if you replace your regulator, you will kill the
new one as well instantly. Alas, this may be your current situation...
So. What you need to do to get out of this mess:
1) Double check that the minus of the battery is connected to the metal
case of the regulator. Also check that the minus of the capacitor is
connected to the metal case of the regulator.
2) Don't replace the regulator yet. Make sure that, without the engine
running, but the main (battery and alternator) switches to ON, you
measure on the output of the regulator the battery voltage (anything
above 11 Volt is ok). If this is not the case, the regulator is simply
not connected to the battery. It doesn't matter whether the regulator is
defect or not, the output should read battery voltage if it is connected
correctly to the battery. Correct your wiring, switches, relais, fuses,
CB's until you read battery voltage at the output of the regulator. Yes,
all this with the engine OFF, but with the switches in flight condition.
Proceed only to the next step if you have fixed this problem.
3) Run the engine. Measure again. Voltage should increase above 13
Volts. If it does, you most likely have solved the problem. If it
doesn't, you have killed your new regulator and should get a new one.
Most likely you have killed your previous regulator in the same way, but
it doesn't hurt to test it again now you have fixed your wiring. Maybe
you are lucky and it has still some life in it, otherwise you have to
buy a new regulator again.
Oh, and while you are at it, replace the big capacitor as well. If it is
has been destroyed (which is likely in the overvoltage condition it may
have experienced) it will kill a new regulator in a short time.
Note to readers: Yes, you CAN disconnect the regulator from the battery,
but ONLY if you make sure that the capacitor stays connected to the
regulator at all times, and that the C connector is connected to the
capacitor as well, so the regulator "sees" what it is doing. The
capacitor acts as a dummy battery in this case.
Jeff, the best way to avoid this kind of troubles again, is to connect
the C tab to the B tab on the alternator, and run from there a dedicated
wire to the capacitor (without fuses, switches, etc). Keep that wire as
short as possible, and make sure it is a fat wire. Run a dedicated wire
---From the minus from the capacitor to the metal case of the regulator, to
make sure the loop stays always closed. Do not connect anything else to
the capacitor.
Let me know how this works out.
Frans
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