Engine runs smoother?
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It de-energizes the alternator and takes the load off the engine. You may appreciate how much of a load the alternator places on a small diesel. I had been advised that shutting the key switch with the engine on could damage the alternator but I haven't given it much thought and many times I have turned the off before shutting the engine with no problems.
Benny's right, you should check, but in general, as long as the alternator output is not interrupted, turning off the regulator will not harm the alternator.
It also usually turns off the engine hour meter if so wired to the cockpit panel. And all the gauges, too.
It also usually turns off the engine hour meter if so wired to the cockpit panel. And all the gauges, too.
Stu/Ron
Very interesting. Unlike Ron my Yanmar does not seem to change in smoothness or RPM when the switch is set to "off." There is no doubt the instruments, hour meter, and starter circuit are depowered. So - I looked over a Yanmar wiring diagram - in this case for a 2GM20 with a stock dumb internally regulated alternator. I cannot find anything in that diagram which could "depower" the alternator. What motor/alternator is involved in Ron's case. Wouldn't a disconnect of an internally regulated alternator risk the diodes?
Charles
Very interesting. Unlike Ron my Yanmar does not seem to change in smoothness or RPM when the switch is set to "off." There is no doubt the instruments, hour meter, and starter circuit are depowered. So - I looked over a Yanmar wiring diagram - in this case for a 2GM20 with a stock dumb internally regulated alternator. I cannot find anything in that diagram which could "depower" the alternator. What motor/alternator is involved in Ron's case. Wouldn't a disconnect of an internally regulated alternator risk the diodes?
Charles
Do you have a link to that wiring diagram?
A disconnect of the alternator OUTPUT would fry the diodes. Usually turning off the regulator will not do so. The alternator will be spinning when the engine is running, but unless the regulator instructs the alternator to begin producing amps, it simply will not do so. Many folks, for instance, write in saying: "My alternator isn't working and the tach doesn't work either." The response is usually: "Are you till plugged into the shorepower?" The answer is usually yes. That's because the regulator is seeing a battery voltage higher than its setpoint and does not instruct the alternator to produce.
It's no different than the time delay feature built into smart external regulators.
http://j30.us/files/yanmar-manual.pdf. Thanks for your interest here - and for the explanation.
Charles
Charles
Some of the old Hitachi alts were "self excite" and later ones "ignition" excite. The GM series came with both types "old" and "new" style. Ignition excite Hitachi alts have an L & R terminal and the older style do not have the R just the L (lamp). So some are key on and other are self excite and turn themselves on with engine RPM.
Today many alternators are "key on" you can not blow diodes by turing the key off unless you have a solenoid that is "key on" which makes or breaks the path between the batts and alternator. In order to toast the diodes you need to break the output/B+ under load not the input side turning the key off just turns off the internal regulator and shuts down the output..... Turning the BATTERY switch off with the engine running is the real issue.
That would be true if wired the way the factory did it, alternator output thru the 1-2-B switch's C post.
If the AO is wired to the house bank, ya could turn the switch off if ya wanted to.
Maine Sail's explanation #8 seems right right at engine startup time - see partuculars shown in Claude's diagram - attached at #9. The alternator is "excited" through the charge lamp. Key on provides + to charge lamp thence to regulator circuit. One supposes if no key on, then no "excitement" (engagement) of the regulator thus no charge current delivered. Same arrangement in both A and B wiring plan - terminals L and R at alternator.
So - no matter regulator engagement, there is always continuity between alternator output and battery - assuming alternator is direct to house - not switched.
So - what happens if charge lamp bulb burns out? One assumes no charging at start up. Does that also mean no charging until lamp bulb is replaced?
The question is whether the regulator would disengage (1) at key off and (2) if the charge lamp burned out?
As to the pump - the pump is driven by the motor it is not electric.
Charles
So - no matter regulator engagement, there is always continuity between alternator output and battery - assuming alternator is direct to house - not switched.
So - what happens if charge lamp bulb burns out? One assumes no charging at start up. Does that also mean no charging until lamp bulb is replaced?
The question is whether the regulator would disengage (1) at key off and (2) if the charge lamp burned out?
As to the pump - the pump is driven by the motor it is not electric.
Charles
It depends on where the fuel tank is located. On my boat, the tank is above the engine, and reliable reports from the past 26 years of C34s indicate that the fuel pump (which essentially runs all the time on our boats) can be off until the tank is about half full (height, not capacity). This is because the siphon effect coupled with the meager fuel/injector pump on the engine is enough to get the fuel to the injector pump.
Fuel pumps were/are called "fuel lift pumps" because in many applications, the fuel tank is below the engine, where the boat designer put the fuel tank in the bilge, for example.
In order to find out, determine how full your tank as an experiment. Full tank, turn the pump off, see what happens. Then do it again when your tank is low.
You could also ask on the C27 Association website, I'm sure it's been discussed before.
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