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What Would Happen?
Do you habitually reach for the wrong switch over and over or pull the wrong handle repeatedly? I do this on so many things.
One thing that I almost do is turn off the battery disconnect every time I reach into the engine compartment. I am in the habit of turning them off if I am parked for more than a week but I do not want to turn them off while the engine is running.
I have a small storage compartment just forward of the engine and behind the tag axle on the passenger side. There was originally a cruise air in it. I store some old hoses and some wood in there. The release for that do is just to the right of the battery disconnects.
When I pull in some where to park and while the engine is still running I often reach in to release the door on that small storage compartment. I find myself reaching for the battery disconnect 95% of the time. Thankfully I have always realized what I was doing before I shut off the batteries. I have had my hand on it several times before I realized what I was about to do.
What would happen if I did turn off the 12 volt or 24 volt switch while the bus is running? Would it shut down the engine? Would it cause damage to the computers or other electrical components?
I will try to restain myself but I am curious.
DKO
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5 Replies
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From my boating days, the rule was to never turn off the battery switch while the engine was running. Reason given was that it would zap the diodes in the alternator. I never tried it but it made sense to me. Cutting off a large alternator current or the field current would induce a large voltage spike (di/dt going towards infinity ~ V). If the alternator was not producing a current when cut off, one might get lucky.
If you just turned off the DDEC supply, the engine would stop. Electronic diesels don’t run without battery power (unless they are in run-away mode). Old-fashioned mechanical diesels would go on just fine without battery.
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Ditto to what threegreens said. There are “Zap Protectors” but I have no idea if our alternators have or even need them.
Great question!
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As a general rule never remove power from anything electrical unless it has been turned off first.
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I absolutely agree that it would not be the proper thing to do. I would never do it on purpose but my hand reaches there nearly every time. I was just wondering what would happen if I accidently turned it off.
It does not sound like it would be good.
DKO
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That type of problem affects almost everybody. Maybe not those switches specifically, but that type of unintended action. That is why in a lot of equipment or vehicles certain switches have a safety cover so the switch cannot be accidently actuated. On our coach for example pocket doors, the bed lift and switches for the dump valves all have safety covers. My plane had several switches with safety covers.
Maybe you need to rig up some type of a guard or latch to prevent accidental operation of the master switch.
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