Potential problem

[sawdust_128]

I was sorting out some magnetic proximity switch issues in the engine compartment lighting group. Later, I started checking the plunger type micro switches on all other bay doors. Much to my surprise, I found that these plunger-types switches have shieding over the sliding contact mechanism. For many of theses, that shielding has been damaged/deteriorated/something else and the contact points are somewhat exposed. These contact points produce a considerable (easily visible, blue-white) spark.

When I found the first one, I spent some time making sure of what I was seeing and then, the aquahot came on in that bay. Fuel and spark in the same bay. I found the same switch condition in my generator bay.

Tomorrow, I am removing those switches and will be replacing them with the magnetic proximity switches. I have a feeling that this sparking is what destroyed the sheilding and it will get worse.

[Jon Wehrenberg]

Sparking is a natural result of opening or closing a set of electrical contacts.

Just because you cannot see the spark does not mean it is not there. That includes magnetic switches. Unless a switch is "explosion proof" it is not gas tight and any explosive fumes are exposed to the spark which you cannot see, but is still occuring, albeit inside the housing which is not sealed.

Sealed switches, especially mercury switches have the spark contained and not accessible to any fumes or vapors. Keep in mind the huge number of spark producing devices besides door switches that reside in the bays, including pump switches, thermostats, motors, and relays.

But in our buses, if we have a device that is allowing fumes in a closed area that is the larger problem than a switch. Step one is to make certain there is no leakage of fuel or fuel vapors. The Aquahot uses a Webasto burner, and the fuel and vapors is contained within the burner head and as part of its cycle a fan is initiated prior to fuel injection to purge any vapors to atmosphere, and after the burn cycle the fan runs for a while to also vent any remaining fumes.

There are thousands of conversions on the road with those switches which I personally don't care for, but they are functional and safe. I wouldn't be carrying a can of gasoline in my bays however. That might be asking for trouble, but around diesel odors I don't think those switches present a hazard.

[sawdust_128]

I'm not worried about the potential for an event because of what I do. I am concerned that the potential for an event could be increased significantly because of what I don't even know what happens when I drive down the road. Then open the bay and quickly mix fresh air, fumes and spark.

For just a few Lewbucks, I can completely eliminate the potential. Plus I'll feel better. I like my coach and my body hair. As you said, there are thousands of these switches on thousands of coaches. However, as my luck runs, now that I know about it, I would probably be the one to end up a hairless, bus-less lurker on the forum. It's why they make 21 flavors.

[Jon Wehrenberg]

Ed, You have all the elements you describe without opening the door. Oxygen remains a constant from the last door opening, and when the mixture of fumes from a leak reaches the proper mixture with the oxygen in the bay and a pump kicks on or a fan starts you just blew your bay doors into the weeds.

But if it makes you fell better it is almost impossible to spark ignite diesel.

That's why I don't worry.