Use Caution When Welding on an RV

A motorhome is a sophisticated maze of electrical systems. In addition to plain old "wiring, bulbs, and things" there are a number of high tech electronics devices in our "entertainment centers on wheels". Plus, today's vehicles are heavily dependant upon microprocessor control. Even the transmission has it's own computer.

Whenever you attempt to repair a vehicle by welding, you induce a pretty good current into the frame of that vehicle. Because virtually every electrical device uses the chassis frame as it's grounding connection, you can easily see how this higher voltage stray pulsing current isn't going to help any of those devices, especially the expensive computer based stuff. There's an old joke about all those computer chips being hollow and filled with gray smoke. If the gray smoke ever leaks out, you're computer won't run.

Therefore, whenever having any welding operation done, you must disconnect the electrical system. Naturally this means the 120 volt shore power, but also any 12 volt systems must be disconnected. Look very carefully at the battery bay. Chances are that the main power leaves the batteries and goes to a master disconnect switch. You may have one switch for the house batteries and another for the chassis batteries. These both need to be in the OFF position before welding on your coach. In addition, there may be certain items connected to the batteries before the disconnect switch. Sometimes larger current loads, such as inverters, are connected prior to the disconnect switch. If you are not sure, remove the negative battery cables. By eliminating any connection to ground, you will break the circuit to these items.

Remember, you need to know this even if you are not planning on doing any welding. Someday you may have a repair done by a service facility and the welder may not understand the importance of this so you'll need to make sure that this is done or else you are in for some more repairs.

Submitted by Mark Quasius - 9/17/08
 

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