Welding On Class A, Do I Just Disconect The Battery ?

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I don't believe that there is a MH manufacture that disconnects anything when building the MHs. They do a lot of welding on the frames, outriggers, floors, etc., without any problems. If anyone has seen anything different, I would like to hear from them. Even Fleetwood's Power Bridge Chassis, once bolted together, is not disconnected for welding.

You do not have to disconnect anything as long as to knowing what you are doing. Good ground on what ever piece you are welding is very important. But if you are not sure if the ground wire is good, you better disconnect the batteries. But a good ground is even important even if you disconnect the batteries because it could arc in other places, like your wheel bearings.

This is the sticker on my motorhome, Freightliner chassis.
Caution = always disconnect all house and chassis batteries before welding on any part of this vehicle. Failure to do so could cause severe electrical damage

RayChez,
When I started working in a auto shop, at age 17, I also heard the welding on, or around an engine would completely ruin an engine, by welding the rod, main, cam bearing to the crack and cam. Well.....Guess what, there has not been any engine ruined by welding on the block, head, intake, or exhaust. I would imagine that if you placed the ground on the crank snout and tried to weld the block, you might have a problem, but I doubt it, as everything is oil coated. Electricity is like water, it is lazy. It will take the path of least resistance.

If you have a Ford chassis read here:
https://www.fleet.ford.com/truckbbas/non-html/Q123R2.pdf

wildmanbaker wrote:
RayChez,
When I started working in a auto shop, at age 17, I also heard the welding on, or around an engine would completely ruin an engine, by welding the rod, main, cam bearing to the crack and cam. Well.....Guess what, there has not been any engine ruined by welding on the block, head, intake, or exhaust. I would imagine that if you placed the ground on the crank snout and tried to weld the block, you might have a problem, but I doubt it, as everything is oil coated. Electricity is like water, it is lazy. It will take the path of least resistance.

Great post wildmanbaker. And you are absolutely correct on your last sentence: Electricity will take the path of least resistance. And that is why it was so important to have a good ground on clean metal. I was a mechanical supervisor for many years where they done a lot of welding, stick, mig and even spray welding and the ground was very important.

wildmanbaker wrote:
RayChez,
When I started working in a auto shop, at age 17, I also heard the welding on, or around an engine would completely ruin an engine, by welding the rod, main, cam bearing to the crack and cam. Well.....Guess what, there has not been any engine ruined by welding on the block, head, intake, or exhaust. I would imagine that if you placed the ground on the crank snout and tried to weld the block, you might have a problem, but I doubt it, as everything is oil coated. Electricity is like water, it is lazy. It will take the path of least resistance.

I think the big worry is the engine's many computer and related components, and not the engine itself. Things like the cpu and even the dash cluster.

carringb wrote:
If you have a Ford chassis read here:
https://www.fleet.ford.com/truckbbas/non-html/Q123R2.pdf

Models Affected: All F250-550 trucks; Model Year 2008 and later.
Action Requested: Please provide a copy of this bulletin to all Engineering, Manufacturing, Service, Parts, Sub-
Contractors and Customers that plan to use this vehicle as a mobile welding platform.
Recommendations: Perform the following operations prior to any plasma cutting/welding operations on new vehicles.
Following completion of the plasma cutting/electric welding operations, reconnect all disconnected
units in reverse order.
1. Turn the ignition switch to the OFF position and remove the key from the ignition switch.
2. Disconnect all battery cables from all batteries.
(Refer to Attachment I and II)
3. Disconnect all three connectors from the Powertrain Control Module.
(For diesel engines refer to Attachment III, steps 1-5; for gas engines refer to Attachment
IV, steps 1-2)
4. Disconnect all seven connectors from the Smart Power Distribution Junction Box (SPDJB).
(Refer to Attachment V and VI), steps 2-4)
5. Disconnect the ABS Module connector.
(Refer to Attachment VII, step 2)
6. Disconnect the fuel tank connector or connectors (dual tanks) from the fuel sender on the
fuel tank.
7. Disconnect Instrument Cluster connector. (Refer to Attachment VIII, steps 2-7)

After reading this makes me wonder if even I should go ahead and weld on my motorhome, maybe hire someone with more knowledge and business insurance just as a backup..

Thanks for the replies..

The arc creates Radio Frequency energy that is radiated. This energy is made up of many very high voltage spikes that can destroy modern solid state devices. A good ground can help prevent or reduce the amount of radiated energy.
Disconnecting sensitive electronic components such as ECMs is to prevent that type from EME (Electro Magnetic Energy)from damaging them.

The very first radio transmitters were simply arc generators that were turned on and off to send the dots and dashes of Morse Code. They were known as Spark Gap Transmitters. This is why radio operators were often called "Sparks". Spark Gap transmitters are now illegal since it is impossible to tune them accurately.