Welding on an Road Master Frame

[Discover 17]

 

2006 Signature 45' 600 Cummins / Allision with tag.
I am in need to repair the driver side rear drive axle front shock mount and the arm mount on the passager drive axle. I searched form the topic with no sucess. Was wonder if anyone have knowledge on this issue. My concern is all the electroic - computers and the Aladdin system issues when welding. I believe the batteries should be disconnected? Should all the grounds connection be disconnected on the frame as well? I understand the transmission has a ground on it as well. If so where are all the connection at. The electrical drawing do not show location. I would appreciate any assistance on the subject.
Thanks in advance.

[Ivan K]

When I did some minor welding on ours, I physically disconnected the batteries at their posts and isolated the positive cable ends. Of course, unplugged from shore so there is no power source anywhere. Clamp the welding ground cable as close to the weld as reasonably possible so all the welding current goes through that short solid section instead of looping through the frame. Worked for me.

[David Pratt]

As Ivan has stated, you must remove all the cables from all the battery's-House and Chassis including grounds and Positive cables. Disable the Solar Panels and disconnect from shore power-Unplugged. Also as a Safety Measure turn off all the Battery Cut Off switches.

[GNRACN]

Do all of the above and touch grind to bare metal as near as possible to area to be welded for ground clamp.

Watch for burning under-cote and plastic air lines if your doing it yourself!

[Bill R]

Rookie question here, as I know NOTHING about welding.  If I am having an exhaust shop modify my exhaust system, requiring welding, do all of the suggestions regarding disconnecting batteries, grounds, positives, etc., apply?

[Tom Cherry]

15 minutes ago, Bill R said:

Rookie question here, as I know NOTHING about welding.  If I am having an exhaust shop modify my exhaust system, requiring welding, do all of the suggestions regarding disconnecting batteries, grounds, positives, etc., apply?

What I recall….and folks debate about overkill and such.

FIRST, assuming you have the lighted key pads for an Intellitec MPX system and have NOT jumpered the salesman switch.  Turn off the “battery” or salesman switch on the panel as you enter  the MH.  Then follow the steps….in reverse order….so repowering your Intellitec EMS will be the last step .

Turn off both battery disconnects.  Remove the positives and negatives from each bank, house and chassis.

Unplug every device plugged into an AC OUTLET.  TV and microwave and any home entertainment system.

Turn main 50 A breaker off

Use a battery jumper cable and ground or attach the cassis to a steel, presumably a building column or such, that IS GROUNDED to the electrical service in the repair shop.

Others may say, rightfully so, this is overkill….  But, we each have our own comfort level.  If one of the above is a NO NO, please correct.

[Ivan K]

13 minutes ago, Bill R said:

Rookie question here, as I know NOTHING about welding.  If I am having an exhaust shop modify my exhaust system, requiring welding, do all of the suggestions regarding disconnecting batteries, grounds, positives, etc., apply?

It doesn't matter which part is being welded if electrically attached to the motorhome. You just don't want the much higher than usual voltage reach the sensitive parts in some way.  Having the solid ground clamp connection close helps to prevent it. I start the weld at the part where the ground is, not the part that is to be attached and may not have the shortest path to ground yet. Back when I used to go to shops with my cars, I have never seen them to worry about it however, maybe different now with cars loaded with electronics.

[Discover 17]

Want to thank all of you guys for the input and advise to help me prevent electrical system problems on my coach. Thanks again

 

[Jdw12345]

Not to correct anyone but I was under the impression that you should disconnect the ecm on the engine and the transmission, I’m assuming that by disconnecting all of the batteries and turning off the master switches to house and chassis batteries that supersedes the actual disconnect on the ecm’s, is that correct?

 I need to do a couple of small welding repairs also!

  Thanks!

[Chargerman]

Yes, that is correct, ECM on engine and transmission need to be disconnected per Monaco. 

[Jdw12345]

2 hours ago, Chargerman said:

Yes, that is correct, ECM on engine and transmission need to be disconnected per Monaco. 

Ok thank you, so, were are those connections?

Edited October 26, 2023 by Jdw12345

[b_faster]

I did some welding on my chassis, near the front.  Isolated the batteries/shore power.  Then put the ground clamp as close to the work area as possible.  Once the path to the ground is established, the risks of stray currents/voltages in other systems is going to be reduced. 

 

Be mindful of control wires, hoses, etc., as it is near impossible to be far enough away from those items.  There is a risk from both a heat and induced current, so isolation and shielding should be done carefully near the work area.   I suspect that Monaco's recommendation was "covering their bases".  

[dl_racing427]

Disconnecting the engine and tranny ECU's, as well as the connector at the tranny itself, is very important.
I agree with the other suggestions as well, particularly the welding ground clamp close to the weld.

I also understand that the high frequency start on many TIG welders should be turned off, as it can induce high voltages in the chassis and wiring of the coach.

[Deepseated]

You are more at risk of burning/melting stuff than stray current affecting components. We used to weld sensitive areas by using a double ground on both sides of the work area. 

[Tdkkart]

Multiple schools of thought here, ranging from doing nothing at all, all the way to disconnecting and grounding everything.

Talk to a bunch of welders that weld on trucks and heavy equipment(most of which today has as much electronics as our RVs)  every day and I'll be that 80% or more do nothing other than make sure the ground is as close as possible to the welding.

Disconnecting ECUs?  I'd be more worried about some mallet-fisted welder damaging the connectors than smoking the electronics.

 

[dl_racing427]

31 minutes ago, Tdkkart said:

Multiple schools of thought here, ranging from doing nothing at all, all the way to disconnecting and grounding everything.

Talk to a bunch of welders that weld on trucks and heavy equipment(most of which today has as much electronics as our RVs)  every day and I'll be that 80% or more do nothing other than make sure the ground is as close as possible to the welding.

Disconnecting ECUs?  I'd be more worried about some mallet-fisted welder damaging the connectors than smoking the electronics.

 

Good point on the connectors.  Also, some ECU's can be a bit difficult to access.
I would at least disconnect the connectors at the transmission, as that ECU is a long way from the tranny, which increases the chance of a voltage drop across the frame length.

[Tom Cherry]

3 minutes ago, dl_racing427 said:

Good point on the connectors.  Also, some ECU's can be a bit difficult to access.
I would at least disconnect the connectors at the transmission, as that ECU is a long way from the tranny, which increases the chance of a voltage drop across the frame length.

Probably OK...but the TCM, usually UP FRONT, will still be connected..  I THINK...would have to look at how the wiring is done.  IF the feed from the Chassis battery to the TCM is routed THROUGH the Allison....via a direct feed...and then the TCM is fed or wired without any + 12 VDC from the chassis...YES, pulling it there would work.

I don't KNOW....and am NOT saying that the advice is wrong....only 

I have never seen, on my drawings, the TCM's actual hookup up.  BUT, on the block Chassis Harness....the power for the shifter and TCM and such comes directly from the FRONT PCB....so, theoretically, power (12 VDC) comes out and goes to the TCM and shifter....then there is a run all the way back to the Tranny and the Output Speed sensor and the Engine Speed sensor (interface).

You may be right....but I would want to verify....Others may know immediately... REAL, as I think on it, CONCERN is to NOT get any stray voltage spikes.  THAT is especially critical, I think, on the J-1939 MPX Data Buss....which runs from the fore to the aft....  THAT is the most sensitive....  and it is hooked up, I think...memory) to the TCM .and I KNOW it is plugged into the ECM.....if Memory is correct...

SO, all the previous precautions apply..that;s why I am skittish...You can see the block diagram below  This is the 12 VDC...but the J-1939 is a bit more complex and I don't even know if I have prints on it...

Chassis Harnesses.pdf

[dennis.mcdonaugh]

I disconnected both sets of batteries and turned off the chassis and house switches in the rear run bay when I had to reweld the hydraulic motor mount on my coach. 

Edited October 27, 2023 by dennis.mcdonaugh

[Ivan K]

3 minutes ago, dennis.mcdonaugh said:

I disconnected both sets of batteries and turned off the chassis and house switches in the rear run bay when I had to reweld the hydraulic motor mount on my coach. 

Funny that this was the exact same reason for my welding. Looks like they did not get that part right back then. I did not want to mess with the ECM, TCM/VIM connectors. Easier said than done where they are. Then there is the ABS and other electronics if one wanted to go to that extent. Welding shop would have no idea so that would be on the owner to do.

[dennis.mcdonaugh]

25 minutes ago, Ivan K said:

Funny that this was the exact same reason for my welding. Looks like they did not get that part right back then. I did not want to mess with the ECM, TCM/VIM connectors. Easier said than done where they are. Then there is the ABS and other electronics if one wanted to go to that extent. Welding shop would have no idea so that would be on the owner to do.

Mine had a short bead down each side of the bracket. I put one on each side and the front and back along the frame rail. 

[timaz996]

This sticker is on my battery compartment door.

[Ivylog]

If you read what Monaco wants disconnected you’ll never weld on your rig. I did read and decided to bolt 2 more receivers on my 04 Dynasty 20 years ago. With more time and research I now stick weld by turning the batteries off and grind a good grounding spot next to where I’m welding.

[dl_racing427]

23 hours ago, timaz996 said:

This sticker is on my battery compartment door.

I stand corected.  That's the decal on my rig as well.
I seemed to recall it said at the tranny.  Thanks for the correction.

[wamcneil]

On 10/27/2023 at 11:08 AM, timaz996 said:

This sticker is on my battery compartment door.

I’d sure be interested to talk to an Allison engineer to understand how a destructive voltage potential could result from welding on the chassis…

Other than welding right up against some wiring, melting through the insulation and arcing directly to a sensor wire, I just can’t imagine how applying a fairly low voltage potential to the frame could possibly generate a voltage potential between the ECM and the chassis. Even if the welder is a complete idiot and has a bad ground, far from the welding location…

I would think that a faulty shore power ground would be far greater risk to the electronics .

In my old body shop days we welded on hundreds of cars and I’m pretty certain the guys never once bothered to disconnect a battery, much less an ECM  

Of course… carelessly starting a fire behind the panel was sometimes a problem. 😞 But never once had a problem with sensitive electronics 

W

[dl_racing427]

18 hours ago, wamcneil said:

I’d sure be interested to talk to an Allison engineer to understand how a destructive voltage potential could result from welding on the chassis…

Other than welding right up against some wiring, melting through the insulation and arcing directly to a sensor wire, I just can’t imagine how applying a fairly low voltage potential to the frame could possibly generate a voltage potential between the ECM and the chassis. Even if the welder is a complete idiot and has a bad ground, far from the welding location…

I would think that a faulty shore power ground would be far greater risk to the electronics .

In my old body shop days we welded on hundreds of cars and I’m pretty certain the guys never once bothered to disconnect a battery, much less an ECM  

Of course… carelessly starting a fire behind the panel was sometimes a problem. 😞 But never once had a problem with sensitive electronics 

W

There are several ways that welding can affect electronics.

First is a ground loop, where high current flowing through the chassis causes a voltage drop.  With electronics that may be connected by other conductors to different spots on the chassis, this voltage could be seen by the circuitry, possibly causing damage.  Disconnecting those other current paths helps ensure this cannot happen.

Second is induced current from welding near conductors.  The magnetic field from the welding cables can induce currents into other circuits.

Third is high frequency energy emitted from the arc itself.  This can also be induced into circuits.

Fourth is the high frequency start on many TIG welders, which increases the risk in number three above.

I'm sure there are other risks, but those are the ones that come to mind.
I do have an electronics and communications background for reference.