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Welding on computer controlled cars?

Kern Dog

Life is full of turns. Build your car to handle.
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I thought I recall reading that welding on computer controlled cars could result in computer or sensor damage....YET I've seen muffler Monkeys do muffler installations and weld without disconnecting the battery.
I mention this because I need to weld a cracked pipe and wonder if this was a BS rumor about computer damage.
I can disconnect the battery but am I over-thinking this?
2007 Ram 1.jpg

I can't believe this 360,000 mile Flowmaster muffler failed so soon. The flange at the inlet just cracked and broke last week. Whatever happened to American quality ?? :poke:

I had this muffler and tailpipe set on THIS 2006 Ram before....
06.JPG

A trip through san Jose on a mid November day in 2007 when a guy ran a stop sign....

2006 1.JPG
2006 7.JPG

Before the tow truck came to get this truck, I pulled the 30,000 mile exhaust off and installed it on the 2007 Red truck...I've racked up 330,000 miles on the red one!
 
You need to make sure the ground for the welder is near what you are welding, and in the same electrical path. If welding the exhaust, ground to the exhaust, not the body or chassis.
 
A trip through san Jose on a mid November day in 2007 when a guy ran a stop sign....

View attachment 780766 View attachment 780767
Before the tow truck came to get this truck, I pulled the 30,000 mile exhaust off and installed it on the 2007 Red truck...I've racked up 330,000 miles on the red one!
Oh damn man, OUCH!!
I love these late-model Rams. They're really good trucks and tough as heck.
I was sort of saddened by the 2009-up ones, not because of the wonderful new IRS that came with them,
but because the newer design construction felt flimsy in comparison to the 2002-2008 ones, at least in
the sheetmetal.
BTW, I'd love to have gotten those 20" rims off the carnage to replace my original "petal" ones on my 2004.
Mine are looking sort of nasty anymore as the chrome cladding erodes...
 
451Mopar is correct, ground clamp close to your work as possible on the same piece that you're welding on.

Just think about the current travel, it will take the path of least resistance.

Example:
If you would clamp your ground on the frame of the car and weld on the rear end housing, the current will travel through the bushings on the spring hangers, possibly the axel or gear bearings and arcing through them, causing damage. The same thing can happen with electrical components if you let them become part of the current's path.
 
You can also pick up transient voltage through all of the sheet metal, frame, etc that is not isolated from the battery ground circuit. Keeping the weld ground close to the weld will help but there is still some risk. We have to isolate weigh scales when welding platforms for example as the electronics are known to be affected and often fail after welding.
 
Yes on all of the above.....That said I have welded on many computer controlled cars/trucks with no issues. BUT...never say never. disconnecting the batt is easy on your truck, its not always easy on everything . again I have welded on many cars with no issue sooooo give it your best shot batman
 
I used to believe a battery disconnect was enough but about 15 years ago I welded in a cage and did not disconnect
the ECU. The next event the ECU would run but ran full rich after 4K RPMs. I always unplug the ECU now regardless
of the amount of welding. Lesson learned for me.
 
Just to be on the safe side, in addition to pulling the battery cable, I'd also unplug the PCM/ECU.
 
The controllers are all tested for transient suppression and voltage load dumps and can usually withstand welding transients, but component tolerance vary so I personally would disconnect the modules before welding. Also dirty grounds don't help either.
 
as a double master A.S.E tech gm ford Chrysler all tell you to disconnect the negative battery cable BEFORE welding. This is slandered practice when welding. ever had an ignition box go out 5 to 10 days after and wondered why ? i have seen an m.s.d box go bad 3 passes after a weld in the pits that a guy had welded his car and poof. so go and do what you gone do hope for the best.
 
I had an employee use a plasma cutter on a chevy cobalt and fried every ******* module..... he had the battery disconnected both sides......... that was the last time we plasma cut anything late model
 
an anti zap battery isolator helps "sometimes" too
we used them a lot when working on aerial equipment/cranes
in/on modern computer controlled stuff
back in the late 90's early 2000's
worked most the time

time was money, especially in the repair/service side of stuff
people didn't want to pay a bunch for
techs taking/unplugging electronics,
when it wasn't part of moist repairs or bid costs either,
make a simple/quick job $100-$500 repair
a $1000-$2000+ easily otherwise,
to add that in labor, dealing with all of that,
isn't gonna' go over well or work for most shops or paying customers

Welding Battery protection -Anti-Zap Auto Surge Protector -12vt.jpg


we'd disconnect the battery prior,
but it didn't always keep **** safe

make sure the ground is close to your work
& on the piece you are welding on, better yet

todays electronics are so sensitive, fragile
better to be safe than sorry

if you're worried, unplugging everything that has a sensor,
or that's computer controlled, that's close to where you're working
or stuff that goes to ground close to where you are welding
or disconnect it all if need be

good luck
 
Last edited:
UPDATE!

I did disconnect the battery. The terminals were gunked up so I cleaned them up nicely.
I took the advice and put the ground cable about 16: from the point that I was welding. Once I was done, I took the cable off and was amazed at how cool it was. All the times I have welded with the ground cable too far away have left me with a warm or hot cable. I don't recall being told this in my ONE week welding course back in 1988 but it sure makes sense.
The truck is all quiet again, no issues with the computer, the radio presets somehow never got lost but I did have to reset the clock. Oddly, I was done around noon so I didn't have to adjust the clock too far!
Thanks for the help.
 
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