What to disconnect and where to find it prior to welding?

ilyafish · December 25, 2008, 03:41:13 PM

I am looking to begin welding new framework early next week. I have read on here that I should disconnect the computer and other things, but i forget exactly what it was, and i have no idea where to find it.

Thanks guys!

rv_safetyman · December 25, 2008, 03:53:05 PM

There was a pretty good thread on this subject a while back: http://www.busconversions.com/bbs/index.php?topic=10086.0

Lots of discussion back and forth. One of the suggestions was to unhook the battery cables and then connect them together (off the battery). I had asked if anyone had tried that, and I don't think I got any good feed back.

Jim

John316 · December 25, 2008, 04:08:36 PM

Yup, all of that is good advice...I wonder why???

God bless,

John

Blacksheep · December 25, 2008, 05:08:17 PM

My DDEC books tells me to simply un-plug the harness from the ECM and to also disconnect the batteries! Didn't say anything about grouping them together though! My ECM is located on the rear center of my 8v-92 on top. The harness plugs are two side by side on the curb side of the ECM. The plugs have a small bolt in the center that is hard to see but you have to loosen it first or your doing nothing!

Ace

John316 · December 25, 2008, 06:43:13 PM

We just disconnected the Tranny computer, engine ECM, and the batteries. (To abbreviate the thread posted above.) Also, if you have house batteries or inverters, make sure you take care of those too.

God bless,

John

ilyafish · December 25, 2008, 07:15:41 PM

John, where is the tranny computer located?

Jriddle · December 25, 2008, 08:39:47 PM

Whatever you disconnect to be safe is a good idea. The main thing when welding is keep the ground close to where you are working. I work in a plant that is computer controlled with plcs. We weld every day with no problems. Electricity will take the shortest path. Keep this in mind when welding. Hook your ground as close to your work as possible.

John

John316 · December 26, 2008, 05:11:17 AM

Quote from: iminaccess on December 25, 2008, 07:15:41 PM
John, where is the tranny computer located?

Ours was on the rear wall, driver side, first bay. I don't know where yours would be, since we have a DL3. If you can't find it, call MCI tech support. They will know (if somebody here doesn't).

HTH

God bless,

John

Chopper Scott · December 26, 2008, 05:51:45 AM

Jriddle has the correct answer. I have a portable service truck that we weld off of and have never experienced any type of computer or alternator problems. In fact in my 30+ years of welding I have never experienced a problem. But it doesn't hurt to take extra precautions. Just keep that ground clamped directly to what you are welding on.

Sammy · December 26, 2008, 06:10:43 AM

Do you have an electronically controlled engine and transmission in your 1981 MC-9?
No disrespect is intended at all, early 9's we had were all mechanical - non DDEC, non ATEC.
If you do, check inside last cargo bay on streetside (L/S) and look up. You'll see a cover with Dzus fasteners, check that. Good luck.

John316 · December 26, 2008, 06:17:28 AM

Quote from: Sammy on December 26, 2008, 06:10:43 AM
Do you have an electronically controlled engine and transmission in your 1981 MC-9?
No disrespect is intended at all, early 9's we had were all mechanical - non DDEC, non ATEC.
If you do, check inside last cargo bay on streetside (L/S) and look up. You'll see a cover with Dzus fasteners, check that. Good luck.

Thanks Sammy, I didn't know what the MCI 9's had. Thanks

God bless,

John

belfert · December 26, 2008, 11:06:01 AM

My Dina says to remove the fuses for the DDEC and WTEC along with removing the ground for the equalizer before welding. I can't find the fuse for the WTEC so I just disconnect the plug from it.

Kwajdiver · December 26, 2008, 03:21:10 PM

Middel bay, driver side,,, crawl in the you will find a panel the length of the bay that will pull down with a little luck and a large screw driver, it will open down. Watch out for all the dust and dirt that will come with it. If you have a ECM it will be located there. Disconnect everything and you should be safe. Along of course with the batteries.

At least that is where mine is....

Or just do what Sammy said.....

MCI-9 83 with a ATEC....

Bill

NewbeeMC9 · December 26, 2008, 07:17:23 PM

I had a buddy that thought the lug nut was a nice convenient place to hook the ground clamp. Welded fine but when he went to take off, he noticed a little extra to overcome and get the truck rolling. Then mile or so down the road the wheel was flopping.

seems the bearing was the highest resistance in the circuit and welded it self together.

It was a lot funnier listening to him tell it but i hope it helps somebody.

Jriddle · December 26, 2008, 09:33:14 PM

Bearings are not a good thing to pass though when welding. All one has to do is just imagine where the electricity has to go through when welding and keep it as close to the work as possible. I have welded on computer controlled curcits that should have been disconnected to keep circuit boards save with no problems. The trick is to know where the path the electricity wants to go and ground to your work. Bearings and circit boards aren't what you want to pass though to complete circit for welding. If you feel better unhooking things. I not going to tell you that that is BS, but you can save a lot by being smart about the flow of your welding circit.

My experience John

What to disconnect and where to find it prior to welding?

Blacksheep