Lincoln Weldpak Spool gun fitting

Greetings folks,

I have a Lincoln 175HD, and after birdsnesting till I wanted to throw the thing out the shop door, I decided to get a spool gun. Unfortunately, I didn't realize that the one the welding shop told me I needed, wasn't going to work with my welder. I didn't have the correct plug on the welder to fit the spool gun, and found this thread in efforts to find a fix. It all seemed so complicated to me, so I came up with a different solution that worked excellent, and I think anyone can do with stuff in their shop and the parts supplied with the 100 series spool gun from lincoln. So, let me explain what I did step by step, in case someone wants a different solution that is a little more simple, and can use parts on hand. Forgive me if maybe I'm being a little nieve on some of this, but I've tried this set up, and it has worked great so far.

So, I started out with opening up the cabinet, and after reviewing the wiring diagram, found that pin 2 (541 connector)on the 10 pin molex connector going into the main board is the + DC voltage going to the wire feed motor, and pin 8 (539) is the negative side. I decided to use the switch supplied in the SG100 spool gun package to switch from the cabinet spool motor, to the spool gun motor, depending on which one I wanted to use. I started out by drilling a hole inside the cabinet, from the wire feed side in order to fit the switch boss. There is a stamped ground mark inside the cabinet you can use for location reference. I drilled just to the left of this mark when viewing from inside the cabinet where the transformers are located.

On the pictures in the last post, you can see a small hole just below and to the left of the big hole you just drilled when viewing from the wirefeed side. I drilled this hole just a little larger with a step drill, in order to fit a rubber grommet and a pair of wires that will feed the motor on the spool gun eventually. Easy Peezy.

I then mounted the switch from the transformer side, fitting the switch boss through the hole in order to fasten the lock nut on from the wire feed side. I preferred to position the switch vertical, so that the toggle switch on the inside flips up and down as opposed to side to side in order to help me remember what is connected.

Now comes the critical part. I identified the positive and negative wires coming from the 10 pin molex connector going down to the wire feed motor on the welder. It is easy to find if you follow the motor leads starting from the lower R corner of the cabinet when viewing from the transformer side, and tracing the wires up, see the picture. You will then clip them both, yes the positive and the negative wires going to the motor. Make sure and leave enough length that you can put on a female spade connector on each wire and connect the positive lead to the left middle post on the switch, and the negative to the right middle post. This is the input variable voltage coming from the main board to the feed motor, and is how you will switch from the cabinet motor, or to the spool gun motor. Be specific about where you connect these wires, positive (grey wire) to the middle left post, negative (white wire) to the right middle post.

Now, break out your soldering gun and heat shrink tubing, and do this step right. Take some extra stranded wire you have laying around (22 gauge up to 16 gauge will work) and prepare to lengthen the wires going down to the wire feed motor so you can attach them to the lower poles of the toggle switch. I like to use black for the negative side, and red or something close for the positive side to help cut down my chances of screwing up and having the motor run backwards. This is DC, so it matters. This is important. The positive lead from the cabinet feed motor (grey wire initially, after you add a length of red wire, it is now red) goes to the left bottom pole of the switch, viewing from the back of the switch. The negative wire from the cabinet motor (white wire initially, now that you've added a length of black, it's the black wire) goes to the lower right pole of the switch. If you want to test your welder and make sure you didn't screw something up, now is a good time to make sure your drive motor is going in the right direction. You need to make sure the molex connector is connected to the main board, and that the switch lever is in the "up" position for the contacts to close. Plug the welder in, and pull the trigger on the long liner gun (assuming you haven't unplugged the switch from inside the cabinet yet). You should find the feed motor spinning normally in the forward direction. If the motor does something different, check your wires. Flip the toggle switch lever into the down position, and you'll hear gas flowing, but the feed motor will no longer function, as expected.

Next, take another 10 inches of red and black wire, and feed it through the small hole you put a rubber grommet in earlier. Fasten female spade connectors to the ends of the wire on the transformer side, and connect to the switch as follows. The red wire goes to the top left pole of the switch, and the black wire goes to the top right pole of the switch. Once these are connected, pull the excess wire through the hole in the cabinet until it looks nice, leaving extra wire hanging out of the spool side of the cabinet. Because I'm an idiot, I took a black permanent marker and wrote on my cabinet which direction I need to flip the toggle lever to get the wire feed motor I want. I used female spade connectors on the ends of the spool gun motor wires on the spool side of the cabinet to prevent myself from plugging in the trigger wires by accident. Notice that the stock gun trigger connectors are male spade connectors. You don't want the spool gun motor wire ends to be male too, or you might get them crossed when you switch guns (having all female plug ends). These wires are what will control the new SG100 spool gun motor.

Now is definitely the point of no return. I missed taking pictures of this step, but it's easy. Cut off the 4 pin wired screw connector from the end of the spool gun hose that goes into your welder cabinet. It has four pins, a barrel screw lock, and a black sheath of about 6 inches long or so. This is where the 4 wires that control your spool gun are bundled together. Once you cut off the connector and peel the heat sheath back, you will identify 4 wires. You will see 2 white wires, a red, and a black. You guessed it, the red wire is the positive DC wire feeding the spool gun motor, and the black is the negative. These wires are smaller than expected, maybe even 22 gauge. Use your soldering gun, and heat shrink tubing to add about a foot of length to these wires. You will cut the excess off. Make sure you solder the red to the red, and black to the black so that you can easily remember and connect them to the right wires in your cabinet. Next, add about a foot to both of the white wires. The white wires coming from the spool gun are the trigger switch wires. It doesn't matter whether your positive or negative here because the circuit is normally open, and pulling the trigger on the gun simply closes the circuit. Once you've added length to these four wires, bundle them together and heat shrink the whole bundle. I used 1/4" diameter heat shrink because the wires I used to lengthen them were larger in diameter, probably 16 gauge.

Now, swapp the old long liner standard gun out, and install your new SG100 spool gun in to the welder socket. Feed the 4 wire bundle into the welder compartment, up through the plastic ring, and admire your work. Now, the two white trigger switch wires will simply connect to the original gun trigger control spade connectors in the cabinet just like the old gun did. Use female spade connectors for each of these wires, and plug them in.

Next, cut your too long red and black wires from the spool gun until they make sense and fit nicely in your cabinet. Add Male spade connectors to each of these wires, and plug the red spool gun wire into the red wire coming through the chassis from the toggle switch. Lastly, connect your black wire to the remaining black wire coming from the switch. That should do it.

Well, plug that baby in and test it out. Make sure to not pull the trigger on any gun while changing the toggle switch position, no need to stress out any circuitry. Change the spool speed pot on the welder, and you'll be pleasantly surprised that it controls the speed well for either feed motor. I did notice after welding some aluminum, that the spool gun motor speed is faster than the cabinet motor speed in any given adjustment on the pot. I actually like this because I ran into times where the wire wouldn't feed fast enough in some circumstances. If you think the wire speed adjustment on the spool gun isn't sensitive or fine enough, you could always add another pot inline. I'm happy with it. Very simple, use the switch that comes with the new Lincoln spool gun, add some wire and spade connectors, drill a couple holes, and you easily can switch out either gun by flipping the toggle switch. It is easy enough to unplug the spade connectors for the spool gun, you don't have any visible switches on your welder, and it looks factory. This was a more simple way for me to accomplish the task of adapting the Lincoln magnum 100SG spool gun to my 175HD mig welder. It tested out fine, and other than me being a rookie at welding aluminum, it should work out well. If something blows up, I'll let you all know. These two pictures show a repair on an aluminum cabinet I did tonight, and severe over-penetration on the inside. Im still screwing around with the adjustments.....

I hope this will make it a little easier for the next guy, and not to be afraid of adding a spool gun to this excellent welder. If you don't like the 100SG gun, you can easily adapt in another gun with this method. Good luck!!

Thanks very much for posting that, some very useful information.
I split it from that other thread as it's worthy of it's own and will make it easier for people to find.
Welcome to the forum.

No problem on splitting the thread, thanks for doing that. Thanks for having this forum to help people out, and happy welding


Duhfactor