I've got an old MillerMatic 35 mig welder and I've heard you can wire weld aluminum by adding a a spoolgun and using 100% Argon.
I'm confused about using a D/C welder to weld an A/C process....
I have a tig but need to make some LONG runs for a project and figure a wire welder would be nice.

Any welding smart people out there?

Nothing to be confused about. It works on DC. They work well in certain applications. Get your aluminum clean preferably with new stuff(wire brush, flapper). We weld aluminum tubing to cast aluminum and the spool gun works great for the job.



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Yeah that's one thing EVERYBODY says ..... Stainless steel brush the crap out of the aluminum and then wipe it down with a chemical of some sort.....
Any suggestions on a spool gun size/brand? Any you know of NOT to buy?

I tried to get spool gun for my old millermatic and found out cost of gun was just barley lower than a new welder and with the spool gun. Good luck.1500 for gun and 1700 for both.

Used my 251 only once to build a hitch for one of the trucks. I use the little one in the back all the time. 251 is up for sale. I came across a deal for a Miller Diversion 180 complete almost new, for 1K.. Can't pass it up

This message has been edited. Last edited by: TD3550,

I have an old miller spoolmatic 3 with the 14 pin connector , i think it runs off 24 volts. My welder is a 251 with the 10 pin connector . For some reason the local miller store can't find the right psa adapter to make them work together.

It's been a while since I have used a 35 and do not remember what kind of plug if any on the front of the machine for a spoolgun. You can run aluminum wire through your gun and hose assembly and it will weld but feeding can be iffy if you are not careful. Liners made of plastic can be installed to help the feeding of aluminum wire. I would recommend using the largest wire (3/64). 5356 may feed a little better because it is more stiff but I generally recommend 4043 works for all around applications. Good Luck.

My MM-35 must have been made before they put multi-pin plugs in the front panel...I was just going to get a universal spool gun and wire it as needed to interact with the welder...Should just be splicing into the trigger wires and disabling the steel spool feed....
I was hoping someone here had done this and was happy with the results..

All spoolguns need power to run. The old mig welders don’t have the proper circuitry to run an external spoolgun. Miller made separate boxes called WC 24 or WC 115 to run external spoolguns. All newer machines have the necessary circuitry and direct plug. They sell/sold many machines with a spool gun tossed in for free. Flip a switch and your welding aluminum or steel. Anyone comes to me with a request like this and I tell them buy something newer. I am a Miller certified repair shop and have been for 20+ years. Old MM’s were good machines but limited in what they can do. I have wired up some oddball stuff over the years but never even attempted to make this work. A MM 35 is ancient !

This message has been edited. Last edited by: SCDIV1,

My MM35 is ancient because it didn't die early. It's a xlnt solid machine that does nothing except lay down good looking strong welds.
If a spool gun plugs into the high voltage out and I wire in a trigger switch to the existing circuit what wouldn't work? In theory the welder doesn't know or care where the wire is feeding from. Correct?
Obviously you know your business so I'm not arguing with you, just asking questions because you'd know the answers....

The spoolgun needs the correct AC voltage it requires to operate. The weld voltage is DC and not correct. The spoolgun needs power to run its motor. It also must close the circuit on the MM35 that powers the contactor. A WC stands for Weld Control and it was used on older machines for this purpose. They made a 24 volt and a 115 volt. It’s all old stuff, not available. I don’t recall if that was even a viable thing to make work. You asked for some info and did not like the answer. If you came into my shop or went to a Welding supply place that sold machines, you’d get the same answers. Old machines that still work are fine, but limited in what you can do with them. And I will add that trying to feed aluminum wire thru a std type gun with 10-15’ of cable is very unlikely. Aluminum wire is very soft and will not make it thru without problems. They make Push-Pull guns for that purpose. Very expensive and again won’t work with an old machine.

This message has been edited. Last edited by: SCDIV1,

Please don't get pissy about this bro....If you read my op and then the 2nd post you'll see I kinda agree with you. Doesn't mean I didn't like your answer. It means I'm still confused about how a D/C machine can A/C weld....
As you noted, I tried the feeding aluminum wire through my existing gun and quickly found out that isn't going to happen....I then found several sites explaining how to install a spool gun on a MM35....BUT nobody is addressing the A/C-D/C deal...Except the 2nd post here of course...
I welcome your input BECAUSE you're saying exactly what I'm wondering...but I don't want your help if it aggravates you...

A Miller 3035 spoolmate gun and an SGA-100 adapter box. Over $1000 new for those 2 items. SGA-100 is a stand alone device that should allow you to use your MM35. The spoolgun is the lowest cost unit Miller makes and is $685. The SGA-100 is nearly $400. My place does not sell machines so I got this info reading thru some Miller pages on machines and compatibility to what works with what. There ya go...

The welding output of a MIG welder is DC. AC is usually used for the TIG process for aluminum. Aluminum MIG will remain DC.

Mig welders are DC output...

Polarity can be changed to suit various wire and with or without gas.

Tig welding steel uses DC output
Tig Welding Aluminum uses AC output


DC is way smoother.....BUT it does not work well on Aluminum for Tig welding


Aluminum oxidizes as your welding

AC helps to reduce the oxidation and adjusting the AC wave balance can either give you more cleaning or more penetration by going more positive or less positive.


Modern machines have way more adjustability....and pulsers that can also help make a nice weld


Lincoln engine drives are big generators.....pure DC output. Old guys love those machines for stick welding...

Miller engine drives have always been alternators.....they produce AC and its rectified to DC...not quite as good if you ask some welders that have used both.


Everyone is pushing Inverter based machines......Fantastic welding and adjustability.....Light, lots of power out with less input needed.


Drawbacks....expensive.....never going to last as long as old transformer based machines.....parts are way expensive and makes it likely some machines will just get scrapped and replaced...…



I just fixed a Lincoln Ranger 250 a couple weeks ago....mid sized engine driven machine.


They were kind of early versions of an inverter type machines. Machine was built in 2004 and had about 600hrs on it.....


Control board failed...…$1500+ for the Board.....No alternative.....Repair of old board not possible.


A new machine is about $4000..Repair was $1800 and the guy needed it ASAP...and was happy to have it back in a few days.....


Back to work......Just repaired a 7KW gas Onan and back in it goes.....