Welcome to Jon's Jeep
Portable Welder Plans Page...

During the Christmas holidays, while I was visiting my parents, I got to reading the YJ FAQ (it has a lot of information in it relevant to CJ's as well). The first question in the FAQ is regarding using the alternator in the Jeep as a welder. While I'm pretty sure this is possible, and I'm planning on doing it myself fairly soon, the answer given is not at all clear on exactly how it's done.

My dad recalled a photocopy of an old Mother Earth News article that described in detail how to build a portable DC arc welder using a car alternator, so he dug it up. We took an afternoon and built the welder, and it was very cool to actually weld using something we put together that quickly (and cheaply).

The Welder Plans

Basically, what you need is the following:

  1. car or truck alternator, preferably without a built-in voltage regulator (although you can use one with a built-in regulator, you have to bypass it)
  2. motor or engine
  3. car battery
  4. platform to mount everything on
  5. on/off switch
  6. big diode
  7. thermal overload switch
  8. one or two 1.5 ohm 8 amp resistors (you may not need these if your motor is powerful enought - we needed them with a 1 HP electric motor)
  9. a couple feet of #18 wire, and a couple feet of heavy (1/0) wire
  10. old pair of jumper cables
  11. bunch of connectors/stak-ons

For a platform, you could use an old lawnmower, and thus also be supplied with an engine and a place to mount the battery & alternator. We used a chunk of plywood, with a few pieces of angle-iron to mount everything to.

For the alternator, we used a regular 66 amp alternator, the kind with a built-in regulator. We took the regulator out, and bypassed it, grounding the brush it was connected to.


Wired as above, you get a reverse-polarity DC welder, which is standard. To get a positive polarity welder, just switch the ground-clamp with the rod holder.

We used the jumper cables as our welding leads, and drilled a couple small holes in the end of one of the clamps to act as a simple rod holder. After we got it working, and laid our first bead, we "machined" a new custom rod holder using a chunk of 1/2" steel and a piece of pipe. Cut to shape, drill a few holes, tap some threads, weld it together, and you get a nice (cheap) rod holder.

I hope you find this useful. When I get my on-board welder project done (due to start in February, immediately following my on-board air project), I will provide full specifications and plans and pictures of what I have done.

Go back to my Jeep page.