Welder

Onboard Welder

Facts are facts...if you wheel on tough trails, eventually you will break something. Even if it's not on your vehicle, somebody still ends up getting stuck. With that fact in mind, I decided to add an onboard welder setup to my TJ. Additionally, since I don't have a home welder setup, I figured I could use the welder for fabrication work as well.

I looked at the two major brands (MobiWeld and Premier Power Welders) on the market and found that both were well liked by customers and both did an excellent job of field repairs. But, when I looked a bit further, I realized that only one met my needs for several reasons. You see, first of all the onboard welders require you to swap in a different alternator...no problem for most folks, but with my York air compressor, I simply didn't have the room for the larger Premier unit. Also, I liked the fact that the MobiWeld unit is 100% solid state. There are no solenoids to stick, etc. The MobiWeld unit also has a built in limp-home feature that lets the alternator work easily even if the welder box fails. Another plus of the MobiWeld is that you don't have to switch from "power" to "weld" like the Premier unit. With theMobiWeld, I can use the power outlet to run lights, grinders, etc, and then strike an arc without ever switching modes. I can also rapid recharge batteries if necessary...great for winching! This would be extremely useful for welding under the vehicle on the trail...just use a trouble light and an auto darkening welding shade, and when the arc is struck the shade darkens and power is diverted from the light to the arc. When the arc is released, power goes back to the light and the shade lightens. Finally, I liked the smaller size and simplicity of the MobiWeld box.

Initially, I just ordered the alternator....I didn't have the funds for the entire rig, but I wanted to be welder ready when I had the cash to buy the rest of the unit. So, I called up MobiWeld and ordered the 160 amp unit. The 160 amp rating is actually an equivalent welding rating...the actual alternator is a standard 100 amp Bosch unit that bolts right in to the TJ with no mods required to the factory bracketry. It uses over the counter Bosch parts, but has some internal modifications to make it work better as a welder. These mods include larger diodes that can take the extra power the alternator needs to produce for welding as well as converting the stator from a Y configuration (star) to a Delta configuration (triangle). Delta wound stators are the standard for most big rig alternators and produce a 34% increase in amperage over the Y configuration simply by changing the order three wires are connected inside the alternator. The unit is hot rated, so it delivers 134 amps (100 plus 34%) even when hot. Premier's cold rated alternators lose about 20% of their power when hot. Also, unlike the Premier unit, it is not a "hopped up" unit, so it doesn't build up heat which will eventually kill an alternator. Nothing on the unit is customer serviceable except the regulator, which incidentally is a stock Bosch or Wagner part...you can get them anywhere. I installed the alternator, and then about a month later added the welder unit. For simplicity, I've taken the liberty of wrting it up as if I did everything at once.

The unit arrived well package and with excellent generic instructions as well as model specific instructions. Here's what was included:

Modified Bosch 100 amp alternator (Chrysler form factor)

Heavy duty resistor (simulates stock alternator load to prevent "Check Engine" light illumination)

MobiWeld unit with mounting bracket

Rectifier

Hand throttle with mount (I didn't use these as I already have a hand throttle)

Heavy duty resistor (simulates "Generator" light load)

Tweco stinger, battery clamp, and welding leads

Relay

Plug adapter (unit has a European outlet)

Assorted small hardware

Generic and model specific instructions

Here's a picture of the parts and one of the alternator. The alternator on the right is the Bosch unit, the other unit is the stock Nippondenso unit. The pulley has already been swapped over in this shot. Notice the large cooling fan and heavier construction of the Bosch. Also notice the electrical pigtail on the Bosch...it connects to the welder unit and is used for switching and excitation of the alternator:

I used the following tools to complete the install:

3/8" electric drill and bits

Screwdrivers

3/8" ratchet and sockets

Multimeter

Electrical crimper

Here are the steps I followed. The instructions were good and I had excellent support from Scott at MobiWeld.

1. Remove the serpentine belt. Loosen the hold down screw, then loosen the adjuster until the belt is easy to slip off the pulleys.

2. Disconnect the battery.

3. Remove the alternator. Remove the power and ground leads and the field harness. Remove the two mounting bolts. In my case, I had to first remove the York compressor and brackets as well.

4. Use the drill to enlarge the lower mount hole in the new alternator to accommodate the stock bolt.

5. Swap the pulley from the old alternator to the new alternator. Use the supplied washers to shim the pulley into the correct fore-aft position so it lines up with the factory pulleys.

6. Install the new alternator using the stock hardware, but only connect the ground cable.

7. Install the small heavy duty resistor between the terminals of the generator field harness to simulate the stock alternator load. I soldered this in place, then taped over it to prevent moisture intrusion.

8. Choose a location to mount the MobiWeld power box. Most folks mount them on the passenger side fender, but in my case, that area is occupied by the York compressor. I chose to mount the box vertically under the brake booster, on top of the ABS tray. I cut a large hole in the tray to allow the cables to pass through. I also cut the stock bracket and re-shaped it so I could bolt the box to the fender to prevent it from moving.

Here are two detail shots of the power box in its mounting location. The first is viewed from the driver's side fender. Notice the simple layout of the controls...the large blue cover on the left is the power outlet. In the center are the LEDs that indicate the status of the unit. Next to the LEDs are the welder cable outlets. On the right is the mode switch which allows the unit to function in Normal mode (charging) or Power mode (welding and 115 volt DC power). The reshaped bracket is not installed yet, but ties to the fender just forward of the box. The second shot is viewed from the driver's side of the grill, looking aft:

9. Select a location for the rectifier. I chose to mount mine on the fender just ahead of the power box (sorry, no picture yet).

10. Route the cables. I ran all the cables down through the hole I cut in the ABS tray, then ran the two large cables, the charging lead, the yellow and blue wires, and the 4-wire cable over the top edge of the firewall (with the stock harness) and ran the small red cables directly to the rectifier. I connected the power lead and the ground (the two large cables) to the back of the alternator in the locations previously used by the stock wiring. The 4-wire cable connects to the plastic connector that is attached to the alternator. The charging lead connects to the stock power lead at one end and to the rectifier at the other end.

11. The yellow and blue wires were connected to the large resistor (simulating the generator light) and then to an ignition hot lead from the stock wiring. Initially, I connected them direct to a wire from the PCM (computer) that excites the factory fuse box. This connection didn't work well, causing the alternator voltage to be too high since the regulator was sensing low voltage (PCM output voltages are 12V). To rectify this problem, I installed a relay in the factory power distribution box under the hood. I used the same PCM wire as a sense line and used direct battery voltage to connect to the yellow and blue wires. That way, the regulator sees true battery voltage, eliminating the over-voltage condition.

Here's a detail shot of the relay installed in the factory power distribution box. The near relay in the center column is for the York compressor clutch, while the far relay is for the MobiWeld. This is viewed from the left front fender:

12. Reconnect the battery.

13. Reinstall the serpentine belt. Installation is the reverse of removal.

Overall, my impression is that this is a excellent unit. It came with all the necessary pieces to install a working welder. The instructions were good and the telephone tech support was exceptional. As far as I know this was one of the first installations on a TJ. Scott walked me though the installation, helped me troubleshoot, and even called me back a few weeks later to see if I was still satisfied.

So...how does it work? It works extremely well. To weld, I simply switch the mode selector to Power, use the hand throttle to set the engine speed at about 2,500 RPM, and start welding. Since I'm a novice welder, I had my friend and fellow club member John Donovan test it out and give me a few quick lessons. John is an experienced welder who has both stick and MIG units in his garage as well as a plasma cutter and Oxy-Acetylene torch. His overall impression was that it was the easiest stick welder he had ever used. In about 1/2 hour, I was welding strong clean welds like an experienced hobbyist welder. The welds come out very clean since the high frequecny of the unit agitates the impurities to the surface of the weld. I haven't had a chance to do any trail repairs, but I know when I need it, it will perform like a champ.