The Mobi-Arc onboard welder is made by Mobi-Power.   They make different units depending on what size and output alternator you have, for our application they sent us a Mobi-Arc 200x unit that can handle up to 200 amps.


To read the installation instructions click HERE.

To read the instructions to convert your alternator click HERE.


The Mobi-Arc had the middle sized box of the three installed welders measuring about 5.25" x 3 " x 4.60".   

Although you can use the Mobi-Arc with your stock vehicle alternator, we wanted to see the difference between a stock alternator and a high output alternator.   

We contacted Wrangler Northwest Power Products and got a 160 amp alternator to go with the Mobi-Arc unit.

Because of poor weather, we had to move indoors for the installs.

The package came with all the pieces necessary to modify the factory alternator over so it could be used for welding.   

Most alternators today are internally regulated.  This means that the voltage output is controled by a voltage regulator that is inside the alternator.   The kit included parts so that you can remove the internal voltage regulator and put the stock alternator back together.

The Mobi-Arc control box will not control the output of the factory alternator.   In the unlikely event of a malfunction, the kit included a bypass plug to bypass the welding circutry and only control the alternator to keep your battery charged.

The truck we were doing the install on is a 2000 Tacoma with the 2.7 4cyl motor.

The alternator was removed (already done in this picture) so that it could be prepared and hooked up to the Mobi-Arc control box.

The instrucions on how to convert the factory alternator were good, the process was simple to complete and should take only a few minutes.

The alternators internal voltage regulator (yellow arrow) was replaced with the new piece (green outline) that would let the alternator be controled by the Mobi-Arc unit.

Note that the old piece had an oval shaped plug, while the new piece has a round plug.

Most factory toyota regulators are set with a single voltage setpoint which gets in the way of MOobi-Arc's pulse-width modulation regulator.   By removing the internal regulator and controlling voltage externally, optimum arc-striking voltage can be achieved.   While the control unit is present, voltage and current are adjusted around 100,000 times per second.   

Should the Mobi-Arc control unit be removed, an external regulator is provided as part of
a bypass configuration.

The rear cover had to be slightly modified to allow for the new round plug to fit properly.. (yellow arrow)

After you modify the alternator by enlarging the hole there is no going back to stock!   If you are under warranty and the alternator fails, the dealership will not replace it as they will be able to see that it was modified.

Using a grinder, the hole was rounded out.
The first try worked, but didnt account for the clip on the side of the plug!   Another quick shot of the grinder and all was well!
Here you can see the rear cover in place with the new plug attached for a test fit.

This is where we ran into the only problem, a problem with both the Mobi-Arc and the Premier Power Welder.

The wiring diagram called for the ignition wire from the old alternator (red arrow) wiring harness to be hooked to the violet colored wire on the Mobi-Arc control unit.   They did not however tell us what color of the three wires present that this was!

The instructions said that instead of hooking up to the ignition wire from the alternator, the other choice would be to hook it to any source that had key on/off power.


  The three wires are white, yellow and red.  As it turns out, the red wire is the ignition wire.   

Of the other two wires, the yellow wire is for the check alternator / battery dummy light on the dash, the white wire is an excite input to get the alternator started initally.   Both of these wires are no longer needed.

With this setup, you loose the check alternator / battery light on the dash, an issue that we will address later.

The next step was to make a mounting bracket for the control unit.   A piece of flat stock was bent and drilled to use existing bolts.
During a test fit, one of the leads was plugged in to check that there would be enough clearance for everything.
A shot looking down showing the bracket with the Mobi-Arc mounting plate already bolted up.
The bracket was painted and allowed to dry before being re-installed on the truck.
With the unit mounted, the next step was to connect all the wires.   While connecting the wires was simple, the wiring harness that came with the unit was much too long for our needs.
The backup voltage regulator was mounted on the underside of the mounting bracket.   In case of a malfunction of the Mobi-Arc unit, you can bypass it and use the backup voltage regulator so that you still have a working alternator and charging system.
Here you can see a shot of the rear of the unit.   All wiring can be easily detached so you can remove the control unit.
The wires were now shortened to the length we needed for the installation.
Once the wires were shortened, everything was hooked up and the electrical checks were performed.
For the throttle control, the control cable was attached to exsisting pulley for the crusie control.   The new cable was clamped to the crusie control cable.
The throttle adjusting lever was attached to one of the air intake clamps.

The Mobi-Arc welder wants you to set your RPM in a specific range to weld.   With the throttle control under the hood and the tach on the dash inside, this can take a few adjustments.

Dick Foster had this slick idea, he mounted a small tach under the hood so he can see what his RPM are at when he adjusts the throttle for his Mobi-Arc Welder.

When the engine is running and Ignition light and the Charge light are illuminated.
When you strike the arc and start welding, the Mobi-Arc switches into weld mode and you can weld.
In Weld mode, the Ignition and Weld lights are illuminated.
Here you can see the difference between the stock alternator (rear) and Northwest Power Products alternator front.   The new Northwest alternator is rated at 160 amps.
While the new alternator is slightly larger, the biggest difference is the pulley size.
The new alternator bolted right in using all existing bracketry.   

The one thing that you need to know before you start the installation of the new alternator is that due to the larger pulley size, the stock belt is now too small.   The stock belt measured 34 3/8th inches.   We first tried a 36 inch belt and it was too long, there was no room to add tension.   We then went with a 35 inch belt and it was perfect.   The alternator belt is the rear most belt on the 4cyl engine, so you have to remove the other belts to get this one on.   

Once the new belt is on, you can adjust the tension and attach the wiring.

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