Chicago Electric 54878 Assembly and User manual

MIG-100 WELDER
WITH THERMAL OVERLOAD
Model 54878
ASSEMBLY AND OPERATION INSTRUCTIONS
Due to continuing improvements, actual product may differ slightly from the product described herein.
®
3491 Mission Oaks Blvd., Camarillo, CA 93011
Visit our website at: http://www.harborfreight.com
TO PREVENT SERIOUS INJURY, READ AND UNDERSTAND
ALL WARNINGS AND INSTRUCTIONS BEFORE USE.
Copyright©2007 by Harbor Freight Tools®. All rights reserved. No portion of this manual
or any artwork contained herein may be reproduced in any shape or form without the
express written consent of Harbor Freight Tools.
For technical questions or replacement parts, please call 1-800-444-3353.
(Manual revised 03/07)

Page 2SKU 54878 For technical questions, please call 1-800-444-3353.
Specifications
Welding Current
.8 mm wire on 16
ga. sheet steel
104.3/95.5 Amps
(Maximum/Minimum Setting)
.8 mm wire on 1/4”
steel plate
103.7/103.1 Amps
(Maximum/Minimum Setting)
Duty Cycle 10% @ 90 Amps (Maximum Setting) or
10% @ 80 Amps (Minimum Setting, actual 11%)
Power Consump-
tion 120 VAC, 24 Amps
Ground Cable 4 AWG, single insulation, 6 foot
Torch Power Cable 8 AWG, single insulation, 6 foot
Power Cord 3-wire, double insulated, 14 AWG, UL Listed
Power Cord Plug UL Listed
Thermal Overload Both settings: 10 min. shutdown, 3 min. back on with Light
Welder Tip 0.030”; Spare: Welder Tip 0.035”;
Will also accept a 0.023” welder tip (not included)
Wire Size 0.030” flux core wire (when using 0.030” Welder Tip)
Wire Spool Size 4” diameter
Overall Dimensions 14-1/2” (L) x 7-7/8” (W) x 15-1/2” (H)
Weight 34.45 lb.
Accessories Spare Welder Tip (0.035”)
Save This Manual
You will need the manual for the safety warnings and precautions, assembly instructions,
operating and maintenance procedures, parts list and diagram. Keep your invoice with this
manual. Write the invoice number on the inside of the front cover. Keep the manual and
invoice in a safe and dry place for future reference.
Safety Warnings and Precautions
WARNING: When using tool, basic safety precautions should always be followed to
reduce the risk of personal injury and damage to equipment.
Read all instructions before using this tool!
1. Keep work area clean. Cluttered areas invite injuries.
2. Observe work area conditions. Do not use machines or power tools in damp or wet
locations. Don’t expose to rain. Keep work area well lighted. Do not use electrically
powered tools in the presence of flammable gases or liquids.
3. Keep children away. Children must never be allowed in the work area. Do not let them
handle machines, tools, or extension cords.
4. Store idle equipment. When not in use, tools must be stored in a dry location to inhibit
rust. Always lock up tools and keep out of reach of children.
5. Do not force tool. It will do the job better and more safely at the rate for which it was
intended. Do not use inappropriate attachments in an attempt to exceed the tool
capacity.

Page 3SKU 54878 For technical questions, please call 1-800-444-3353.
6. Use the right tool for the job. Do not attempt to force a small tool or attachment to do
the work of a larger industrial tool. There are certain applications for which this tool was
designed. Do not modify this tool and do not use this tool for a purpose for which it was
not intended.
7. Dress properly. Do not wear loose clothing or jewelry as they can be caught in
moving parts. Protective, electrically nonconductive clothes and nonskid footwear are
recommended when working. Wear restrictive hair covering to contain long hair.
8. Use eye and ear protection. Always wear ANSI-approved, arc-shaded, impact safety
face shield. Always use the full face shield when welding. Wear a NIOSH-approved dust
mask or respirator when working around metal, chemical dusts, fumes and mists.
9. Do not overreach. Keep proper footing and balance at all times. Do not reach over or
across running machines.
10. Maintain tools with care. Keep tools sharp and clean for better and safer performance.
Follow instructions for lubricating and changing accessories. Inspect tool cords periodically
and, if damaged, have them repaired by an authorized technician. The handles must be
kept clean, dry, and free from oil and grease at all times.
11. Disconnect power. Unplug tool when not in use.
12. Remove adjusting keys and wrenches. Check that keys and adjusting wrenches are
removed from the tool or machine work surface before plugging it in.
13. Avoid unintentional starting. Be sure the switch is in the Off position when not in use
and before plugging in. Do not carry any tool with your finger on the trigger, whether it
is plugged in or not.
14. Stay alert. Watch what you are doing, use common sense. Do not operate any tool when
you are tired.
15. Check for damaged parts. Before using any tool, any part that appears damaged
should be carefully checked to determine that it will operate properly and perform its
intended function. Check for alignment and binding of moving parts; any broken parts
or mounting fixtures; and any other condition that may affect proper operation. Any part
that is damaged should be properly repaired or replaced by a qualified technician. Do
not use the tool if any switch does not turn On and Off properly.
16. Guard against electric shock. Prevent body contact with grounded surfaces such as
pipes, radiators, ranges, and refrigerator enclosures.
17. Replacement parts and accessories. When servicing, use only identical replacement
parts. Use of any other parts will void the warranty. Only use accessories intended for
use with this tool. Approved accessories are available from Harbor Freight Tools.
18. Do not operate tool if under the influence of alcohol or drugs. Read warning labels
on prescriptions to determine if your judgment or reflexes are impaired while taking drugs.
If there is any doubt, do not operate the tool.
19. Maintenance. For your safety, service and maintenance should be performed regularly
by a qualified technician.

Page 4SKU 54878 For technical questions, please call 1-800-444-3353.
20. Use proper size and type extension cord. If an extension cord is required, it must be
of the proper size and type to supply the correct current to the tool without heating up.
Otherwise, the extension cord could melt and catch fire, or cause electrical damage to
the tool. This tool requires use of an extension cord of 20 amps minimum capability (up
to 30 feet), with wire size rated at 12 AWG. Longer extension cords require larger size
wire. If you are using the tool outdoors, use an extension cord rated for outdoor use
(signified by “WA” on the jacket).
Note: Performance of this tool may vary depending on variations in local line voltage. Exten-
sion cord usage may also affect tool performance.
Warning:The warnings, cautions, and instructions discussed in this instruction manual
cannot cover all possible conditions and situations that may occur. It must be under-
stood by the operator that common sense and caution are factors which cannot be built
into this product, but must be supplied by the operator.
Welding Safety Warnings and Precautions
Warning: This product, when used for welding and similar applications, produces
chemicals known to the State of California to cause cancer and birth defects (or other
reproductive harm). California Health & Safety Code 25249.5, et seq.
1. Avoid electrical shock. Do not permit electrically live parts, cables, or electrodes to
contact skin, clothing, or gloves. Protective clothing should be hole-free, dry, and ANSI-
approved.
This unit draws enough current to cause serious injury or death. Before turning the welder
on, check the electrode holder to be sure that there are no protruding screw heads, and
that all insulation is secure. Do not weld unless you are insulated from ground and the
work piece.
2. Avoid breathing fumes or gases. They can cause serious health problems. Use an
active ventilation system directly above the welding area. Keep your head out of the
fumes.

Page 5SKU 54878 For technical questions, please call 1-800-444-3353.
Assembly
1. Attach the Handle (30) to the Cover (31) using screw (29) inserted from the Handle top-
rear. Refer to the photo at the top of page 6, and the Assembly Drawing on page 10.
2. Attach the Cover Locking Spring (8) to the front of the Base Frame (14) using the supplied
self-tapping screw.
Unpacking
When unpacking, check to make sure the following parts are included.
Wire Spool and Spare
Welding Tip not shown
Torch (1)
MIG-100 Welder
Power Cord
Ground Cable
If any parts are missing or broken, please call Harbor Freight Tools at the number on the
cover of this manual as soon as possible.
3. Avoid eye and body damage. Welding rays and infrared radiation can injure eyes and
burn skin. Wear ANSI-approved eye and body protection. Do not allow viewing by visitors
without proper eye and body protection. Use a face shield with arc-shaded filter plate.
4. Know proper welding practices. Read and understand the manufacturer’s instructions,
as well as your employer’s safety practices for welding.
5. Connect only to a code approved power source. Connect only to a grounding power
source conforming to the National Electrical Code and Local Codes.
6. Avoid fire and explosion. Remove flammable and explosive material from at least 35
feet from the welding site to prevent welding sparks or molten metal from starting a fire.
Keep a type ABC fire extinguisher within easy reach. Thoroughly clean the object being
welded of any paint, grease, or other foreign material.
7. Avoid being burned. Always wear ANSI-approved welding gear: leather gloves, leather
apron, and shoes.

Page 6SKU 54878 For technical questions, please call 1-800-444-3353.
Note: What does the term “duty cycle mean?
Duty cycle is a welding equipment specification, which defines the number of minutes, within
a 10-minute period, during which a given welder can safely produce a particular welding cur-
rent. For example, this 90 amp welder with a 10% duty cycle must be rested for at least 9
minutes after 1 minute of continuous welding.
Failure to carefully observe duty cycle limitations can easily over stress a welder’s
power generation system contributing to premature welder failure. Many welders do
not have internal protection systems that prevent this sort of over stress -- leaving the
task to the owner or operator.
Operation
This Welder is used to weld sheet metal and light carbon steel.
Caution: Before welding, read and understand all safety precautions and warnings
listed on pages 2 through 5.
Cover Locking Spring (8)
Cover (31)
Handle (30)
Wire Reel (27)
Switch (7) Power On / Off
Switch (7) Current Min. / Max.
Overload Indicator Light
Wire Feed Speed Knob (9)
Torch (1) Cable
Ground Cable (33) Power Cord (32)

Page 7SKU 54878 For technical questions, please call 1-800-444-3353.
1. Securely clamp the Ground Cable Clamp (33) as close as possible to the metal object
to be welded, or to the metal work bench where the object is mounted and electrically
connected.
2. Set the switch on the control panel to MIN or MAX, as appropriate.
3. Verify that the Power Switch is in the OFF position, then plug the MIG-100 Welder
plug into a dedicated, 110 VAC, 20 amp line with delayed action type circuit breaker or
fuses.
If an extension cord is used, it must have the following wire size: up to 30 feet, use 12
AWG size wire; 30 to 50 feet, use 10 AWG wire; Over 50 feet, use 8 AWG wire.
4. While holding the Torch Cable Clamp with electrode wire clearly out of the way of any
grounded objects, turn the Power Switch to the ON position.
5. Momentarily press the Torch switch to test the wire feed speed.
Adjust the speed by turning the Wire Feed Speed Knob (9).
6. Orient yourself on the area to be welded, then place a face shield over your eyes.
Warning: Never look at the ignited arc without ANSI-approved,
arc-shaded, eye protection in a full face shield. Permanent
eye damage or blindness can occur. Skin burns can occur.
Never breathe welding fumes.
7. Press (and hold) the Torch button and stroke the area to
be welded with the electrode wire to ignite the arc.
Never tap the electrode wire into the welding surface to
ignite the arc. This damages its external coating on the
electrode which prevents oxygen in the air from coming
into contact with the molten metal, causing it to oxidize.
8. Once the arc is ignited, tilt the electrode wire forward at an angle of approximately 35°.
The wire feeds automatically at a speed dependent on the Min. or Max. current setting.
Note: If too much current is drawn from the Welder, the Thermal Overload protector will
activate, the amber indicator will light, and the Welder will turn off until it cools down. If this
happens, turn the Power Switch to the OFF position and wait about 3 ~ 5 minutes.
9. When the weld is complete, lift the electrode wire clearly away from any grounded
object, set the face shield down, turn toward the Welder, and turn the Power Switch to
the OFF position.
10. Unplug the Power Cord from the electrical outlet.

Page 8SKU 54878 For technical questions, please call 1-800-444-3353.
Maintenance
Caution: Before performing any maintenance on the Welder, unplug the Power Cord
from the electrical outlet.
1. Periodically remove the Right and Left side panels (12 and 13), and using compressed
air, blow out all dust from the interior.
2. Store in a clean and dry location.
Replacing the Wire Reel
When the wire on the Feed Reel is used up, you will need to replace it as follows.
1. Press on the Cover Locking Spring (8), then lift the Cover (31) using Handle (30) to
expose the Wire Feed Unit (23).
2. Unscrew the Wing Nut (25) and remove the Reel Locking Knob (26).
3. Remove the empty Wire Reel (27).
4. Place the new Wire Reel over the shaft and onto the Reel Spring (24).
The wire on the reel should unwind counterclockwise (see
photo above).
5. Replace the Reel Locking Knob and the Wing Nut.
Tighten well.
6. Lift the Wire Feed Adjusting Spring (36) to remove
tension.
7. Guide at least 12 inches of wire into the Torch Sheath.
If the end of the wire is crimped or bent, cut it off.
8. Replace tension to the Wire Feed Adjusting Spring (36).
9. Turn the Torch Handle Nozzle counterclockwise and pull to remove.
Wire Sheath
Wire Feed Adjusting Spring (36)
Tension Adjusting
Screw (37)

Page 9SKU 54878 For technical questions, please call 1-800-444-3353.
10. Turn the Contact Tip counterclockwise and remove.
11. Lay the Torch Sheath out in a straight line so that the wire moves through it easily.
Warning: The following steps require applying power to the welder. Do not touch any-
thing with the Torch Handle or an arc may be ignited.
12. Plug the Power Cord into its electrical outlet, press the Current Switch to Max., and
turn the welder ON.
13. Lift the Torch Handle and continue pressing the Trigger until the wire feeds through two
inches.
If the wire does not feed, view the Wire Feed Unit and see if the wire is being pushed.
If it is not, turn the welder OFF and add more tension to the Wire Feed Adjusting
Spring (36).
14. Turn the welder ON again and press the Trigger.
15. Once the wire is exposed, turn the welder OFF and unplug it.
16. Slide the Contact Tip over the wire and screw it into Torch Handle.
17. Replace the Nozzle and cut off any excess wire over two inches.
18. Secure the Cover.
PLEASE READ THE FOLLOWING CAREFULLY
THE MANUFACTURER AND/OR DISTRIBUTOR HAS PROVIDED THE PARTS DIAGRAM IN THIS MANUAL
AS A REFERENCE TOOL ONLY. NEITHER THE MANUFACTURER NOR DISTRIBUTOR MAKES ANY
REPRESENTATION OR WARRANTY OF ANY KIND TO THE BUYER THAT HE OR SHE IS QUALIFIED TO
MAKE ANY REPAIRS TO THE PRODUCT OR THAT HE OR SHE IS QUALIFIED TO REPLACE ANY PARTS
OF THE PRODUCT. IN FACT, THE MANUFACTURER AND/OR DISTRIBUTOR EXPRESSLY STATES THAT
ALL REPAIRS AND PARTS REPLACEMENTS SHOULD BE UNDERTAKEN BY CERTIFIED AND LICENSED
TECHNICIANS AND NOT BY THE BUYER. THE BUYER ASSUMES ALL RISK AND LIABILITY ARISING
OUT OF HIS OR HER REPAIRS TO THE ORIGINAL PRODUCT OR REPLACEMENT PARTS THERETO,
OR ARISING OUT OF HIS OR HER INSTALLATION OF REPLACEMENT PARTS THERETO.

Page 10SKU 54878 For technical questions, please call 1-800-444-3353.
Welder Parts List
Item # Description Qty
1 Torch 1
2 Contact Tip 1
3 Nozzle 1
4 Liner 1
5 Fixing Pole (A) for Gun Body 1
6 Fixing Pole (B) for Gun Body 1
7 Switch 2
8 Cover Locking Spring 1
9 Knob 1
10 Nut 1
11 Speed Control Circuit Board 1
12 Right Side Panel 1
13 Left Side Panel 1
14 Base Frame 1
15 Foot 4
16 Washer 4
17 Self-tapping Screw, ST4.2*13 4
18 Transformer Carriage 2
19 Thermostat 1
20 Transformer 1
Item # Description Qty
21 Middle Partition Board 1
22 Overload Indicator Lamp 1
23 Wire Feed Unit 1
24 Reel Spring 1
25 Wing Nut, M6 1
26 Reel Locking Knob 1
27 Wire Reel 1
28 Reel Holder 1
29 Self-tapping Screw, ST4.2*25 1
30 Handle 1
31 Cover 1
32 Power Cord 1
33 Ground Cable 1
34 Wire Feed Roller 1
35 Wire Feed Bearing 1
36 Wire Feed Adjusting Spring 1
37 Adjustment Screw 1
38 Face Shield 1
39 Wire Brush / Hammer 1

Page 11SKU 54878 For technical questions, please call 1-800-444-3353.
Welder Assembly Drawing
NOTE: Some parts are listed and shown for
illustration purposes only and are not avail-
able individually as replacement parts.

Page 12SKU 54878 For technical questions, please call 1-800-444-3353.
35
34
36 35
23
19
28 24
20
23
11
Welder Assembly Photographs

Page 13SKU 54878 For technical questions, please call 1-800-444-3353.
Wiring Schematic

Page 14SKU 54878 For technical questions, please call 1-800-444-3353.
WARRANTY
Harbor Freight Tools Co. makes every effort to assure that its products meet high quality and durability standards,
and warrants to the original purchaser that for a period of ninety days from date of purchase that the torch, liner,
wire feed mechanism (if applicable), welding clamps, electrode holders, cables and accessories packed with the
welder are free of defects in materials and workmanship. This Limited 90 Day/1Year Warranty shall not apply
to consumable parts such as tips, welding wire, and gas nozzles. Harbor Freight Tools also warrants to the
original purchaser, for a period of one year from date of purchase, that the transformer and rectifier are free from
defects in materials and workmanship.This warranty does not apply to damage due directly or indirectly to misuse,
abuse, negligence or accidents; repairs or alterations outside our facilities; or to lack of maintenance. We shall in
no event be liable for death, injuries to persons or property, or for incidental, contingent, special or consequential
damages arising from the use of our product. Some states do not allow the exclusion or limitation of incidental
or consequential damages, so the above limitation of exclusion may not apply to you. THIS WARRANTY IS
EXPRESSLY IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS.
To take advantage of this warranty, the product or part must be returned to us with transportation charges prepaid.
Proof of purchase date and an explanation of the complaint must accompany the merchandise. If our inspection
verifies the defect, we will either repair or replace the product at our election or we may elect to refund the purchase
price if we cannot readily and quickly provide you with a replacement. We will return repaired products at our
expense, but if we determine there is no defect, or that the defect resulted from causes not within the scope of
our warranty, then you must bear the cost of returning the product.
This warranty gives you specific legal rights and you may also have other rights which vary from state to state.
3491 Mission Oaks Blvd. • PO Box 6009 • Camarillo, CA 93011 • [phone]
Limited 90 day/1 year warranty