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A TIG welder that powers up but will not start an arc usually has a problem in one of five areas: setup, tungsten, work-clamp connection, gas flow, or the machine’s start controls. Check them in that order. It avoids replacing parts when the real fault is a loose ground clamp or an electrode contaminated with steel.
Start with safety
Turn the welder off before inspecting internal wiring, removing covers, or changing damaged torch parts. TIG machines can retain hazardous voltage after they are unplugged. Do not bypass the torch trigger, interlock, fuse, or thermal protection. Wear a properly rated helmet, gloves, long sleeves, and eye protection when grinding tungsten. Make sure the area is ventilated; stainless steel, galvanized coatings, and unknown painted metal can produce dangerous fumes.
Confirm the machine is actually ready
Check the input power first. Verify that the machine is plugged into the correct voltage and that the breaker has not tripped. A 120-volt TIG machine may be limited to roughly 100 to 150 amps, while a 240-volt machine can support more output. If the front panel is dead, check the outlet, extension cord, plug, and breaker. Avoid long, light-gauge extension cords: voltage drop can prevent startup or cause nuisance faults. A short 12-gauge cord is a reasonable limit for many smaller machines; follow the welder’s manual when it specifies otherwise.
If the panel shows an error, fan warning, or over-temperature symbol, let the machine cool for 15 to 30 minutes with its vents clear. A thermal shutdown can prevent an arc even though the display remains lit. Also check the process selection. The machine must be in TIG mode, not stick or MIG mode, and high-frequency start or lift-arc mode must match your torch and setup.
Inspect the torch and start control
Press the torch trigger while watching the machine. You should normally hear gas flow, a relay click, or see a start indicator. If nothing changes, inspect the trigger plug and control cable for bent pins, cuts, or a partially inserted connector. A broken torch switch will stop both gas and arc initiation on a remote-start machine.
Some welders are configured for a foot pedal or hand control. If the machine is set to remote control but no pedal is connected, it may not deliver current. Set the control to panel mode or connect the correct remote. A two-pin torch switch and a multi-pin foot pedal are not interchangeable simply because both plug into the front panel.
For a lift-arc setup, the tungsten must touch the work briefly before you lift it. Do not drag it across the metal. If you are using high-frequency start, keep the tungsten approximately 1/16 to 1/8 inch from clean metal and press the trigger. Excessive gap, a dirty workpiece, or a cracked ceramic cup can make the spark fail to jump.
Check the work clamp and metal
Clamp directly to clean, bare metal. Rust, mill scale, paint, oil, and welding-table coatings can interrupt the circuit. Scrape a small area with a grinder or wire brush, then attach the clamp firmly. Inspect the cable where it enters the clamp; broken strands can leave the clamp looking secure while carrying little current.
Test with a short piece of clean mild steel rather than an anodized, plated, or heavily oxidized part. Put the clamp close to the weld area. A long path through a dirty welding table can produce a weak or nonexistent arc. If the arc works on clean steel but not on the job, the problem is preparation or workpiece conductivity, not necessarily the welder.
Prepare the tungsten correctly
A contaminated or loose tungsten is one of the most common causes of failed TIG starts. Remove the tungsten and check that it is straight, sharp enough for the process, and held tightly by the collet. The collet must match the tungsten diameter. A 3/32-inch tungsten in a 1/8-inch collet may not grip correctly.
Grind tungsten lengthwise, not around its circumference. For DC welding steel and stainless, a pointed tip with a small flat is a useful starting point. If the electrode touched the work or filler rod, grind past the contaminated section. Use a dedicated tungsten grinder or clean abrasive wheel; a wheel used on mild steel can embed contaminants. For AC aluminum, use the machine’s recommended electrode and tip shape rather than assuming a large ball is always correct.
| Symptom | Likely cause | First check |
|---|---|---|
| No gas and no arc | Trigger, remote setting, fuse, or control connection | Trigger plug, panel/remote mode, error code |
| Gas flows but no spark | HF setting, excessive gap, dirty work, or torch fault | Clean steel test and 1/16–1/8-inch tungsten gap |
| Arc starts only when touching metal | Lift-arc mode selected or HF not functioning | Process and start-mode settings |
| Arc starts, then stops | Loose ground, thermal protection, or remote-control fault | Clamp, duty-cycle indicator, pedal/trigger |
Verify shielding gas and consumables
Gas does not create the arc, but an empty cylinder or failed solenoid can reveal a torch-control problem. With the regulator connected, open the cylinder valve and check the flowmeter. A common starting range is 15 to 25 cubic feet per hour for a standard TIG cup. Too little flow allows contamination; excessive flow can create turbulence and pull air into the shield.
Listen for gas when you press the trigger. If there is no flow, confirm the cylinder valve is open, the regulator is connected, and the hose is not kinked. A damaged torch head, cracked gas hose, blocked gas lens, or stuck solenoid needs inspection. Replace cracked cups and badly eroded collets rather than trying to seal them with tape.
If you need replacements, a basic TIG torch consumables kit is inexpensive and useful for eliminating worn small parts. Buy a kit that matches your torch series and tungsten diameter; generic parts are not always interchangeable.
Use a controlled test
Set the machine to DC TIG, begin around 60 to 90 amps for thin mild steel, connect the work clamp to clean steel, and use a freshly ground tungsten. Select panel control, choose HF start if available, set gas flow near 20 cubic feet per hour, and press the trigger with a 1/16-inch gap. This removes variables one at a time.
For aluminum, switch to AC only after DC operation is confirmed. Aluminum usually needs AC balance and frequency settings within the machine’s recommended range. Do not diagnose an AC setup using a contaminated tungsten and dirty aluminum; both can make a functioning welder appear defective.
When to service or replace the welder
If the machine has power, a good clamp, clean steel, correct settings, and a known-good torch but produces no HF spark or current, internal components may be at fault. Possible failures include the HF board, relay, output diode, torch-control circuit, or a blown internal fuse. Stop testing if you smell burnt insulation, see arcing inside the case, or find heat-damaged connectors.
For occasional repair work, a budget AC/DC TIG welder with HF start can be a practical replacement if the repair quote approaches half the cost of a new machine. If you mainly weld steel and stainless, a DC-only unit is cheaper and simpler. Choose a repair shop when the machine is under warranty, has specialized controls, or is a professional unit worth protecting.