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Repairing an aluminum radiator is a demanding TIG job. The material is thin, contaminated easily by coolant, and often cracked again by vibration or pressure if the repair is poorly prepared. The best welder is not necessarily the highest-amperage machine; it is one with stable low-amp control, AC TIG capability, adjustable AC balance and enough duty cycle for the work.
For most radiator repairs, a 200-amp AC/DC TIG welder is the practical sweet spot. A smaller 120-amp machine can work on thin tubes and tanks, while a 250-amp unit makes sense for heavy truck, industrial or fabricated aluminum radiators. DC-only TIG welders are not suitable for aluminum because they cannot break through the oxide layer effectively.
What to Look for in a TIG Welder
AC TIG is essential. Aluminum forms a tough oxide layer that melts at a much higher temperature than the base metal. AC provides cleaning action during part of the cycle, allowing the arc to penetrate the aluminum beneath it.
High-frequency start is preferable to lift start. HF starts the arc without touching the tungsten to the radiator, reducing tungsten contamination and accidental damage to thin fins or tubes. A foot pedal or remote amperage control is also valuable because aluminum quickly moves from cold to overheated.
Look for adjustable AC balance, usually expressed as electrode-negative versus electrode-positive time. More cleaning action helps with dirty aluminum but increases electrode heating and reduces penetration. A machine with a useful adjustment range, rather than a single fixed AC setting, gives you more control over different radiator alloys and levels of oxidation.
Pulse control is helpful but not mandatory. Low-frequency pulse can reduce heat input on thin tanks and tubes, though it cannot compensate for poor cleaning or an oversized weld. For occasional repairs, a welder with reliable basic AC TIG controls is usually a better purchase than a complex machine with menus you will rarely use.
For a broader selection, compare 200-amp AC/DC TIG welders with at least HF start, a foot pedal and adjustable AC balance.
Recommended Amperage and Features
| Radiator work | Useful machine size | Important features | Trade-off |
|---|---|---|---|
| Thin automotive tubes and small tanks | 120–160 amps AC | Stable low-amp output, HF start, foot pedal | Lower cost, but limited headroom and duty cycle |
| General automotive and motorcycle radiators | 180–210 amps AC | AC balance, pulse, gas pre/post-flow, remote control | Best all-around range; usually larger and heavier |
| Heavy truck or thick fabricated tanks | 220–250 amps AC | Good duty cycle, water-cooling option, high input capacity | More expensive and often needs a 240-volt circuit |
A cheaper AC/DC welder is fine if you repair a radiator a few times per year and the machine has the essential controls. Do not pay extra solely for a high maximum amperage. Radiator aluminum is commonly thin enough that low-current stability matters more than a 300-amp rating. Check the minimum TIG output, arc stability and pedal response before comparing maximum amperage.
Best TIG Welder Types for Radiator Repair
Compact inverter AC/DC TIG welders are the best choice for most home shops and mobile repair work. They are light, efficient and commonly provide HF start, AC balance and pulse in a reasonably small package. Many run on 120 or 240 volts, but their full output may require 240 volts. Verify the input plug and circuit requirements before buying.
Traditional transformer TIG welders can produce a smooth AC arc and are durable, but they are heavy and often lack modern pulse controls. They make sense in a permanent fabrication shop where weight is irrelevant. They are usually a poor choice for a garage repair setup.
Multiprocess welders can be worthwhile if you also need MIG and stick welding. However, confirm that the TIG function is true AC high-frequency TIG, not DC lift TIG. Some machines advertise TIG capability but cannot weld aluminum properly. A separate AC/DC TIG welder with a foot pedal is often the safer purchase if aluminum repair is the main job.
Torch Setup and Consumables
A typical radiator repair uses a 1/16-inch or 3/32-inch 2% lanthanated tungsten, a #7 or #8 ceramic cup, and pure argon. Start around 15–20 cubic feet per hour of argon, then adjust for drafts and cup size. Excessive gas flow can create turbulence and actually draw air into the shielding area.
Use a gas lens if the torch accepts one. It produces a smoother, wider shielding stream and makes it easier to keep the tungsten and molten puddle protected. A compact air-cooled torch is adequate for small repairs; a water-cooled torch is more comfortable during repeated or high-amperage work.
For filler, match the radiator alloy when possible. 4043 aluminum filler is easy to use and flows well, while 5356 generally provides higher strength but can be less forgiving. Keep filler rod clean and dry. Store it away from grinding dust, oil and coolant.
Preparation Before Striking an Arc
Drain the radiator completely, flush it, and allow it to dry. Coolant trapped inside a crack can boil into the weld and cause pinholes. Remove paint, oxide, solder and sealant several inches around the repair. Degrease first, then brush the aluminum with a dedicated stainless-steel brush used only on aluminum.
Do not weld over a wet or oily surface. Aluminum oxide and contamination commonly cause black soot, wormholes, unstable arc behavior and leaks that appear only after the radiator heats up. If the crack is in a thin tube, stop-drill the ends with a small bit to reduce propagation, then fit the repair with minimal gap. Excessive grinding weakens the tube and creates a larger area to heat.
Begin with a low amperage and increase only as needed. Thin radiator material may require roughly 40–90 amps, but the correct setting depends on thickness, joint fit-up and heat sinking. Use the pedal to taper power as the puddle grows. Keep the arc short, add small amounts of filler and avoid lingering at the edges of the crack.
Testing and Common Failure Modes
After welding, clean the repair and inspect it under bright light. Let the radiator cool fully before pressure testing. Test below its normal operating pressure first, using a hand pressure tester if available, then increase gradually. Never pressure-test with compressed air while your face is near the tank; trapped energy can make a failed radiator dangerous.
The most common failures are pinholes from coolant contamination, burn-through from excessive heat, cracking beside the weld from inadequate preparation, and leaks caused by trying to bridge a wide gap with filler. If the surrounding aluminum is badly corroded or paper-thin, replacement is usually more reliable than adding weld after weld. TIG can repair sound aluminum; it cannot restore metal that has already lost its strength.
For occasional repairs, spend the budget on AC/DC capability, a usable pedal, clean gas delivery and careful preparation rather than cosmetic features. A dependable midrange inverter and the right setup will repair more radiators than an oversized welder operated with contaminated material.