Automotive Welding: How to Weld on a Car 2022

This site contains affiliate links to products. We may receive a commission for purchases made through these links.

Everybody loves an appealing and functioning car that boosts the driving experience. If there is a problem, fix or upgrade your vehicle’s components or body to make it silky smooth.

A good way of addressing auto body fixes and attaching metal components is through welding. However, welding on a car involves passing electricity through the car body. Welding the metal parts require special techniques. 

Can there be damage? If done wrongly, you can get damage. Since welding a car requires passing electricity through the metal parts which are attached to the vehicle’s electronics, there is a high possibility of damaging your car if you don’t do it properly.

How do you avoid causing damage to the car? Carefully observe the safety precautions to avoid frying up your electronics.  

The safety precautions enable you to weld safely without damage. Safe automotive welding requires limiting the amount of electric voltage going through the car’s electronics as you weld to make the work safer with no damage.

Why Does Automotive Welding Cause Damage?

When you weld on a metal, you need to first create an electric current from your welding torch to the metal. The electrical current passes through the metal and if there are electronics connected to the metal, they also get the current. 

Electric current can damage your inner electronics like dashboard computers. The vehicle’s computer controls manage your engine besides firing the pistons. The car computer is also known as ECU that can suffer irreparable damage preventing you from driving the vehicle. The ECU is essential to the car’s functioning. Make sure you protect it when welding your car. 

How Do You Protect the ECU during Welding on a Car?

Your car ECU needs voltage or battery power to run, and it’s designed to use a small amount of power the car battery delivers. Welding uses a high voltage which can make the electrical voltage reach the ECU, causing damage. What happens if you weld without disconnecting the battery? The voltage will damage your car’s computer and other electronics. Damage to the ECU affects the functioning of the car. 

To avoid shorting your ECU or preventing damage, follow the steps below when welding your car. 

Remove the Negative Terminal of your Car Battery

A car battery has a positive and a negative terminal with the positive terminals being red and the negative terminal being black. Loosen the negative terminal from the battery using a screwdriver. Removing the negative terminal reduces overvoltage when the electric current is flowing through the battery. 

Ground your Working Area

Use the welder’s earth grounder to ground your working area. Carefully attach the grounder to the metal you are welding to dissipate away voltage from your car to the ground. Dissipating voltage keeps away excess energy from the vehicle’s ECU. 

Disconnect Vital Electronics

Even after disconnecting the car battery you still have some residual energy left in the parallel circuits which can still control critical electronics like airbags and ECU. The additional electrical voltage coming from the welding and residual energy cannot short circuit the electronics but can trigger your airbags.

Disconnect Airbag Connectors

Follow the steps below to disconnect your car’s airbag connectors. 

Locate the airbag module. You can find the module on the floor beneath the radio, under your carpet, underneath the driver’s seat, or under your car’s center console. 

Find the SRS computer module. You can find it under your center console or the driver’s seat or center dashboard. 

Disconnect the car battery’s positive cable. This is the cable with a (+) symbol. Disconnect it and wait for 3 minutes for the residual energy in the circuit to dissipate. 

Unplug your airbag control module. This is a harness or a plastic box with some wiring plugs coming from it. Unplug it to stop the firing of airbags. 

Disconnect the ECU

This is your primary aim to protect it from damage when welding the car. Preserving the vital computer protects your engine and car functioning. Follow the steps below to safely detach it and keep it safe. 

Double-check if the negative terminal is fully disconnected. 

Remove the panel hosting the ECU. You can find it under the glove box on the passenger section, open it to get to the ECU. 

Unplug your ECU. ECU is silvery, loosen the bolts securing it to the vehicle using a socket wrench, then safely remove them.

Best Automotive Welding Methods

Preferably you can use MIG welding or TIG welding. Stick welding has many risks, although some people use it in automotive restoration. At the moment MIG welding is the best and by far the most popular choice for welders. For a car body, you can do a lap, butt, and off sheet lap joint where MIG welding is most effective. 

How to Weld a Car Body

When welding on a car, you want the job to be perfect, which requires precision and the best welding technique. Ugly splatter means you spend more time chipping the pieces away, setting your work back unnecessarily.

Before you start, ensure you wear proper safety gear like a welding helmet and gloves. Exposure to bright lights and toxic fumes can ruin your eyes.

Make sure the room has proper ventilation to avoid the buildup of toxic fumes.

Follow the tips below to weld the car effectively.

Take things Slow as you Weld the Car Body

If it’s your first time welding a car body, it’s advisable to take it slow for a better result. This minimizes any chances of making mistakes like warping or putting a hole in the metal sheet. Patience is necessary as welding a car is a delicate process. 

Begin with a Lower Power Setting Available

The aim is to help you work with something more comfortable because of the nature of the metal sheet. Metal sheets used in cars are quite thin, and you can easily poke a hole in them if you begin with a higher power setting. 

Clean the Metal Sheet Section before Starting

Cleaning the metal prevents the oxide layer from forming. All metals need cleaning before welding or your labor will be in vain. 

Measure before Starting

Accurately measure the sheet of metal to avoid creating holes during welding. Without measuring, you may not know you have poked holes when you finish. Measure the joints and other areas properly before starting your welding to prevent having joints that don’t fit. 


Can you MIG Weld on a Car?

MIG welding helps you correct the auto body problem without damaging critical things. You can MIG weld a car frame. Always observe safety measures to avoid unwanted situations like damaging your car’s electronics. You can safely MIG weld your car by following the steps below. 

Ensure you have a small wire diameter to avoid plunging holes in the metal sheet. A small wire diameter gives you flexibility in case you mess as it inflicts less damage on the metal. 

Never use a thinner base metal when welding a car body if you want the best results. 

Opt for a shielding gas with a higher argon gas proportion instead of a higher carbon dioxide percentage. This prevents too much splatter. 

Avoid using flux-cored wire in automotive welding of sheet metals because it makes the base metal more prone to heat. 

Can you Stick Weld on a Car?

Stick weld is the shielded metal arc welding or SMAW. The welding technique was once a common option for most welders. Stick welding uses filler metals just like TIG but lacks precision. The welding technique uses high heat, which is unsuitable for welding thin metals and leaves behind ugly splatter.

Stick welding is great for construction projects but not recommended for welding on a car. 

Can you Use a Welder to Jump Start a Car?

Never attempt to jump-start your car using a welder. If you do, be ready with a fire extinguisher as you will need it to salvage whatever is left of the car. Use proper equipment to jump-start the vehicle.

A welder has 32VAC and 100amp. Why will it not work? Because your ECU module is sensitive to high voltage and will be damaged. Remember, it’s expensive to replace ECU, so never try it. 

Can you Weld Exhaust while on a Car?

 Yes, it’s possible. You don’t have to worry about the floor pans as they won’t get hot enough. Tack everything up, then run a full weld. However, don’t run a bead while working over your head to avoid getting burned by the molten metal pieces. 

Why do Welders Drink Milk?

Welders drink milk to prevent metal fume fever. Welding releases fumes that can make you sick. Milk is a treatment for metal fume fever mostly caused by exposure to magnesium oxide, aluminum oxide and zinc oxide produced when heating metals including galvanized steel. 


Automotive welding can damage your vehicle’s electronic components, which is why unplug the ECU and disconnect the airbags before you start. Follow the simple guidelines highlighted above to weld on a car successfully. MIG welding can handle auto bodywork and leave a good impression. 

Welding is a rewarding skill, although it has its challenges. Use the best techniques to do the job right with no damage to the auto body. Modern MIG welding is easy to master with little guidance, although you need more practice to breeze through the challenges in no time. 

Reference from car care lab

Special offer for our visitors

Get your Welding Free Guide

We will never send you spam. By signing up for this you agree with our privacy policy and to receive regular updates via email in regards to industry news and promotions