Welding question

notfarnow · 07-20-2007, 10:26 AM

The rear sway bar mount broke off my dad's car, and he brought it over to have it fixed.

After dropping the sway bar, I had a guy down the road MIG weld the mount.

He insisted that we disconnect the battery before he welds. He said that MIG welding could damage electrical components in the car.

Makes sense, and I was glad to play it safe, but I had never heard of that before. Was he being overly cautious, or can MIG welding (or other types) actually damage electrical components?

Joeaksa · 07-20-2007, 10:53 AM

He is correct. The diodes in the alternator can be damaged by welders. Good call on his part.

BGCarrera32 · 07-20-2007, 11:12 AM

In the basic sense MIG, TIG, and stick are a localized eletrical short circuit to heat the metal to melting temp for welding. Isolating a direct ground path back to the welder by disconnecting the battery is a wise move.

notfarnow · 07-20-2007, 11:15 AM

Good to know, thanks!

trekkor · 07-20-2007, 11:33 AM

On the flip side, I've done close to 20 hours of welding on my car with the battery connected without problem one.

Probally a better idea to disconnect. Don't know if I will though.

KT

Joeaksa · 07-20-2007, 03:10 PM

Quote:

Originally posted by trekkor
On the flip side, I've done close to 20 hours of welding on my car with the battery connected without problem one.

Probally a better idea to disconnect. Don't know if I will though.

KT

How many diodes are in the alternator? 6-8 I believe?

What if one or two of them are knocked out by welding every so often? The "charging" light is connected to ONE diode only I believe, so until that specific diode is not working you have no idea how many you have in the system working. When that one diode fails then the charging light comes on and tells you you have a problem.

Its cheap insurance to disconnect the battery and in our cars pull the "14 pin connector" in the back to isolate the electrical systems when welding.

on2wheels52 · on2wheels52's Garage

I can remember my dad and uncle disconnecting to battery before doing some farmer welding on the combine.
Would a generator sustain damage if left connected?
Jim

sketchers356 · 07-20-2007, 04:44 PM

Cheap insurance, but I have a hard time that this has ever happened under normal circumstances.

bobp53916 · bobp53916's Garage

We had made the mistake of not disconnecting the battery before welding on 2 vehicles in our body shop, once burned out a distributor and 2nd time an ECU...Learned the hard way...

Joeaksa · 07-20-2007, 08:57 PM

Quote:

Originally posted by on2wheels52
I can remember my dad and uncle disconnecting to battery before doing some farmer welding on the combine.
Would a generator sustain damage if left connected?
Jim

Jim,

Generators are not as sensative as alternators. Pretty simple to tell the truth inside. Still I would disconnect the system before welding.

trekkor · 07-20-2007, 09:02 PM

I'll disconnect from now on.

Thanks

KT

sketchers356 · 07-21-2007, 06:55 AM

Quote:

Originally posted by bobp53916
We had made the mistake of not disconnecting the battery before welding on 2 vehicles in our body shop, once burned out a distributor and 2nd time an ECU...Learned the hard way...

Stand corrected.

john70t · 07-21-2007, 07:11 AM

A lot of powertrain/body computers operate at 9 volts and don't last long being exposed to 14V+ directly from the alternator. A welding machine puts out much more than that.

Joeaksa · 07-21-2007, 07:32 AM

Quote:

Originally posted by john70t
A lot of powertrain/body computers operate at 9 volts and don't last long being exposed to 14V+ directly from the alternator. A welding machine puts out much more than that.

As I have been told, its not the amount of volts as much as the spike of the current each time the spark is struck between the torch and frame of the car. Also if your grounds are not good then it backfeeds through all sorts of things, doing wonders to electrical components.