Landseer

Have read quite a bit about this in archives; no concensus.

Tommorow, or Thursday at latest, will have car at shop / some exhaust welding / some brackets to body. Don't want fried brain.

I plan to advise these guys to disconnect negative battery cable.

Should I also unplug brain at passenger footwell?

Enough?

69gaugeman

For the couple of minutes it takes do it. Unplug brain.

Sailmed

Isn't welding just a rapid fire exchange of electricity creating extreme heat and fusion?
What could it possibly hurt if your brain had a few stray pulses

69gaugeman

It's the huge voltage and amperage

the flyin' scotsman

Disconnect the battery and both brains for surity.............if you need convincing check out the price of replacement.

GUMBALL

YES, DISCONNECT BOTH COMPUTERS and BATTERY..!!


In the process of welding, when the arc is first struck, there is a LARGE voltage spike, and that spike can kill computers, as well as relays, motors, servos, etc, etc

dr bob

Make Darn Sure that the welder's ground clamp is on the metal he/she is welding, and put it close to where they are welding. Don't let them attach the clamp to frame ground, since the return path will be through the engine and the engine ground cable.

Landseer

Thanks. I'll pull most of the relays as well.

JHowell37

You don't have to pull the relays. Trust me. Most folks here talk about welding on a 928, I'm one of very few who have actually done it. Leave the relays in place and disconnect the brain. Because I had such a hard time diagnosing a defective LH as the source of my problems last year, I went so far as to remove it from the car before welding. If that makes you sleep better then go for it. But don't pull all relays. Also have them disconnect the battery.

jon928se

Dis the -ve to the battery and take the brains with you when you leave the car. they can push it around the shop.

If your car has the expensive headlight relay I'ld be tempted to remove that as well.

$ paranoia is the reasoning behind my comments - no real sound engineering or science

GUMBALL

I have worked in a shop where a customer car was towed in for "no-start".....after long testing process (with several calls to the owner) found that the car had come from a body shop where they had TIG welded a crack in a front fender, without disconnecting the battery or the computers.
Both brains were damaged.

Rick Carter

I dodged a bullet when I had the plates for the six point harness welded to the floor and also when the eye bolts were welded to the bar bewtween the rear shock mounts. Just another in the long list of the stupid things I've done.

Landseer

Car is done and back home. Thanks for the advice on the disconnect points.

Pure excellence from the shop. Older gentlemen was a craftsman with the exhaust. When I came to pick up the car he told me he unplugged the brain and disconnected the battery, plus grounded his MIG on his work just like I'd asked.

I had left the relays, but worried all afternoon about it.

(Sounds very good, exactly like I wanted, would change nothing. Dual in/out cat, dual magnaflows, final dual in/out magnaflow. He ran the mid mufflers just a little lower than some of you guys have, but it created great space for the rest of the pipes.)

Paul Dortkamp

Oops, read this too late. Took the S4 in to have a small bit of welding done near a lower front suspension pickup point. After the repair the S4 starts OK but has very low power, can barely keep up with the traffic, moves off the mark at glacial pace and has harsh gearchanges. I drove it home but now suspect fried brains. The exhaust smells like mineral turpentine. I think this is the begining of a learning experience. Just have to find some brains locally to swap and check.

aggravation

Sounds exactly like my symptoms when I left a coil wire loose.....