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Join Date: Jul 2010
Location: New Jersey
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am i this dumb...welding on car...CDI not working

so i have been doing a ton of body work on the car and came across two small rust spots about size of dime...i wanted to cut them out and replace with new metal...

i pulled the car out of the garage and grind them off, it was a nice sunny day so i decided to leave it in the driveway...

hook up my MIG welder, and go to town...

the spots are on the quarter panel back by the CDI...

i got done the repairs, i always keep a rag in a bucket of water and ice to put on car after each weld...

turn key to pull car back in and NOTHING from CDI....

would something like this fry the CDI? or did my CDI just die on me...

car turns over, battery is super strong, both fuel pumps are running.

Old 05-30-2012, 04:16 PM
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Yep, it can kill a CDI, alternator, or other delicate electronics.

Rule of thumb is to always get the work clamp as close to the weld as possible, unhook the ground cable on the battery and unplug the ignition, alternator and other electronics.

Lucky for us, we don't have too many electronics
__________________
1986 911 Turbo
3.3L, K27HFS, Tial 46mm, TurboKraft Intercooler, 964 Cams, Monty Muffler, MS3Pro Evo, M&W Ignition, Zietronix WBO2 Data Logger, Wevo shifter, coupler and motor mounts.
Old 05-30-2012, 05:15 PM
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Quote:
Originally Posted by WinRice View Post
Yep, it can kill a CDI, alternator, or other delicate electronics.

Rule of thumb is to always get the work clamp as close to the weld as possible, unhook the ground cable on the battery and unplug the ignition, alternator and other electronics.

Lucky for us, we don't have too many electronics
ok, so before i go welding anymore, what is the best way with all this in the car? i dont want to do anymore damage
Old 05-30-2012, 06:08 PM
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Don't feel bad, I've been there on other projects.

First, disconnect the battery ground.

Second, put the work clamp close to the area being welded on good clean metal. If the clamp moves around, it can arc and cause spikes.

Third, unplug the engine harness to body harness plug to isolate the alternator.

Fourth, unplug the CDI.

Some guys go to the effort of unplugging gauges. The most sensitive would be the tach and speedo.

Some guys get lucky and never have an issue, sometimes it'll fry a couple of things. On an old Chevy I fried a Mallory Unilite module and the alternator regulator.

__________________
1986 911 Turbo
3.3L, K27HFS, Tial 46mm, TurboKraft Intercooler, 964 Cams, Monty Muffler, MS3Pro Evo, M&W Ignition, Zietronix WBO2 Data Logger, Wevo shifter, coupler and motor mounts.
Old 05-30-2012, 07:48 PM
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