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welding to a P38


jules
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I'm having issues with a rear bumpers fixing heads having rotted off and I was going to weld a new bolt onto them.

last time I disconnected the battery on a P38 I fried the high low stepper motor ecu. is there any recommendations

I don't want to frie any more ECU's

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Jules, what were you welding when you fried the ECU?

It's a bit of a myth that if you disconnect your battery before welding then all will be. Ok, not a bad idea, but this still won't prevent your electronics from damage. Its all about the grounds on a vehicle. Welding doesn't use high voltage, but it does use high amperage. If you're welding on the chassis, your welding ground lead needs to be on the chassis. If you're welding on the body then ground to that body panel. There is no way you can ground to the chassis and then weld on the body without causing damage.

It is possible that there is one of those little ground wires that go from the ECU, or 'box to the chassis or body that became a welding lead. This could include the actual grounds inside the computer, so disconnecting your battery will not help. You would need to be sure that you have isolated the computers themselves by un-plugging them.

In Steve's case above the axle is mostly isolated from the body/chassis by bushes and he would have the welding earth close to the weld. Hence avoiding damage.

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form a safety point of veiw you should always disconnect the ecu i have had a transfere box ecu fry just from reconnecting the battery but as the motor was fubar unbeknown to me at the time i was left in the dog poo! seen quite a few ecu fried over the years by not disconecting and on a p38a even more need to disconect

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I did some welding on a p38, luckily it caught alight, the fire brigade were late getting there, luckliy it finally sorted all my problems! :D

:hysterical::hysterical: :hysterical: :hysterical:

We had a lovely works p38 hse - It had so many electrical problems that it was cheaper to scrap the thing than get the electrics fixed - Mind you, it's brand new main stealer replaced £5000 engine (yep thats correct £5000) did fit nicely in to my ninety and now runs beautifully thanks to megasquirt :D .

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I did some welding on a p38, luckily it caught alight, the fire brigade were late getting there, luckliy it finally sorted all my problems! biggrin.gif

laugh.gif

My dad always used to say half a right off is no use to man nore beast.....

My boss is into BMW's and from what I can tell a P38 is cheap and relyable motor in comparison....

we managed to get the fixings out without welding new head on...so I don't need to weld to it yet....

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Hi , this is a very useful thread, I have dreaded having to get someone to weld my silencer or something similar as the usual response in Cyprus is to say " we disconnect the battery, don't worry we always do it this way!"

Does disconnecting the ECU also isolate the other computers such as the transmission, can any other sensitive parts be fried?

So If I disconnect the ECU and ensure that the earth cable of the welder is connected onto the workpiece, the risks will be minimised. Except from fire of course!rolleyes.gif

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