Which cable should I disconnect first? I’ve always heard the negative should be first, but I would think the positive should be first than the negative. Thank You. George
Disonnect the negative terminal first.
Electrically speaking, it makes absolutely no difference which terminal is disconnected first. The given advice is a safety consideration.
If you are working on the positive terminal first and your wrench touches any other metal part of the car (which is presumably grounded) you have created a short circuit. Not a good idea!
If the same accident happens when you are first tackling the negative terminal there is no problem.
The same rationale applies to connecting a battery. Connect the positive terminal first, then do the negative terminal.