I brought my car into mehcnaic A for a flickering dash lights problem. After replacing the 3 month old alternator and computer (~$550) the problem still wasn't fixed and new problems had popped up.
After replacing a grounding cable myself the original issue was solved, but the new ones persisted. Upon taking my car to a different mechanic in regards to the new problems, they informed me that the mechanic A had put the wrong type of computer in my car and didn't even program it to work with my car. Now i've already paid a little over $400 to repair the issues caused by having the wrong computer installed and will have to pay even more to get the computer replaced as the current one has only been reprogrammed and runs without issue, but won't pass inspection without replacement.
Mechanic A also replaced the alternator without my permission and simply told me the amount due and that i'd have to come pay it to get my car back. I now know this was illegal and I could have taken my car back without paying, hindsight, eh? I would have told them no if they had asked, since the alternator was brand new only three months earlier. I don't think I should have to pay for repairs on damage that was caused by mechanic A, which can be proven by mechanic B. Especially when they failed to at least fix the issue I brought the car to them for in the first place.
Make a written demand to the first mechanic for all your money back and the cost of additional repairs necessary as a result of his negligent work. If he does not pay you, then tell him you will report him the State of California Bureau of Automotive Rpair. If he still resists, report him to the Bureau. Also if he is an authorized repair service by AAA or someone else file a complaint also the better business bureau.
If you get nowhere hire an attorney or go to small claims court and seek redress.
Please note this message does not create an attorney-client relationship or is this message intended as legal advise.