how to haggle a car repair price
Car repairs cost money, and this is how to haggle the price down while still getting the work done right.
In the United States, there are four options when you want your car repaired. Two of them you can haggle with and usually see good results, while for the others... not-so much.
Option 1 is a new car dealership, option 2 is a used car dealership, option 3 is a regional auto repair shop, option 4 is a local auto repair shop.
With option 3 and 4, you ordinarily can't haggle the price here. These shops are stretched thin, barely make any money, will always cut corners, use crappy replacement parts, and invent problems with your car where none exists. You don't want to go to these places.
The only way to get the price down with options 3 or 4 is to be an AAA member, and then see if the garage is listed in AAA. If they are, then you can present your AAA membership and should get a discount... assuming the shop doesn't add in extra cost to defeat the discount, which they might.
A specific situation where option 4 might work out (even if not an AAA-Approved garage) is if you own a Chevy or Ford gas-powered (meaning not diesel) non-luxury pickup truck that's over 10 years old. Local repair shops are usually very familiar with these, and proper new replacement parts are easier and cheaper to source when compared to foreign. In other words, if you own a Ford F150 or Chevrolet Silverado from 2012 or earlier, the local guys usually know how to fix those for a decent price. Both are common, both have parts readily available, both are usually easy to service.
With option 2, the answer here is, "it depends".
Carmax, in my experience, actually does have decent auto repair and maintenance service for cars bought from them. I very appreciate that most Carmax repair shops are brutally honest where they'll a) just outright admit they cost more than other shops do, and b) not upsell you because they have no reason to. Sometimes they'll even tell you what shop you should use to get a better repair price. They do have a little wiggle room where haggling a repair price is concerned, but not all that much. And no coupons.
For other used-car-only dealerships, the general rule of thumb is they don't do good repair work unless they specialize in a specific brand. For example, there are some smaller used dealerships that are very specific, such as Toyota-only, Volkswagen-only, Subaru-only, and so on. They don't necessarily cost less (and usually don't), but the familiarity with all the particular quirks of a specific brand usually means the work will be done right.
Then there is option 1, the new car dealership...