Just thought I'd share a humorous story since I'm sure many of you have dealt with this kind of customer at one point or another. This is a long one. :)
A few months ago, the store I work for installed a remote start/security system on a customer's truck. We'll call this customer "Bob." From the get-go, we knew Bob was a real turd. He was annoying and questioned our experience at every opportunity (citing that he was a "mechanic for 15 years", yet he drives rigs... methinks his stint as a mechanic failed for reasons to be mentioned). The starter installed and worked fine and he was finally on his way.
A couple weeks later, Bob returned, explaining that we screwed his truck up. He said our installation of the starter was causing fuses to blow left and right. Bob did not have fog lights on his truck when he first brought it in, but now we noticed he had them. One of the other installers asked if he had the fog lights put on since the installation, and Bob proudly said yes, he installed them himself, and they shouldn't have anything to do with his problems. So we took a look at his vehicle and found the problem almost immediately: he had tampered with the wiring for the remote starter, and actually spliced power for his foglights off the ignition wire. He denied having touched anything, yet at the same time he had an awful hard time explaining how the fog lights wound up connected to the starter wiring. We fixed his problem, and sent him on his way.
Only a couple weeks later, we heard from Bob again. He returned to have us uninstall the remote starter since he was going to be purchasing a new vehicle. The R/S was removed and we "anxiously" awaited his return for reinstallation. The next week, Bob showed up for his reinstallation with an older GM (I actually forget the model now). It was in horrible condition and the Service Engine Soon light was on. We explained that we can't proceed with any installations until the SES light is checked and cleared by the dealer. He was furious and gave us the "I was a mechanic for 15 years" rant. Explaining the reasons why we don't work on cars with the SES lit, and sticking to our guns, he finally gave up and left. He came back for his rescheduled appointment a few days later and I was lucky enough to get to check his car in. He told me he had put the car on his own code reader and that it was just "a transmission code thrown from the previous owner who spun the wheels out." He went right into the old "mechanic for 15 years" rant on me and kept telling me that he really doesn't think any of us are qualified "to make that sort of decision". I politely informed him that if he was concerned about our experience and skill, he is more than capable of installing the R/S himself. He stopped nagging and quietly went inside to sign the paperwork.
While we were finishing his paperwork, he made another comment to my supervisor about how us "installer people really shouldn't be making the decision to turn away vehicles with the SES on". So my supervisor began to explain that if a car comes in with the SES, ABS or airbag lights on, we can't touch it. He blurts out "Airbag light? You won't work on a car if the airbag light is on? Do you even know how an airbag works?" Begin yet another "mechanic for 15 years" rant. Calmly my super explained that its a safety standard to prevent any electrical system problems from causing an airbag to, in the worst case scenario, deploy (or not deploy when it should).
This guy was the ultimate P.I.T.A. customer and hopefully we never have to see him again. He came back several times after breaking the antenna off remote for the starter, claiming it was defective and somehow it was our fault... even though he admitted that he sat on it.
One of the many morals of this story: know-it-all customers may be mechanics but they sure aren't electricians. :)