First thing to remember is to be very very thourough when inspecting the customers vehichle. You need to be sure you and your company are not liable for this problem. It does seem unlikely that after 3 years the remote start caused the issue, however I have been in simaliar situations and sometimes the best way to prove your install didnt cause the problem is to find the real problem. I had a guy that had his RS for a year or so and all of a sudden he kept blowing fuses for his parking lights on the left side. Of course the dealer said it was the RS so when he came in I first went through all of our connections and wires to ensure there was no shorts, bare wires, broken insulation and most importantly not a failed unit. After all that everything looked good so I went looking for the real problem. Everyone in the shop gave me a hard time because they felt it wasnt something we caused so why keep looking. It took me an extra 20 min to pull his rear left tail light to find that he had an aftermarket trailer light T harness that was shorted out because he didnt get a cover for the plug that sits under the trailer hitch. That was the real problem, and Im sure I could have spent way more than 20 min arguing with him that it wasnt our install that caused the problem. Once I unplugged the trailer hitch harness no more blown fuses and I pulled him into the shop to show him suddenly he rememberd that he had just had a trailer hitch installed and was actually told by the shop that he bought it from to purchase a cover for the harness plug because water will get in and short it, but he opted not to.
Any way if it s a problem with his factory radio display I know there is or at least was some factory defect with the display on 03 and up Accord factory radios, google it. Dont accept any "quotes" for repairs. I had one of my guys set off an airbag light, (removed seat , replaced seat, and forgot to plug airbag switch for seat back in.) My installer saw the light before the car left the shop and the switch was reconnected but once the air bag code was stored only the dealer could clear it. The dealer cleared the code for free but this guy came in with a quote for 148 dollars and wanted cash in hand. I just explained that i needed a paid reciept for the repairs to reimburse him. We did however give him a great deal on some other items he was looking to purchase because of the time he had to spend getting the code cleared. Free or not we caused it.
Last thing is dont take photo copies of reciepts for repairs. We sent someone to the dealer to get a new key made because one of my installers dropped the customers key and it bounced into a sewer drain. Sounds stupid but actually happened. So this guy goes to the dealer gets a new key made and comes back with a bill for 200 dollars or so but it was a photo copy. I had already talked to the people at the dealership and they quoted me at 60-85 dollars. The guy got an oil change while at the dealership, then took the reciept and used white out or something to cover it on his reciept then copied it and came into the shop with the copy so the only thing showing on His copy was the key. I dont know if it was photo shop or what but the guy did a nice job, lucky for me I had a freind that worked there. Wow, this didnt seem as long of a post in my head.