after installing new battery in 98 dodge minivan, lights on buttons controlling ac, rear wipers,rear window heater flash for about 16 minutes, dealer can’t figure out, and now turn signals no longer working
Make sure the connections on the battery are clean and tight.
How much time did you authorize for diagnostics?
Did he mess up a relay switch? If he took these relays apart to check them, did he put them back in the right places? Double check the ground wire on the alternator to make sure it’s on tight and that the rubber cover isn’t trapped under the nut/wire.
… Both ends of each cable.
On some of these cars, there’s a procedure for resetting the climate control system—you can probably find it by searching online. It usually entails holding down several buttons at once until something happens. Did the turn signals immediately stop working after the battery swap, or later on? If later on, it’s likely an unfortunate coincidence. Have you tried the simple procedure of disconnecting the negative cable, waiting about ? hour, and connecting it back up? It may just need to be reset again.