Nissan Repair: 1996 Nissan Sentra alarm, amp fuse, nissan sentra

Question
My daughter had a new battery installed in her car and the installer had the cables reversed. Blew the main 75 amp fuse. After I installed a new fuse, everything worked except her alarm system and the radio. Any suggestions to fix these? Could the battery cables reversed have blown out the alarm system and radio beyond repair. Is it possible that a relay was affected?
Any help would be great.
Thank You
Karl

Answer
Karl,

I would check the fuse links at the battery cable first.  The alarm, if aftermarket, has a fuse in-line, that can be replaced.  Also, on the motherboard, inside the alarm box, there is a fuse that protects the circuit.  With the cost of aftermarket alarms being about $100 bucks it is probably just as cheap to replace it with a new one.  If we are talking about the factory alarm I would be checking the fuses and relays for open circuits.  The radio is the same with aftermarket ones having their own fuse along with the one in the fuse box.  Now, if both are blown and replaced and the radio still does not work you are looking at a replacement.  The thing here that gets me is that you did not say the alternator was damaged.  Usually, when the battery is hooked up backwards it blows the rectifier out of the alternator.  And, this is the best part for you that the computer that drives the engine did not get damaged.  I have seen ones where the electronic control module had to be replaced due to the battery being hooked up backwards.  I would hope the installer is liable for the repairs?