autostart antenna

Long story short....had an Autostart remote starter professionally installed 5 years ago. I use the maximum start range of about 1200'. After a couple of years the range decreased significantly, so under warranty they replaced the antenna. It worked like new again. Now 2 years later, same thing. They didn't want to give me another antenna, so I just purchased one and they said it was plug-n-play, but should probably replace the harness (comes with it) also. Tonight I was short on time, but the temp was -5F, so I just unplugged the old antenna and plugged new one in just to see if it works. NUTHIN'...didn't respond at all. So I plugged the old one back in and it works. What am I doing wrong? Model # of new antenna is the same. I will check my original installation instructions when I get home, but just thought I'd put this out there for any suggestions. Thanks. Ed

you probably have to program the remotes to the new antenna...

They didn't say anything about programming, and I asked them several times.  The only thing they suggested was that I make sure to relpace the harness too.  I have the original installation instructions and it says nothing about programming the remotes to the antenna.  I'll give it another try, and if I can't get it to work, I'll just let them do it and pay the upcharge.  Thanks.  Ed