2000 blazer problem

I purchased a 2000 blazer about 8 months ago. Since then the dealer has had to replace both seat handles(reclining) both sun visors, both door strips at driver and pass windows the front wheel hub , the driver window motor and last but not least i just had to have a new transmission and oil cooler lines . When the trans was replaced we now have a problem with our security light flashing and making a sound like as if a signal was on but the key isn't in the ignition. I don't understand what is making this noise and why it happened after they replaced the transmission. Can someone help me???