On Saturday, I had a new stereo installed into my 99 Caravan.  Yesterday, when I started my van, the airbag and ABS lights were illuminated on the dashboard panel for about two minutes.  During that time, I couldn't turn on the A/C and the turn signal indicators didn't work.  Suddenly the A/C kicked in and the turn signals worked again.  This has happenedly only once.  What could be the cause?  Thanks!  

Not sure but I had speakers installed in my truck then my windows and wipers would not work. I took it back and they found that they DID NOT plug the wires in correctly.  I'd take it back or take it to the dealership.  Airbags and ABS are not a fun thing to play around with...you're life's riding on these things to work if you're involved in an accident.