What would cause the 4 wheel drive to not engage on a 95 Chevy Blazer the module containing the 4x4 button was replaced however the light does not go on in 4 wheel hi 4 wheel?

4 wheel drive module located in the passenger side kick panel. Most likely condensation got in the plug. About 450.00 to replace it at a dealer! Checked on 7/27/07.