i hear a constant cricket sound when i turn on the AC or heat...except for today...the day i took it in to be looked at.

have you ever experienced this? its so annoying.

any ideas for a fix?

 

Without even knowing what year or model of vehicle you have, I would say it is probably the bearing in the blower motor.

Options: replace the blower motor, or remove it and see if you can lubricate the bearing in the motor.

 

You mean you can't even guess what is causing the noise???????????????????
When does it happen, if it is when you are trying to turn on the fan, it is the blower motor, either bad or with leaves in it.