I have a cold air leak on the right front side of my CAB?

Hello,

Can you tell if the air leak is from the top or the bottom of the cab?

If it is from the top, it can be due to a leaky window seal. Window seal can dry rot or simply some off the channel and create a leak.

An improperly closed door can also allow air to enter the cab.

If the leak is from the bottom or under the dash it could be due to any of the seal/plug that goes into the firewall. They can come of and create the leak. It can also leak around HVAX housing. There is typically a foam seal that goes around the housing which keeps air from coming through any gap.

So really be course of action would be to first feel for where the leak is coming from and take appropriate action.

Please let me know what you find or if you have any questions.
Thank you.