2005 volvo vnl bunk heater issue

My bunk heater does not turn on. There are times it will work. When I have the ignition in the on position the fan will come on but it won't go from hot to cold. When the truck is idling it will change from hot and cold. When the truck is off it won't turn on and right now it just won't turn on for anything. I have to remove the fuse and then replace it to work or I have to do a reset by removing the panel and removing the wires then replacing them for it to work sometimes. When I first got the truck the panel would beep constantly then I did the reset and it stopped. Anyone know the issue?

 

Here is the panel. It is a Behr heater core I believe

 

Ok makes sense how much does it cost to get one of those installed?