To my way of thinking, the NAV is always on or more correctly, always in the MOST circuit.

I think you can however loop the MOST connector going into the NAV unit and then yes, the radio will still work. Below is a jpg of a typical loop that would do the job.

The head unit generates the red light and the clock timing so I do not think the NAV is critical to the operation of the audio system but I may be wrong on that. The converse however is not true. You cannot loop out the audio head component and anticipate that the NAV will work.

If the NAV unit will not allow MOST signal to pass thru, then the audio system will be silent, hence jumping the MOST going into the NAV unit should allow the audio to function.

 

Radio can definitely be made to work without nav since not all lr3 came with nav

 

Yes, you are correct.

The MOST system HK installations that do not have the NAV installed use a different MOST cable that just runs between the Head Unit and the Amplifier. The bypass loop is only needed if the MOST cable is installed for the NAV unit as well but the NAV has been removed or is not operational.

There is also the low line radio that is a single head unit to which the speakers are wired and hence contains an internal amp much like is on most vehicles. In this setup, there is no MOST system at all.