I think (and another 737 pilot here with me) that as soon as you push the LNAV button to intercept the track the HDG Select button will extuingish and LNAV will illuminate. If I have a chance to check this in the near future I will.
So the behaviour is different than when intercepting a LOC under HDG and engaging the APP button. In the LNAV case, the HDG light goes off immediately, while in the APP case it goes off only when the LOC is intercepted. I hate these inconsistencies :-)
Stamatis
[This message has been edited by Stamatis (edited 18 September 2000).]