Cooling System/Heater Core Question

[tturse@ps-b.com (Thomas Turse)]

Hey all, quick question about my 85 4ksq.  I've been noticing that the car
has been running a little more hot lately- usually about 1/2 on the gauge
and now mostly the upper 1/3 to the upper 1/4.  Also, not sure if this is
related, but when I put the defrost on or any heat function, the air stays
hot.  I checked the temp slide switch and it's closing the inside gate all
the way.  Could this be a cooling system blockage-  a line to heater core
blocked.  I just hope its not the core itself because I don't think it would
be worth replacing- probably a really expensive job.  Any suggestions would
be very much appreciated, as always.  Please send any responses to me
directly, as I have been unable to stay on the list.  Thanks.

Thomas
85 4ksq
Boulder, CO