Toyota Repair: 1986 Toyota PU 2.4L 22R, toyota dealer, heater core

Question
My heater had started going in and out with heat and cold air.  There is enough water in the systema and I had replaced the thermostat.  I went to the Haynes auto manual to try and replace the core and to no avail, did not understand the sequence of directions and photos.  It seems the manual did not cover my truck.  Any advice where to look or what could be the problem?

Answer
Hello DJ, welcome to my expert page,
It sounds like the heater core is the problem, it's located right in the center under the dash and somewhat difficult to remove,I don't know if there is a repair manual at my work going back to 86, try to get one from the toyota dealer or get back to me with an email address and I may be able to mail some instructions, like I said, it depends on whether there is a manual available to me.