Volvo Repair: 86 Volvo 240 wagon Heater, volvo 240 wagon, air thermostat

Question
The heater on my '86 240 wagon blows cold, OK, luke warm air. I think our mechanic might have done something last time we brought it in for another problem, because it seemed to blow hotter air for a few weeks. But then it got really cold out (Michigan) and now it is totally useless, and I am freezing but sick of pouring money into my beautiful wagon. I would like to figure out how to fix it myself. What things should I look at?  

Answer
Hi Tara,
          Listed are reasons..why the heater is blowing cold air..
             Thermostat is broken...replace it.
             Very low fluid level in radiator.
             Kink or bend in heater hose.
             Heater control switch stuck.
             Lots of foreign material in heater core.
             A/C is on...shut of switch on dashboard.
              Heater control cable has problems.

           Some of these items need experienced repairman to assess and repair...sorry.
                 Good luck,
                             Bilbo