January 4, 201313 yr My heater has always worked great but fort he last month or so it gets hot after running a bit but then blows cold air unless driving at freeway speeds. Last night my wife drove home from work after it had been snowing for a couple hours and no hot air to defrost the windshield and she was driving about 50 mph the whole way.Without tearing into anything yet what do you guys n gals think could be the problem or what should I try replacing first to keep the heat coming out of the vents at all times. By the way the engine temp is just as normal as always which the gauge reads less or at halfway which makes me think it shouldnt be a thermostat. Any info helps. Thanks Tony. Edited January 4, 201313 yr by subinewby spelling
January 4, 201313 yr Author Year and model information would be helpful. Oh yes Im sorry it an 83 gl coupe.
January 5, 201313 yr No difference in engine temp? Sometimes the heat starts getting goofy if you're running low on coolant, but you should notice your engine temperature rising and falling a bit. More likely would be blockage or gunked up heater core or lines. I forget the setup on these older subes, but there should be two hoses that run from engine to the dash and back again. I tested by unplugging both and running a garden hose through one. If water goes in one hose and out the other, it's not a blockage problem. If you can't get water through, you've got a block somewhere. Had this same problem on my old 83 Wagon. Never got around to fixing it as it was more of a mountain car anyway.
January 5, 201313 yr Author No difference in engine temp? Sometimes the heat starts getting goofy if you're running low on coolant, but you should notice your engine temperature rising and falling a bit. More likely would be blockage or gunked up heater core or lines. I forget the setup on these older subes, but there should be two hoses that run from engine to the dash and back again. I tested by unplugging both and running a garden hose through one. If water goes in one hose and out the other, it's not a blockage problem. If you can't get water through, you've got a block somewhere. Had this same problem on my old 83 Wagon. Never got around to fixing it as it was more of a mountain car anyway. Thanks man ill try it out.
January 5, 201313 yr it may also be a vacuum leak in the hvac system. but more likely the coolant issue
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