jvandyke Posted October 22, 2018 Share Posted October 22, 2018 trying to help my kid get some heat in the cabin, '72 240. Chevy 350zz4. Has some flavor of dealer installed A/C. So, turning on the fan we get air through the center and two side vents but nothing to the floor or defroster, I assume the A/C system's fan replaces the OEM one? So what directs air where? Quote Link to comment Share on other sites More sharing options...
jhm Posted October 22, 2018 Share Posted October 22, 2018 If the HVAC system has been replaced and/or modified by a previous owner, there's really no way to answer your question. The stock system is very simple and straightforward. A valve controls the amount of hot water coming through the heat exchanger and mechanical cables operate the flaps to direct the air into the cabin. If you're not getting airflow from the lower vents in the footwells or the defroster vents, either the flap's not directing the air where you want it or the ducts are not transporting the air where you want it. When you switch ventilation modes (e.g. from vent to heat to defroster), can you hear the flap system moving? It usually makes a very obvious sound when it's being manipulated. The AC modifications may have rigged the system to only blow air through the central vents; but the only way to know for sure is to dig into it. They could have disabled components of the system by removing control cables, removing certain ducts, blocking off certain parts of the ducting system, etc. That would be my guess from your description of the issue. BTW, from your picture....that is the stock blower, so it does not appear that the AC modifications replaced the OEM blower with an aftermarket blower. Quote Link to comment Share on other sites More sharing options...
jvandyke Posted October 22, 2018 Author Share Posted October 22, 2018 (edited) 2 hours ago, jhm said: BTW, from your picture....that is the stock blower, so it does not appear that the AC modifications replaced the OEM blower with an aftermarket blower. Really? I have lots to learn apparently. I assumed that was the A/C blower. Okay so there's a flap inoperative. I think it maybe right behind the center vent (well, deeper in near #6 here: That would totally make sense. Which lever is supposed to close that dude off? Edited October 22, 2018 by jvandyke Quote Link to comment Share on other sites More sharing options...
jhm Posted October 22, 2018 Share Posted October 22, 2018 The same blower is used for heat, fresh air, defrost and AC (even on dealer-installed AC systems). You may possibly have two flaps inoperative, if you are getting neither heat in the footwells nor defrost on the windshield. I would also check the ducts feeding the defroster. They can often pop off their inlets/outlets, or just disintegrate altogether....they're made of some kind of cloth material. Quote Link to comment Share on other sites More sharing options...
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