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No Hot Air - 765T[ALL/1988] posted by John Acampora on
Wednesday, 18 February 1998, at 10:54 p.m.
My 87 765T has auto climate control and is not delivering hot air. The climate controls are acting strangely. When I set the temp dial to 70+ degrees to heat, I can hear the fan running inside the dash put no air is coming out of the vents. On the low fan speed the fan seem silent. In the defogger mode I get alittle air out of the fog vents but it is not hot, maybe just barely warm. When I dial in a lower temp of say 60 and below the airconditioner comes on and the vents seem to work normally with cold air to the vents. I just put in a new Nissen 3 row radiator, seems to be working fine. The heater hose going into the heater core are getting hot, the lower hose with the heater valve in it is hotter than than the return hose. I assume hot coolant is getting to the heater core.
My Haynes manual talks about a coolant thermal switch in the heater hose, but my car does not have one there. Something looks like it screwed into the engine block underneath the intake manifold. A note in the manual says that if this switch is accidently disconnected the heater blower will not work at cabin temperatures below 64 deg F regardless of coolant temperature.
Appreciate and help that can be offered.
TIA
John
87 765T 123K
Re: No Hot Air - 765T[ALL/1988] posted by abe crombie on
Wednesday, 18 February 1998, at 11:51 p.m.
There is a one wire switch on the block under intake above starter that you seem to have found. It provides a ground to ACC unit. Try grounding it to see if that gives you relief. The blend door may be seized and not allowing the controller to move is another possibility. You can get to it by removing glove box. The controller has a lever with a link rod snapped into it, take note of how much of the end of the rod is exposed so you can put it back to the same adjustment after you check for free movement of the door. That system has a vacuum operated heater valve, it is open unless there is vacuum applied to it. If it is not getting vacuum you should go to defrost but it would be able to be hot and fan would vary speeds as you reun temp wheel up and down scale. That system will always be able to go to max hot if you run temp wheel to highest temp if it is working correctly. A shorted temp sensor would make it go full cold until you run temp wheel to full hot position.