Low heat from HVAC?

Digitalchaos

Registered User
In recent times with changing weather, I have noticed the need to keep my HVAC controls set to full heat & fan to keep a desireable interior temperature. This is more pronounced if windows are opened an inch or two. It could be my imagination & (low cold-tolerance :D ), but it seems both the fan & temperature are inadequate.

Fan - Both side vents expell significantly less air than the middle vents. I am aware that there is always some air loss over a longer path, but there seems to be a big difference. Furthermore, I have read the '93+ vent ducts were supposed to be redesigned to enhance air flow from the sides. All vent controls are working & they are all fully open. The blower & its switch seem to function normally.

Temp - while the air being expelled from the vents is adequately warm when set to 90, its temp quickly decreases at any lower temperature. Also, there is very little difference at any setting lower than 90 down to about 70. It also does not seem to get as warm as other cars that I ride in, which get almost burning hot when settings are at maximum.

Now the first thing which comes to my mind is the thermostat. I have recently found that mine is leaking from the housing. However, the car always seems to reach proper temperature, & stay there without getting too hot. When its cold (50), it does stay around the N a lot longer.. which is less than normal. Does the thermostat on the SC independently regulate flow of coolant to the heater core?

Next thing I can think of is the heater core itself. While I do not know its condition, the overall condition of the cooling system seems excellent. Coolant was very clean when I bought the car, and has been changed twice in recent times for flushing & hose replacing. The lower hose is w/o a spring & has no problems with collapsing. The cooling capacity also seems more than adequate, from 90s to now 40s the car stays within range. This implies to me that the heater core is unlikely to be clogged.

A bit lengthy for a seemingly simple problem.. what do you think?
 
I assume you know the cooling system is full and that you don't have an air pocket correct? I also assume this is Electronic Climate control equipped car?

Have you had your dash apart lately to get to the instrument cluster?
 
Well.....I doubt at this point the heater core is clogged unless someone used Bars Leak in the system at one time. Unlike the "old" days where flow was restricted to the core to control temps in a T Bird they blend air to control the heat. Outside (or interior air depending on setting) and the air flowing over the heater core. If no heat is wanted then no air is allowed by the blend door to flow across the core.

My question about the dash is related to if there is really flow across the thermistor behind the cluster bezel just to the left of the radio position. There is a hose connection at that point where the sensor is mounted and the hose runs all the way through the dash to the blower where it hooks in. When the blower runs it draws air across the sensor. The one in my 92 was crimped and temperature control sucked both for the AC and heat function. The hose is a coiled wire reinforced plastic material tube.
 
Ok, thanks for the information. I now recall that the previous owner had replaced the oil pressure sending unit, so perhaps they had the dash apart for this. If so, maybe they accidently crimped it when reassembling.

Maybe I can access this hose & sensor by removing the radio.

Thanks again for your help!
 
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