Heater blows some times
my heater come on when it wonts too, I put in a new thermostat but it still blows warm air when it is blowing.
Check to make sure coolant is circulating through the heater core, thse older model cars have a vacuum operated valve on the heater hoses that needs to open to allow coolant to flow through the heater core, find it and see if it's working
this 92 Cad Deville has no valve on the hose, it have a T tube which is new and new thermostat
It may be the programmer (under the dash) or one of the temperature sensors. You'll need a factory shop manual to properly diagnose this system. Sounds like it's not fully going to heat mode. HTH. -Jim
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