2002 Buick LeSabre air cond-heater problem

I posted this problem several months ago and problem has been solved. The problem was--when ambient temperature called for heat the heater would come on and run until the preset heat was achieved and shut down. Later when more heat was needed the blower would run full blast but no air came out any vent. Turned off the system, then about a half hour later turned on the system and it would produce heat again. The solution was--the evaporator was freezing up and blocking air flow caused by a defective (stuck open) regulating valve in the compressor. Same thing would happen if it was too warm inside car and called for cooling (sun shining thru windows) while cold outside.

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