Cadillac Repair: 1992 ECON, auto theft siu investigation, chad tredway

Question
I have a 1992 Cadillac and when I push auto on the dash for heat ECON comes on and when I push the red for heat to like 90 it stops blowing out of the front vents and it reroutes to the defrost vents but it does not blow out hot air when I turn down the heat to like 60 it reroutes to the front vents but blowing cold air. The service light comes on to service airconditioner

Answer
Hello,

First the a/c is a separate system from heat and should not be your concern at the moment.
You have a vacuum issue under the dash not opening the correct plenum doors. There are doors that control the direction of the air.

As for the heat, could be numerous issues. Low radiator, bad radiator cap, plugged cooling system. Bad heater control valve at engine.

With engine warm, touch all the hoses to make sure they are hot. Check the hoses leading to the fire wall where the heater is located. If only one warm, either circulation problem in heater or heater control valve not engaged.

The heater control valve is also operated by vacuum, so you need to find your vacuum leak. It could be at the control as well.

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