Cadillac Repair Questions? Ask a Mechanic for Answers ASAP
Hi There, I'm Clay a certified master automobile technician with 30 years of automotive repair and diagnostic experience.
From your description most likely there is no or low vacuum supply to the control head. When there is no vacuum supply to the control head the system kind of defaults to vent with low flow to the floor. Under the hood there should be a vacuum reservoir, it should have a black vacuum hose and a violet hose. Verify there is vacuum to and from the reservoir with the engine running. Also with the engine running listen inside of the vehicle for vacuum leaking from under the dash. You can also check for HVAC trouble codes by pressing fan up and fan down at the same time for 5 seconds. Then push the Auto button. Codes are numbered 00 thru 10. "00" indicates no codes. Let me know what all you find.
I hope this information is helpful. If you have any questions or run into any problems let me know.
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