1988 Mercury Grand Marquis blows hot air when accelerating uphill and downshifting. Does this with or w/o a/c running. What is causing this?
The a/c will temorarily blow hot while downshifting during acceleration. Also, warm air comes out of vents w/o the a/c or ran running during acceleration and downshift. Vacuum issue? Otherwise, the a/c and compressor work normally and blows cold.