Hard to help without touching car.
Idea/guesstimate: Possibly small hose vacuum leak (heat could help seal or reduce leakage allowing it to function?)? Bad AC switch (defective/warped connectors affected by heat - cold no contact; hot full contact)?
Intermittent electrical problems are the worst!
Good Luck!
Idea/guesstimate: Possibly small hose vacuum leak (heat could help seal or reduce leakage allowing it to function?)? Bad AC switch (defective/warped connectors affected by heat - cold no contact; hot full contact)?
Intermittent electrical problems are the worst!
Good Luck!