Crashone...these systems allow about 20% fresh outside air (read hot air)...so to my way of thinking, the slower speed draws in less hot air, you get lower temps...high speed pulls in more hot air and you get higher temps at the nozzles...that and the faster moving air just has less time to cool off as it get blasted through the evaporator

I bet at night, the difference is much less as the outside air is somewhat cooler. I re-routed some vacuum lines, now have no outside air allowed, and much improved cooling as a result. If I want fresh air, I open a window!

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Mark
1983 300TD Wagon
Even a broken watch is right twice a day