For the last couple of weeks my A/C has been acting crazy with a mind of it's own. I get in the car start driving A/C blows on low speed and after 10-15 minutes it jumps to max speed. So that a sign of my Final Stage Resistor starting to go bad.
Charging does not help.
Turn car electronics on, don't start th engine, keep the door open and if you get low batty sign in 5 min then it's bad battery.
When battery gets weak, car starts shutting down non essential functions and changing Ac speed is non essential.
When I had the same problem I had batty checked by dealer plus 2 independent mechanics, and all said battery was good. I Gen had a resistor behind the instrument panel replaced.
Finally I did procedure outlined above, low battery popes up. I replaced the battery and AC HAS been working well.
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