air condition setting

ok i've encountered this a few times wth a couple vehicles, especially subarus and a few mazdas and nissans. the thing is i go through my normal routine of installing the alarm on the car, i don't remove any jacks i don't normally remove. but when i'm finished and i'm running the vehicle through to make sure everything is functional that was fuctional when the customer brought it in. the air condition controls go wack, to get cold air from the car you have to adjust the setting on the controls to the lowest, and as soon as you adjust the temperature setting from 18degrees to 18.5 degrees extremely hot air comes through the vents. i spoke to a guy who works for the local bmw firm and he tells me that's how it normally works, but i don't believe so. anyone encounter this before if so how'd u fix it? i believe it has to do with the car's computer, but the thing is how does it happen,

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COMMIT YOUR WAY TO JEHOVAH AND HE WILL ACT IN YOUR BEHALF. PSALMS 37:5

Luckily half my lot never check their AC and no jokes about the English climate, my AC is on 4-6 months of the year, also wouldn't think you'd get this problem with the Japanese cars, their AC isn't processor controlled like BMW. Rule of thumb with Euro cars, never ever unplug anything with the ignition on. Thinks why would you even go "near" the AC circuits, do you disconnect the battery? If so DON'T the only reason to disconnect would be if yoyu were going to get near airbag electronics such as removing the steering wheel.

i don't unplug anything with the ignition on, neither do i go near a/c circuits, which is why i can't figure why i happens, it happens rarely, but i just wanted to know if anyone had an idea or a solution to it, for the customers sakes, thanks howie. any more info would still be appreciated

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COMMIT YOUR WAY TO JEHOVAH AND HE WILL ACT IN YOUR BEHALF. PSALMS 37:5

I've got a feeli ng it will revert to normal settings after about 10-20 miles.

i guess  that's what happens, cuz da customers never come back, lol

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COMMIT YOUR WAY TO JEHOVAH AND HE WILL ACT IN YOUR BEHALF. PSALMS 37:5