Idle problems

[scotty]

I have a 92 318I when I turn the AC on the idle starts to jump from 500 rpm to 1400rpm what would cause that?

 

[mjbst111]

does it stay at 1400? the engine has to run faster to run the A/C. Well it doesn't have to but in order to get good cold air, it runs faster.

You'll have to provide a little more details.

 

[scotty]

it rev's up and down form 500 to 1400

 

[wz2wj1]

I have a 93 325I, with a 5 speed and mine does the same thing.

 

[Looky]

that's truly normal,

to produce max. cooling your AC-compressor needs more rpm but after some minutes full cooling the rpm had to sink automatically.

greets
Looky