When the AC "cycles", the electric clutch at the compressor pulley engages, this couples the pulley and the A/C compressor, the compressor starts to turn.
The compressor is an additional load on the engine. On some cars, people notice a hesitation while driving, I am not sure why though. Just better observers, maybe.
At idle, the ECU is supposed to open the IAC valve a little to raise the rpm a second or two before the compressor turns on, so you actually see a small movement up in rpm if you happen to be watching he needle at the time.
Sometime when you are stopped for a while with the AC on, look at the rpm, and wait for the AC to cycle. There should be a small "bump", just before it happens. That will pretty much tell you if all is working as it should. (easier to observe at idle with little other load on the engine)
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
SaabCentral Forums
3M posts
119.1K members
Since 2001
SaabCentral forum the most comprehensive Saab resource on the internet. Join our discussions on the Saab 9-3, Saab 9-5, Saab 900, Saab 9000 and all other Saab models, choose your forum.