# re. jumpy idle on neutral when AC on



## jleholeho (Jul 8, 2016)

Hi everyone,

is here anybody who could point me in the right direction with this issue?
I've been having a hard time fixing up a jumpy idle on my Scirocco 1.4 TSI 118kW MY2009, immediately after AC is engaged...rpm jump between 600-900, sometime it calms down (especially after a longer ride), but still, this hassle is really pissing me off.
All the possible causes have been checked: the throttle bodies were cleaned/aligned, battery was replaced a month ago for a brand new one, AC compressor belt was replaced as well...to no avail. AC has been refilled, is cold enough but the damn rpm, when in neutral, simply don't want to get stabilized...right after I hit the AC button...

In addition to the abovementioned, can a faulty alternator cause jumpy idle on neutral when AC compressor is engaged? I have noticed that my new battery never shows voltage higher than 13.6-13.9V and though I´ve never recorded any fault code on VCDS related to alternator itself, my mechanic is somewhat skeptical with these outputs and says the whole idle hesitation could be due to faulty alternator...most mysterious thing is that once I disengage AC, the idle on neutral has always been super smooth.

Thanks for helping me out.


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## Poetic50 (Feb 17, 2017)

It’s probably after the AC clutch engages or disengages the engine raises the rpm to keep up with the load.


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