UK-POLOS.NET - THE VW Polo Forum

I've noticed on my SE with manual air con, that the blower fan speed keeps varying in speed. It becomes slower and less noisy when accelerating and conversely noiser when taking my foot off the accelerator. This occurs on both the first and second speed settings. Never had this on any other car.

Has anyone else noticed this and is it normal?

Is this just not due to VW Group's and maybe others approach to a cheap version of regenerative braking - ie when accelerating the alternator will be either not charging or charging at a low level (smart alternator control), and on the over run the car's kinetic energy is used to "cram" charge into the battery - so the PD of the battery is higher. On a clever system, I would have expected that there would be a stabilised power output for all 12V services, seems for some low priority power users that this is not the case - which is okay in the real world, just annoying.

Wife’s first Nissan Juke with manual air con used to do this but her second Juke with climate control never did it, it always annoyed me as it was quite noticeable.

I noticed my cars air con dips too when you depress the peddle.

The mystery deepens!

Its because if the load on the engine, when under acceleration or load the engine is using more electricity for the spark so therefore theres less for the fan.