Changing fan/blower speed

[funkyg]

2020 Polo GTI+ with manual heating and AC settings.
I just noticed something over the last couple of days while having the air con running and having the blower set to number 2. While driving normally the blower speed remains constant but if I lift off the accelerator to allow the car to slow down the blower speed seems to pick up and get slightly louder/faster. Has anyone else ever noticed this? I don't think there is a problem it's just a quirk I've noticed.

[johnparker]

Hi
Mine does this too. Its strange but it is normal. There have been posts about this previously on this forum.
I think it still does this without the AC being on.

[PoloGTInoob]

Yep mine does this too

[Harrihealey02]

Your car's alternator cleverly adjusts its power output based on driving conditions. During normal cruising or idling, the alternator's draw on the engine is normal.
However, when you accelerate, the car intentionally reduces the alternator's load. This frees up engine power for smoother acceleration with less drag. This is why you notice a slight decrease in fan speed as the alternator prioritises supplying power to the engine.
Once you ease off the accelerator, the alternator ramps back up to its normal output, recharging the battery and powering your car's accessories.

[funkyg]

Your car's alternator cleverly adjusts its power output based on driving conditions. During normal cruising or idling, the alternator's draw on the engine is normal.
However, when you accelerate, the car intentionally reduces the alternator's load. This frees up engine power for smoother acceleration with less drag. This is why you notice a slight decrease in fan speed as the alternator prioritises supplying power to the engine.
Once you ease off the accelerator, the alternator ramps back up to its normal output, recharging the battery and powering your car's accessories.

Huh! That makes a lot of sense, thank you for the explanation. I wonder how many bhp the engine saves by throttling the alternator. Marginal gains!

[Johntheo1]

Your car's alternator cleverly adjusts its power output based on driving conditions. During normal cruising or idling, the alternator's draw on the engine is normal.
However, when you accelerate, the car intentionally reduces the alternator's load. This frees up engine power for smoother acceleration with less drag. This is why you notice a slight decrease in fan speed as the alternator prioritises supplying power to the engine.
Once you ease off the accelerator, the alternator ramps back up to its normal output, recharging the battery and powering your car's accessories.

Huh! That makes a lot of sense, thank you for the explanation. I wonder how many bhp the engine saves by throttling the alternator. Marginal gains!

Once the accelerator pedal is pressed the alternator only charges at a constant 13.2/13.3V and ramps up to a constant 14.4/14.7V while coasting, it also charges at a constant 13.3V while idling, while driving normally I now notice on my Jan 2019 polo that it will occasionally ramp up to 14.4V for 20 secs or so and then return to 13.3V and in very cold weather if the car has been parked up for a week or so while on holidays it will charge continuously at 14.4V
for 30 minutes or longer before returning to 13.3V.