Blower speed when recirculate is on is off

ASHRAF2016

MEMBER
2010 HYUNDAI ACCENT
1.6L
4 CYL
2WD
MANUAL
27,000 MILES

Hello,

I noticed recently that blower produce more air flow when recirculate is on while A/C is working, than when fresh air is on (recirculate is off).

A/C works fine when recirculate is on, once I turn it off, air flow becomes less while fan speed is the same. Temperature obviously raises because of the fresh hot air coming in but one does not expect air flow to reduce.

This problem does not seem to happen when starting the parked in the sun car, turning on the A/C on fresh air. The air flow is normal this time. The problem only happens after A/C and recirculate work for sometime.

I changed A/C filter recently with an OEM one, it is clean. I even removed filter and turned A/C and recirculate on then turned off recirculate keeping A/C on, same happened, air flow became less.

Talked to a local A/C guy, told me this is normal.

car battery will need to be replaced soon, if this matters. Also, some vibration might be there when blower is on full speed.

Thanks.

3 Replies

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

It is normal. Your vehicle's Air Conditioning system is designed to work while the Heating Ventilation and Air Conditioning (HVAC) is set to re-circulation mode. This is because your vehicle's A/C system works by removing the hot cabin air and replacing it with cooler air conditioned air. Your vehicle's A/C is literally taking the hot cabin air and transferring it to the outside of your vehicle. Here is a link for you to go to below:

https://www.2carpros.com/articles/how-a-car-air-conditioner-works

If you should have any other vehicle related questions, please feel free to ask, we are here for you.

Thanks,
Alex
2CarPros

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Friday, July 12th, 2019 AT 11:40 AM

ASHRAF2016

MEMBER
14 POSTS

Thanks Alex, It's normal then, the link you mentioned above sure clarifies how AC works, from it I might have an idea why this feeling of reduced air flow happens.

Today however, I tried again with no AC on at all. Simply turning blower on at full speed the noticing difference when recirculate is on and off, It still happens: air flow becomes less when fresh air comes in.

This made me think, could it be simply the effect of those intake grills at windscreen bottom outside the car. Actually they are kind of filters with big holes to trap leaves, insects, etc. When putting hand upon while blower working, one actually feel the suction so, they probably reduce air flow coming in (which is a much better option than letting spiders coming in). This is obviously not applicable to the recirculate mode in which there is no such obstruction.

So, back to why this is felt more when AC is on, I think running AC on recirculate for, say half an hour, which sucks humidity out, dripping from the car, followed by allowing fresh humid air to come in, humidity condenses on evaporator and causing some kind of temporarily obstruction. Also, the humid air came in will sure make one feel air flow is reduced similar to what happens running a home desk fan in humid weather, one has to bring it closer to face to feel it's producing air which is different than dry weather.

So, how about what I suggest that it's mainly the effect of those windscreen intake grills obstruction?

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Saturday, July 13th, 2019 AT 7:27 AM

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello again,

No, I don't think so. The air pressure alone at vehicle speeds would negate that. The simple fact is that the Air Conditioning unit will not be doing it's job if the HVAC unit is taking in outside air instead of re circulating it. If fresh hot air is coming into the cabin and the A?C is on it would be like having the front door to your house open with the A?C running trying to cool the house. Basically your trying to cool the outside, which will never happen. Please, if you have any other vehicle related questions, feel free to ask.

Thanks,
Alex
2CarPros

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Saturday, July 13th, 2019 AT 8:16 AM