Air con testing?

Frozen_up_north

On a recent service, the dealer reported that the air con on my 2017 Seat Leon needed “topping up” and the cost would be £150 as the r1234yf gas is expensive.

Sensing a huge profit for them, I took the car to an independent garage that specialises in air con. They said the pressure was slightly low but should still have worked. They pumped out the gas, filtered it, and refilled the system. The full amount would have needed 460 grams of gas, they only needed 50g to replace the lost gas, ie there was around 410 out of a max of 460g in the system to start with. The bill was less than half the cost from a Seat dealer.

However, the air from the vents doesn’t feel as cold as from other cars, even though a test with a thermometer shows the vent air to be around 7 deg C, compared to a car with “colder” feeling air that measured 11 deg C.

I am puzzled, the car with the colder feeling air definitely measured 6 degrees higher air temperature exiting the vents.

Anyone with experience of car air con care to share their thoughts?

EssexExile

Perhaps the air movement isn't as fast, turn the fan up.

Frozen_up_north

EssexExile said:

Perhaps the air movement isn't as fast, turn the fan up.

If only it was that simple... it’s as if the air isn’t losing the moisture, so not feeling as cold regardless of the thermometer reading.

facade

The "R1234yf is expensive" thing is a rip-off, if you buy it in 5kg bottles from BOC it is £366.66, which works out at 7.33p a gramme (about twice r134a).  

Feeling cold with your hand is subjective, depends on how warm you are and the airflow rate giving a wind chill, the thermometer is the best test, but remember with "climate" as opposed to "air-con"  the flow rate goes down, and the temperature goes up as you get near the set-point and start mixing, and the temperature of the inlet air matters too- which is why they suggest max cooling is on recirculate.

daveyjp

How did Seat know it needed topping up?  They didn't so they were looking for work.

However, If it was cold before Seat said anything I would have left it well alone.

facade

daveyjp said:

How did Seat know it needed topping up?

Because it is 2 years old, and air-con systems always leak a small amount

fred246

I took my 2004 VW to an air-conditioning specialist for a regas in 2010 before a Grand European Tour. Cost £50. They didn't seem to add much. I returned in 2019. They were moaning that 9 years was too long. However, it had hardly lost any refrigerant and it cost £60. Both times it didn't seem to make any difference to the cooling. I quite liked talking to them because they actually understood what they were doing.

mcpitman

facade said:

daveyjp said:

How did Seat know it needed topping up?

Because it is 2 years old, and air-con systems always leak a small amount

Best get mine topped up/checked then - 10 yr old car, owned by me for nearly 7 years and never touched it.

I thought Air-con was a sealed system, so a leak is a leak which could be terminal?

facade

mcpitman said:

Best get mine topped up/checked then - 10 yr old car, owned by me for nearly 7 years and never touched it.

I thought Air-con was a sealed system, so a leak is a leak which could be terminal?

There are leaks and there are Leaks

Will be mostly slight porosity of the flexible hoses I'd have thought, then the rotating seal at the pump.  Mind you, the metal pipes are so thin walled nowadays I wouldn't be surprised if refrigerant could migrate though them

https://support.accuvio.com/support/solutions/articles/4000040366-annual-leakage-rate-for-the-refrigeration-air-con-hvac-

Ditzy_Mitzy

Frozen_up_north said:

EssexExile said:

Perhaps the air movement isn't as fast, turn the fan up.

If only it was that simple... it’s as if the air isn’t losing the moisture, so not feeling as cold regardless of the thermometer reading.

Did the air coming from it ever feel satisfactorily cold?  And how old is the other car you tested?  I only ask because my car, which is much older than yours, has an air conditioner that pumps out very cold feeling air, but isn't actually very efficient when it comes to cooling the cabin.  The icy blast sensation, which characterises air conditioners of yore, is a product of them being a fairly blunt instrument - they chill the air and suck the moisture from it.  A lot of people, me included, find it quite unpleasant and find ourselves loath to use the air conditioner, given its tendency to lead to dry eyes, skin, and headaches.  It isn't, necessarily, good to spend long periods in aggressively dehumidified conditions.  This link:
https://www.seat.com/car-terms/h/humidity-sensor.html
suggests Seat have attempted to tackle the problem by installing a cabin humiditiy sensor and giving the air conditioning system the ability to monitor and maintain a specific humidity level.  I'd expect that, in practice, such a system does a lot to blunt the harshness of the air output from the air conditioner without reducing overall efficiency; but the product of blunting the harshness is the loss of the old, familiar feeling Arctic gale. 

Frozen_up_north

Thanks Ditzy, I think you have probably hit the nail on the head. The cars in question are a 2017 Leon with climate control and a 6 month old Ibiza with more basic air con. The Ibiza feels noticeably cooler, even though the measured air temperature is a lot higher.