[tez]

We found the air con temperature in our new i30 rather too cold for comfort, particularly on long trips.
Obviously we have a base model without the (expensive) climate control option.

What I wanted was a way of setting the working temperature of the air con to be at a higher temperature than the default.

There is a simple mod that allows you to adjust the working temperature of the air con.

The air con temperature is controlled by a thermistor located in the air flow from the cooling element to the fan in the cabin.

At room temperature the thermistor has a resistance of around 10k Ohms, and this rises to almost double this value as the temperature of the cooling element drops to the minimum that the air con can produce.

The modification is to simply add some resistance in series with the thermistor, so that the air con control unit thinks it has reached its working temperature, but at a higher cabin temperature.

I added a 10k Ohm potentiometer in series with the thermistor.
When set to zero, there is no change from the original.
When set to full (10k Ohms) the air con operates at a minimum, reducing the cabin temperature only slightly.

Obviously you can adjust it to anywhere between these two extremes.
Call it a poor man's climate control. But it is very simple and reliable.

This mod has the side effect of the aircon using less power from the engine, so may produce some improvement in fuel consumption.

It has also been reported that EGR operation on CRDi models is reduced when the aircon is operating, so there may also an advantage in being able to operate the aircon virtually all the time without freezing and using power from the engine.


HowTo: The thermistor is located on the aircon assy on the RH side of the centre console  - you can see it on the exploded view on the web site below - it is shown as Part No. 97614H  in the lower right hand corner of the picture.

    http://www.wholesalehyundaiparts.com/showAssembly.aspx?ukey_product=8634315&ukey_assembly=1109580

There is a cable with two wires (orange and black) going to the thermistor connector. I cut the orange wire and connected the two wires from 10k pot. I mounted the pot on the side plastic skirt of the centre console just ahead of the transmission selector,  where it is convenient to reach down to it from the drivers position. I avoided mounting it in the dash panels where there are air bags and other stuff all around.

 
I hope this info is of use to someone else. Enjoy!


PS The same mod can be used on Toyota and Mazda, but the required resistance is only 2k Ohms, at least on the (mid 2000s) models I have fitted it to. Just check the thermistor resistance at room temperature.

 

 

[Dazzler]

  and 

Welcome tez

Concerning the air com temp, wouldn't turning back the dial of the temperature control have been an easier option

[tez]

If you mean the red / blue temp control in the centre of the console - what that does as I understand is to control the flow of hot water from the engine through the heater element in the cabin air system.

So if you run the aircon, and it is too cold, you can certainly add some heat from the heater to warm it up a little.
But it is not very efficient as the aircon continues to run at the normal rate (ie duty cycle).

By using the thermistor mod, the duty cycle of the aircon is reduced, thus reducing the power drawn from the engine and additional fuel.
And some wear and tear on aircon, belts etc.

This is the way that domestic aircon units control the amount of cooling. As anyone who has paid the power bill for an aircon house will tell you, winding up the cooling also winds up the power bill.

In winter / wet conditions in the car, using both warm air and a small amount of aircon together is a great way to keep the car de-misted.
You need only minimal aircon for this - just enough to pull some moisture out of the incoming air before it is warmed.

 

[Shambles]

Welcome tez and thanks for your very interesting observations


One thing confuses me, however.

When aircon is selected, the clutch on the compressor actuates to engage it creating extra load on the engine; the ECU compensates by adding extra fuel to the flow.

I'm mystified as to how any fuel savings can be made in the way you describe, given the compressor still has to be spun and the extra fuel is still injected  , unless of course the thermistor is there to deactivate the compressor clutch at a certain temperature? Hmmm.. must read up on this...

[Phil №❶]

Yes, the thermistor and it's added component, will cause the compressor clutch to disengage at an earlier stage than usual. Reducing engine load and fuel consumption.

[tez]

Further to Phil's comment, the clutch is only engaged for part of the time that the aircon is switched on.

The clutch engages to spin the compressor until the thermistor says it is cold, then the clutch is dis-engaged until such time as the thermistor says it is warm again.

It is exactly the same as the thermostat in your domestic refrigerator.

The ratio of on time to off time is referred to as the duty cycle. For a typical fridge, it is around 50%.

With added resistance to the thermistor, the duty cycle is reduced so that the cabin temperature is warmer than the original setting, and the compressor does less work.

[The Gonz]

Innovation of the best kind - simple and successful. If I had the cheapo system I'd be looking at this too. Well done, mate.

[FatBoy]

Really, what is the fuel saving going to be?  3/5ths of bugger all in my opinion.  Sounds like a good idea, but not really worth it IMO.  Modern AC units are more economical than older cars AC units.

[cruiserfied]

Sorry but i dont see any advantage by doing this.
The temperature is controlled by airflow routing not by coolant flow. The fuel saving i recon would be even less than Fatboy's prediction. Just a small adjustment of the temprature control would be adequate.

[The Gonz]

 

Back to the drawing board?

 

[ibrokeit]

However the comfort level is another factor.

[Phil №❶]

AFAIK, the compressor when running consumes about 5 BHP of energy to do it's job. So if you consider that bugger all, then I suppose it is.

As the refrigerant used in modern AC's is not an O₃ depleting substance, my understanding is that it is not as effective as the old R12, but safer for the environment, so how could it be more efficient.

Sorry gents, not convinced by your statements.

[FatBoy]

So that is about 4% of the car's available power (worst case).  They might use different gases which aren't as efficient, but like any newer product, the mechanical components (design, wear, etc) are more efficient.  You could have the same argument about modern cars using more fuel because the octane rating has dropped, however the design of modern cars means they are more efficient.

So if you used $100 of fuel a week, about 4% of that would be for the aircon.  Less than a cup of coffee!!

Not worth it IMO.

[Phil №❶]

I am not personally aware of any major design improvements that would counteract any gas inefficiencies, however, design improvements are always being made,  so I accept the logic of your statement.

BTW, great improvements have been made in electric AC. Using inverter technology AND strong Neodymium magnets in the compressor housing instead of wired iron core electromagnets.

[eye30]

My fd's air con was cooler than the gd's.

I'm told they used a different gas in the gd which does not cool as much as the fd