Thread: Air con wars

When you set max cold (or Max heat) climate control does not work and you just get full heat or full cold as selected.

In theory you are correct but the reality is that temp is lowered quicker if full cold is selected. I wish there was an internal temp display because I find that the temp in the cabin rarely ties in with the temp selected even after being in the car for some time. I find the temp inside is normally warmer than that selected.

Garry

I think there is a maximum differential of about 6deg between each side too.

Every car is the same, it doesn't matter if it is 23 or 16, the car will pump out the coldest air until it reaches the selected temperature, or conversely warm air in winter. I leave mine on 24 on hot days because I dislike the AC fan blowing flat out all the time. The reality is that the cabin will never get to 16/21 on these scorchers and the AC doesn't have to work as hard to bring temp to 24.

Assuming a single speed / capacity compressor & a fixed expansion device such as a capillary or orifice, I believe that the refrigerant mass flow rate through the system will be fundamentally similar. Ignoring possible effects from external conditions, all that putting the set point lower achieves is a longer run time for the compressor & condenser fan as it will be trying to achieve a temperature lower than what you need.

Basically, with a simple system like above (pre inverter era split a/c being a prime example) there is only one possible speed - flat out.
Likened to driving a car on a journey. A-B.
By dropping the set-point, you are not 'accelerating the car' as it can only travel full speed. What you are doing is introducing a destination 'C' which is at some point beyond 'B'. So you are lengthening the journey, not reducing it or the time taken to reach 'B'.

If the D3/4 system is similar to D2,(which i think it is)the compresser runs most of the time using dampers and hot air to keep the climate inside the vehicle constant.

Back to the OP,if set on 16 it will run flat until it gets close to the setpoint and then modulate.If set on 21,it will also run flat out until nearing set point,then it will modulate dampers to keep the temperature correct.

So if you get into the vehicle and the internal temperature is say 30degrees,both sides will run flat out until nearing setpoint.Neither will cool any quicker.

If you get in and the temp is 20degrees,the side set at 16 will run flat out until it gets to around 16(if it ever gets there) and then modulate.The side set on 21 will probably heat slightly.There is are also other sensors as well such as light/solar sensors that come into play as well.

Hope that has helped.

Ratel10mm Can you put that in plain english please??

The D3/RRS is not a simple system as it is computer controlled with various sensors including a light sensor - the system tries to anticipate how hot or cold you might feel and compensates accordingly - eg if there is brilliant sunshine your body feels warmer so the A/c makes the system a little cooler than what is set - the reverse applies when the light sensor reads less light. Also the system does not just run flat out when the temperature is different to that set - when the difference is great the system works harder and as the actual temp gets closer to that set the system slows down. Simply - if the inside temp is 21 and the temp is set to 17 the system will run flat out, if you set it to 19 it runs at a much slow speed.

Garry

The Maximum differential in temperature between the two zones is 4 degrees. In my experience I have observed :

-that the system never blows flat out if the two zones are set quite differently.
-I think there is only one temp sensor at the front of the cabin (drivers side) so when the temps are set with a large difference, this sensor seems to be ignored and the two sides blow air at the required temp (with in 4 deg) but at a constant medium fan speed. Maybe there are temp sensors in the zones ducting?
-rate at which the fan blows is dependent on how close the cabin temp is to the zones temps
-Both zones always blow at the same fan speed

If it is a hot day I will blast the car with cold air to get the temp down more quickly and visa versa for cold days. Otherwise I let the car do its thing. If the two zones are similar in temp I think the car can do a better job of managing the temps as it is not trying to do a compromised job by trying to satisfy two very different settings.

Anyway... seems to be what I have noticed - not sure that it helps you in your quest though......good luck!

All good info

Now I need to figure out how to prevent certain radio stations getting tuned in