Efficient use of A/C

[Imuya]

yeap, that's why some people recommend doing the air-con mod. So even at the red zone the air is still cool, and at the blue zone it's colder than normal.

I forgot the exact details of the procedure, needs to reroute the coolant so it does not pass through the radiator i think.

Genie can clarify?

[Genie47]

Different A/C system different. Mine at centre (mix of blue and red) is already maintaining bare minimum by dehumidifying. As long as it is in the blue sections even the last blue section it is cooling AKA refrigerating the cabin.

 

You got to play around with yours. I already fine tuned mine for morning cool air as this:

 

Temp control to last blue bar before they mix with the reds. Fan speed to max (4) in the beginning. Open vent

 

Temp drops in cabin, I reduce fan speed to 2 and move temp control to middle (12 o'clock) that has a mixture of red and blue bars. Of course close vent.

 

Temp drop further, I reduce fan speed to 1.

 

From this time onwards, I play around with fan speed.

 

For hot afternoon parked in MSCP.

 

Same as above but I don't play around with temp control keeping it always at the last blue bar before the reds. Only fan speed.

 

For hot afternoon out in the sun, temp to max, fan to max, windows down, vent open. Cools quite fast and when things get better, windows up. Get even better, close vent. Much better, temp control to last blue bar before the reds. Finally fan control.

 

I got about doing this from observing my home A/C on sleep mode. First the A/C blows hard and the air is cold. Then when the temp became better, it slowed at the same time the air reduced increased its temperature. Finally it blew very slowly and the air is "dried" only instead of cooled.

[Cyberet]

hehe, bad point i heard about that is, no control over the temp.. even all the way at red zone also cold, the driver had to manually turn on/off the AC button on his way up n/s

Edited September 7, 2005 by Cyberet

[Genie47]

Yes, some A/C systems have dual function including heater. Mine is one of them. Go to far into the red zone and you get warm air blowing out. Mine around 12 o'clock still blowing out cool air. Actually not as cold and I suspect it is only dehumidying.

[Elfenstar]

Yes increase the temperature. I am assuming most of us have A/C systems as opposed to climate control system. Climate control system lagi best. Set temperature and play around with fan speed only but climate control system more expensive to service.

 

/me post whores.

 

Me, I've got climate control Winter is over and its the start of spring here in melb. Temps are also starting to go up at the same rate fuel prices are Any advice with regards to saving fuel with that?

[Genie47]

Set temp control to 23 deg C then play with fan speed. If really kiam, 24 or 25 is nice but may not cool fast enough. For efficient cooling and comfort plus less killing fuel bills, 23 is good. Again, if you can control the vent, do it. Open it initially and then when it gets cooler, close it. Windows are the last resort if it is too hot.

[Dennisk]

for every morning start is not advisable to on the a/c straight away right? then how about on the fan but A/C off?

[Genie47]

Then might as well not turn on the A/C when you start!

 

Seriously, I do it because I want the A/C system primed and cooling the air as soon as I join the main commute road. The cabin must be cool in the fastest possible time with mainly dehumidifying to maintain the temperature.

 

Another factor to load the car is my desire to give the engine a load to warm up and get off the startup cycle. My oil is thin and does not produce heat from shearing as compared to thicker 40 or 50wt oil.

Edited September 7, 2005 by Genie47

[Cyberet]

when u mean fan, u only refering to the cabin fan right? not the one in the engine bay behind the radiator right? when the radiator aircon fan turns on, is it an indication the compressor is working?

[Genie47]

Yes. The cabin fan draws negligible power. At normal expressway speeds, it is most likely the compressor fan is not working. Your speed is pushing 80-90kph "winds" into it. The compressor fan is peanuts compared to this. That is why I rather have it working hard when I start off on the road, then when things are hunky dory in the expressway, I lower all the settings because the "winds" provide much assist in the heat removal from the evaporator unit.

 

Explains why I avoid congestion areas. Low speed, low A/C efficiency which means I will have to set it more to cooling and increase fan speed. This makes the compressor fan kick in more often (cycle more) and need more power.

Edited September 7, 2005 by Genie47

[Cyberet]

ic.. haha..

 

i too turn on the aircon after all the warning lights goes off, need to warm up the car fast.. so my water temp hits operating temp before i enter expressway

 

car feels like lunging forward and auto gearbox also retarded first thing in the morning.. need to warm them up fast.. hehe

 

on a hot day.. my aircon is only cool when i hit the expressway

 

suana ah!

[PointyEwe]

A car air con compressor is only able to work at 0% or 100%.

Of course there are compressors that could work at part load very efficiently, at 0.1% to 99.9% load, but these are only industrial scale compressors.

 

For our cars, once the preset temperature is reached, the thermostat would:

1)Cut off compressor.

2)Hence resulting in the rise of cabin air temp.

3)Once the temp goes beyond the preset temp, compressor kicks in to start cooling again.

 

NOTE: Frequent cycling of the Compressor between 0% to 100% is most likely to shorten its life span than a compressor working at 100% at all the times.

Due to my personal beliefs, my air con knob is turned to the coolest since day 1.

 

For automatic temperature control to work, I reckon there's 2 way to go about doing it.

1. Fan speed remains constant. Solenoid control valve to regulate refigerant flow. Low flow, low delta-t.

OR

2. Fan speed varies automatically to match the preset temperature. Higher fan speed, higher delta-t (up to certain in limit.)

 

I suppose controlling fan speed is much better and easier than controlling refrigerant flow, hence most climatic control comes with option 2 instead.

 

Disclaimer: I don't work in the air con or car industry, so the above are just my thoughts.

[Achtung7]

Frequent cycling does shorten the life of the compressor... but letting your compressor run full time will also work the compressor till it's lifespan in a shorter period. Usually, 3min cycle is considered acceptable.

[Achtung7]

The dehumidifying occurs as a result of cooling. Air passes thru the coils which are at a lower temperature than the dew point of the air and hence vapour condenses on the coil. Thus you get air that is cool and dehumidified. Once the compressor cycles off, the coil surface temperature rises and the air isn't dehumidified.

[Huggable]

When the engine is turned off, the battery will have to power the electricals like clock, and car alarm. The battery only gets charged when the engine is turned on the next day, ie when the alternator is on. It's not advisable to load the battery right away when you first start the engine as it might result in insufficient charge, and shortened lifespan. Same for the car headlights, I never turn them on the moment I start the car at night.

 

Normally in the morning, I don't turn on the air-con if I don't feel warm in the car. I'll leave the fan and a/c off, and turn off the re-circulation, wind will come into the cabin as the car moves. The sunroof will be open if it's not raining. For the windows, I noticed that instead of winding down the driver's side, you'll actually feel cooler if you wind down the front passenger window! Try it...

 

for every morning start is not advisable to on the a/c straight away right? then how about on the fan but A/C off?

[Freakman]

for mine understand from my mech that the previous owner has done some fix preset tuning so so-called... so cant do any adjustment to my A/C... it will always maintain that specicfic temperature... so in the morning cold like sotong... noon hot like drunken prawn... only thing can adjust is the fan speed.. but then again i am driving a small cc car.. so A/C bo lak one la...

[Genie47]

Chevy A/C's cycle. They never cut off like the older cars. This also explains their high FC.

[Elfenstar]

Actually thats wrong when it comes to car batteries. They will last longer with a sudden high drain and than with extended low drain scenarios. A slower charge rate to the battery also increases it life as opposed to a higher charge rate.

 

Also you car should not be running off the battery when its on, all power should be drawn straight off the alternator while its running. Car batteries are not desgined for long slow drain applications and slow charging decreases (even reduces if slow enough) the sulfate buildup on the plates.