To air con or not to air con

[White beast 2023]

Hot days yes, average days not really

 

[J_D 2.0]

IIRC, VF has a function to do something similar automatically ?

And there’s no reason that Holden/GM couldn’t have made that feature available in VE‘s as well through a firmware update, after all the entire HVAC system in the VE is electronically controlled by the computer as well but car manufacturers shitfuckery being what it is….

 

[someguy360]

Theres a reason climate control systems turn the compressor on automatically even when heating.

It's called air conditioning not air cooling, it's designed to regulate the air to the right conditions not just to cool it down. On my VE the climate control system automatically runs the AC compressor even if it's 2 degrees outside as the compressor is also used for defogging the windows. Most automatic climate control systems will use both the heater core and the AC compressor to balance the quality of the air delivered inside the cabin at the same time.

The reason windows fog up is due to condensation/moisture inside the car which is hot (it's what your body expels) and the outside of the glass is cold the air conditioning removes the moisture in the cabin while at the same time the heater core provides the warmth you need.

Theres a reason window fog gets worse when you turn the AC off and blast the heat at the glass......all your doing is creating more moisture inside the cabin and pumping it at cold glass, which creates fog.

Most people don't understand that air conditioning in a car is designed to do a lot more than just keeping the driver cool. So realistically theres no reason in 2023 why you shouldn't just leave the AC on year round and let the temperature settings do it's job. Theres no noticable power loss or fuel economy difference these days like there was 30-40 years ago. The added advantage is you are keeping the AC system healthy at the same time as it lubricatres the system as it runs.

I remember my old XD falcon would almost stall when you turned the AC on back in the day the compressors were that inefficient, thats simply not the case anymore. It's very old school and outdated thinking to only engage the AC compressor when it's hot.

 

[J_D 2.0]

Theres a reason climate control systems turn the compressor on automatically even when heating.

It's called air conditioning not air cooling, it's designed to condition the air to the right conditions not just to cool it down. On my VE the climate control system automatically runs the AC compressor even if it's 2 degrees outside as the compressor is also used for defogging the windows. Most automatic climate control systems will use both the heater core and the AC compressor to balance the quality of the air delivered inside the cabin at the same time.

The reason windows fog up is due to condensation/moisture inside the car which is hot (it's what your body expels) and the outside of the glass is cold the air conditioning removes the moisture in the cabin while at the same time the heater core provides the warmth you need.

Theres a reason window fog gets worse when you turn the AC off and blast the heat at the glass......all your doing is creating more moisture inside the cabin and pumping it at cold glass, which creates fog.

Most people don't understand that air conditioning in a car is designed to do a lot more than just keeping the driver cool. So realistically theres no reason in 2023 why you shouldn't just leave the AC on year round and let the temperature settings do it's job. Theres no noticable power loss or fuel economy difference these days like there was 30-40 years ago. The added advantage is you are keeping the AC system healthy at the same time as it lubricatres the system as it runs.

I remember my old XD falcon would almost stall when you turned the AC on back in the day the compressors were that inefficient, thats simply not the case anymore.

Most cars now have variable compressors that vary the refrigerant flow depending on the specific requirements. The design of which is pretty ingenious and does a lot to improve the efficiency of automotive HVAC systems.

 

[someguy360]

Yeah it's amazing how far compressor technology has come since the turn of the century.

Most cars now you wouldn't even feel/hear the compressor engaging/disengaging. Back in the day on the old 1st gen commodores, kingswoods, falcons etc when you pressed the AC button you'd know about it.

The engines RPM would drop dramatically, you'd hear a huge clunk as the compressor engaged etc and you'd feel about 10kw instantly wiped off.

 

[losh1971]

Series I VE have fairly poor AC for a modern car. Not sure if they improved it with Series II?

 

[someguy360]

Series I VE have fairly poor AC for a modern car. Not sure if they improved it with Series II?

S2 worked beautifully.

I had a S1 WM and I agree it wasn't the best.....the S2 cools the cabin in about 2 mins even on a 40c day.

The only downside to the S2, and I've seen some others complain about it as well, with a stock exhaust the compressors can be a bit noisy (a bit of a whirr/groan you can hear in the cabin)

 

[losh1971]

S2 worked beautifully.

I had a S1 WM and I agree it wasn't the best.....the S2 cools the cabin in about 2 mins even on a 40c day.

The only downside to the S2, and I've seen some others complain about it as well, with a stock exhaust the compressors can be a bit noisy (a bit of a whirr/groan)

Yeah, I have to set mine on 15deg or its just not cold enough in the summer.

 

[Fu Manchu]

Series I VE have fairly poor AC for a modern car. Not sure if they improved it with Series II?

in 3 years, they will be 20year old cars.

 

[Skylarking]

Series I VE have fairly poor AC for a modern car. Not sure if they improved it with Series II?

AC works by compressing a specific gas to a point where it can turn to liquid as it looses its heat while passing through a condenser. Then when this liquid expands within the evaporator, it takes heat from the surrounds. This is also why the pipes after the condenser are smaller than the pipe after the evaporator.

The really interesting part is what pressure it must be compressed to, what size the condenser must be and what size the evaporator must be for it to all work well.

The pressure really depends on the type of refrigerant gas used which is why all compressors fundamentally produce the same pressures when running the same type of gas. But the condenser/evaporator sizing really depend on the ambient temps the vehicle must operate within and you can see large differences in sizing between EU cold climate vehicles verses hot climate vehicles. (heck I knew of a guy who had a contract to replace condensers and evaporators within newly imported Merc commercial vehicles so they can operate effectively within our Aussie hot climate conditions). It’s a bit of a balancing act getting the sizing correct.

Really how AC works is based on the second law of thermo dynamics and covered by the combined gas law of PV =nRT (and probably other laws related to fluid flow and heat transfer through radiators). In days gone by i‘d have been able to do the maths to confirm correct sizing but these days I’m pressed to remember 2/3rds of what I was taught…

In any case the maths isn’t needed as it’s all been done by the manufacturers and any Aussie vehicle who’s AC isn’t performing well is doing so because of a failing compressor, a blocked condenser or blocked evaporator, being low on gas, etc. The other issue could be contaminated refrigerant gasses from dodgy servicing at some stage in a vehicles life but any honest ac service guy will be able to sort it all out. Oh, and don’t discount a faulty temp sensor or two that is sending corrupted data to the AC module so the system gets faulty data and thus cant perform in an optimum way (i think the VE had a service bulletin to reposition the evaporator sensor to avoid ice us and loss of cool air).

So if your AC isn’t working well, start easy and as a first check ensure the evaporator is clean and clear of all rubbish and the fins aren’t pushed over thus blocking airflow. Doing the same for the evaporator isn’t so easy because of packaging issues (a design IMO). Then you can use an ac manifold gauge set to check high & low pressures are ok and if they are to use a thermometer and do a max cooling performance test using the tables that are within the service manual.

Doing such will highlight whether the system is performing within expected limits and whether the refrigerant cycle part of the system is working well. The computer control side is a more complex issue to test…

The other thing to keep in mind is that whenever coming from an older car with more upright windscreen and side glass with well working AC, any newer vehicle seems worse with AC as the newer body designs allow much more of the hot sun to beam through the glass and overheat some parts of your body while other parts that the AC blows cold air onto just makes it all uncomfortable… Older cars, especially those with more vertical glass and especially those with glass which reduced UV and heat transfer into the vehicle itself always felt much more comfortable.

It would be interesting whether there are iany differences in evaporator and condensor sizing between VE S1, S2 and VF…

But having companies go cheap isn’t so great as the HVAC electronic control side definitely got worse with VF as Holden pulled various temp sensors out of the cabin and duct work, instead using some bullshite algorithm to guesstimate cabin conditions, all in a vehicle that has sweeping front, rear and side glass…