The 08 allows the user to manually set the blend door as described by Mark for the prior years. The temperature control automatically adjusts the fan speed to maintain the cabin temperature. This does provide some relief on compressor load, as the refrigerant gas is less dense and easier to compress when it picks up a smaller amount of thermal energy from the cooler cabin air.

But, cyclig the compressor should save more, probably at the expense of lower mechanical component life.

 

Yep it will definately wear the compressor clutch out. But if cycled slowly this could be kept to a minimum and last 150,000 mi. What really wears the compressor is the on off cycle of a low system, which can be as quick as every 15 seconds.

 

Mark, I don't think elevation is a major factor.
I drive in Denver, Los Angeles, Omaha, Chicago, Las Vegas, and everywhere in between. My A/C compressor has always cycled frequently.

When I lost the charge of "freon" it then would come on and stay on because it would never get cold. Took it to a large Ford Dealer just a few months ago, and they fixed the leak and recharged the system. Now, mine gets very very cold, very very fast.

Is is possible to have too much 134a in the system?
Is it an advantage to bleed some off?

Either yours is broke or mine is.
Mine was just serviced 3 months ago by a large Ford dealer in a large city.
???

 

Thank you all very much.

Salsbr – The A/C switch is really what I was looking for.

Mark – I really like the vacuum idea as well. I’m not sure which I will go with because I have one final question before I begin.

Salsbr – With the control **** in the defrost position and the A/C switch off, would this allow the vehicle to go in to EV mode?

If not, then I may have to go with a “hybrid” approach and install the A/C switch (because I am a control freak) and also play with the vacuum.

Thank you all again very much and I look forward to your reply.

 

A/C systems like ours use a low pressure cut off switch that is supposed to be set to turn of the compressor at 29 psi which coresponds to about 33 deg F. Now the system will go that low when the temp of the air moving across te evaporator is fairly cool and DRY. Humidity plays a very BIG roll in A/C performance. This is why there is a normal and a max setting. The normal setting takes outside air and cools it through the evaporator. The max setting recirculates the inside air. Max is for high humidity areas otherwise it is VERY difficult to get the duct temp below 55 deg, which is usually the dew point. Now your a/c system might be fully charged and cycling IF your outside temp is low 90s and you humidity is 40% or lower. All of the areas you mentioned are cool DRY areas compared to the gulf coast. Our systems also have a high pressure cut off switch but this is used to protect the compressor if the system is overcharged or the radiator fan is not working. As a test to see if your a/c is cycling correctly use the normal setting and see if the compressor runs for a longer period. Now IF you have a way to measure the temp of the hose coming out of the compressor and the temp of the hose going to the accumulator bottle from the evaporator and the air temp I could most likely tell you if you are overcharged. Undercharged is a little more difficult really need pressures and duct temp on max with high blower. The new r-134a freon is really difficult to judge by pressures, I much prefer to recover the freon and weigh it then charge with a know weight spec'd for the car. And is almost imposible to service when the temps are below 65 deg because you can miss the charge weight by as much as 1/2 lb. Why I dont know, but I think it has something to do with the viscosity of the r-134a. HTH

 

Only if it is overcharged. If your system is cycling allot you will wear out the compressor clutch. Also I have been noticing the chirp and I think the compressor comes on any time the ICE starts then almost immediately shuts off. Are you seeing this? Also how is your compressor led wired?

 

The A/C Clutch is programmed to spin for the first 1/3 of a second every time the car is started to purge any liquid than may have accumulated in the compressor. I assume this means once every key start, and not ICE start, but I'm not sure. I'll look for the reference.

you are right.
Today in Colorado the dewpoint is 17 degrees.
However, at my other home in Minnesota, last week, the dewpoint was as high as 65 degrees, and still.... my A/C cycled often.

I tapped the 12v supply wire to the A/C clutch and installed a 12v red LED on my dash. But if you don't have that, you can hear the engine lug down each time if you are standing still and engine is as idle.

I put it in primarily so I could monitor when my HV battery got above 85'F and requested A/C cooling. With 10% humidity in Colorado, I can do ok with windows down most of the time. However, since I use "hypermiler" techniques to get 54+ MPG in the city, my battery gets hot enough to require A/C even on 50 degree days. -John

 

"I tapped the 12v supply wire to the A/C clutch and installed a 12v red LED on my dash. But if you don't have that, you can hear the engine lug down each time if you are standing still and engine is as idle." - gpsman


gpsman,

Where is the easiest place to tap the 12v to the A/C clutch wire when installing a LED in to your dash?

 

I ran a small wire under the hood to the A/C clutch itself, then ran the wire through the firewall near the steering column.

 

Since we can finally post again...

If you look at the first post of https://www.greenhybrid.com/discuss/...-hybrid-13755/

you will see the schematic of the function selector switch. There are three electrical outputs in addition to the not shown mechanical switch for the vacuum system.

These outputs are:
ACRSW - Recirculate Selector.
ACCS - AC Request
ACFDS - AC Force Request

Of course I'm making up the names above, but AC Request is used to request the AC, but not force the engine to remain on. AC Force Request forces the engine to remain on so the compressor can run.

If all you want is a switch, you can simply cut the ACCS and ACFDS wires, and attach them to switches as appropriate. A good place to get power for the switches is the fourth output, the BR-YE wire. This way power can only be applied when the selector switch is not set to off.

I suppose as an alternative you could simply run these wires through a switch and either connect, or disconnect them depending on if you wanted AC. That might be easier.

As long as the ACFDS wire is off, the engine will not be forced on.

Hopefully that answers your question.

-salsbr