Automotive climate control

[BobT]

After starting a different thread about my truck thermostat, I decided to start this discussion. I bought my 2001 F-150 new in the fall of 2000. I have been very pleased with this truck all these years with maybe two exceptions. I’ll talk about one of them.

Probably my most prominent disappointment with this vehicle has been climate control. Don’t get me wrong. It works but just not up to my expectations. The cab heater has never really put out the kind of heat I have come to expect from my vehicles and I have not been impressed by the A/C either. I rarely use A/C because I don’t care much for conditioned air but on those occasions when I have used it, it really came up short.

Be that as it may, one feature that many manufacturers employ is to program the A/C compressor to engage when blend or defrost positions are selected. In other words, if you want to move air across your windshield, it will be conditioned. In the fall when the outside air isn’t hot, I like to use the blend position to defog my windshield but I don’t like the idea of wasting gas to run the A/C compressor. I’m not looking to cool my cab, just defog the windshield. Besides, the colder air from the defroster now causes condensation on the windshield, which is what I’m trying to eliminate by having the air blowing on the windshield in the first place. To counter this effect, I’m forced to turn up the temperature setting of the defroster. It’s like running your furnace and air conditioner at the same time.

I have been told that the reason for this is so that the compressor runs occasionally throughout the winter months to help keep things lubricated. I have a hard time buying the lubrication theory. I have some window air conditioners that we occasionally use during the hottest summer days. They are used just for a few nights from maybe late July through August but then sit idle for ten months of the year. I don’t plug them in and run them occasionally throughout the winter and yet they fire up and work just fine year after year. The same is true for our basement dehumidifier, which sits idle for about 8 months every year. I have never had a problem with these units.

Another reason I don’t buy it is because my 2001 Chrysler gives me the option to turn my A/C on at my discretion. The compressor does not run simply by selecting the blend or defrost positions and yet the system works just fine when I need it.

Can’t we end-users at least have one position where we can move natural outside air across our windshield?

Bob

[fishhuntwork]

That is not true you chrysler compressor does run when you turn your defroster on. Being a former dealer tech, chrysler has numerous issues with its air cond. and it is true about the luberication issues. That is the main reason they do kick on with the defrost.

[Jeremy airjer W]

Your home equipment isn't subjected to the extremes that you vehicles equipment is subject to as well. Just the temp extremes they are subject to makees you wonder how they last as long as they do. Then add the fact that the compressors are slammed on at any number of different RPM's and they are subected to engine and road vibrations and there starts to be a huge difference in between the two systems! Then account for the rubber hoses and all of the gaskets that need to be used to make it serviceable and to account for engine/body movement and they will not be anywhere near as reliable as your home system. Although some manufactures have nailed reliability on there HVAC system, many have not!!

The conditioned air is dry air so it helps defog a windshield that much faster. I think you will find that most newer vehicles will get at least the same or better fuel economy running the a/c as they would with the windows down. I don't think fuel economy is as good of an argument as it once may have been.

[Scott K]

I agree with what was said. If your looking to add to your economy, you would have to drive with your a/c off, and your windows up, not easy to do in the summer. I am pretty sure all models from the 90's until today cycle the compressor atleast for all defrost modes, and for two reasons. One, just to cycle the compressor and the oil into the entire system, to run the clutch so it doesnt just build up with rust, and as Airjer said, the evaporater removes moisture from the air in temps above 35 degrees, to assist in defrost mode.

[BobT]

The temperature extremes and weather, moisture, snow dust, dirt, etc. would promote issues that I didn't consider with my window units. Good points. Cycling the unit throughout the winter occasionally through the defrost selection is one way to do it so we don't forget to do it ourselves. Okay, makes sense.

I still have a problem with air conditioned air at moderate temps. What I'm referring to are those times when it's 60 degrees outside and humid and all I need to is to move some outside air across the windshield to defog. Outside air will do this just fine. When the air conditioner starts to pump out cold air at 50 or 60 degrees it causes the window to get cold and that's what caused the window to fog up in the first place. Being of the type that prefers to avoid conditioned air because it bothers my sinuses, I'd rather use outside air to do the job.

This is when I think it would be nice if the compressor only cycled automatically in defrost mode but not in blend mode.

Bob

[Scott K]

About all you can do is unplug the compressor.

[fishing tech]

Disconnect the low or high pressure switch and then don't complain when the front seal on the comprssor leaks and you have a bigger bill to pay. I have an 01 supercrew that throws heat to no end. You may have a blend door problem if you are not getting enough heat.

[JollyT]

Also, remember the heat is waste heat anyway. If it isn't going into the Cab, it's going out the radiator. The AC is the only excess. But the AC running also drys out your carpet and interior much faster when you get it wet or snowy.

[deadeye]

Sounds like you need to upgrade to a 1974 model !

Just open the wing windows and it is all good.

[BobT]

Sounds like you need to upgrade to a 1974 model !

Just open the wing windows and it is all good.

Now that's the best statement I've seen yet.

Bob