AC in winter time

[musicaldoc]

Is there some automatic swithcing off of the AC under apx 41 F°??

I usually use the recirculate position with AC on, and when outside T goes down apx 41F° I get fog on the windows and can clearly smell high humidity in the air from the outlets.
To clear the windshild I then have to switch to defrost position.

Is it normal or do I have some problems with the AC?

 

[kjpilot]

Don't use the recirc setting. that will solve all humidity problems. All defrost settings turn on the A/C & so do the snowflake settings. Think about it, if you use recirculated air, you let in no fresh air... if there are any living, breathing creatures inside, they add moisture to the air that you are recirculating... as the warm moist air hits the cold windows the moisture condenses on the windows. Yes the A/C is running, but it can't dehumidify the air fast enough.

If you use fresh air, it has less moisture, & what it does have, the A/C largely gets rid of as it comes in, the stale moist air is displaced. Your Jeep will smell better too!

 

[musicaldoc]

yea, I understand, but in traffic I need recirculating, and the fogging (with noticable humid warm air) appears instantly, as if AC turns off automatically...

 

[kjpilot]

The things I described above cause all this to happen very quickly. But the A/C is not designed to turn itself off. Do you smell coolant when this happens? Or a smell like dirty gym socks? If not, it sounds to me like everything is working as it's supposed to.

Why do you need recirc in traffic?

 

[JeepJeepster]

I would say that the A/C is kicking off when its that cold. Its to cold outside for the A/C to be running in those temps.

It will kick on in defrost but not near as long as it would with it on the A/C setting.

 

[kjpilot]

I would say that the A/C is kicking off when its that cold. Its to cold outside for the A/C to be running in those temps.

It will kick on in defrost but not near as long as it would with it on the A/C setting.

Too cold??? 41F is shorts weather! (woot)

I've never heard of this feature. Why would it ever be too cold for the A/C to operate? Mine sure doesn't do that, & I run the A/C all winter long... down to -23F this year... now that's starting to get a little chilly.

 

[Ry' N Jen]

I can run my A/C with the heat cranked. That way the car de-fogs faster then if I were to run straight defrost.
I have this past winter run the A/C with the temp set to hot on defrost and have experienced just what you mention, excessive moisture and a dank smell.
I went to a marine supply store and purchased a container of "Dries the air"
A neat little device that has silica beads that absorbs like 10 times their weight in water and as the name sugests, it "Dries the air". Works very well.

 

[kjpilot]

I can run my A/C with the heat cranked. That way the car de-fogs faster then if I were to run straight defrost.
I have this past winter run the A/C with the temp set to hot on defrost and have experienced just what you mention, excessive moisture and a dank smell.
I went to a marine supply store and purchased a container of "Dries the air"
A neat little device that has silica beads that absorbs like 10 times their weight in water and as the name sugests, it "Dries the air". Works very well.

Yeah, that old gym sock smell that most Mopar A/C systems get eventually. That's from water getting into the ducts & causing mildew to form.

 

[JeepJeepster]

Im not an hvac engineer but since its alot cooler outside the pressure can get all messed up or the evap can freeze up.

When you use the defrost, the compressor doesnt stay engaged near as long and the interior is also alot warm which prevents the evap from freezing up.

 

[hyde]

You are lucky, at least yours if fogging when you turn it on. Mine used to fog when I didn't even turn anything on. I just hit the gas, windshield is fogging at the bottom.. Weird! Now it is fine, I guess because I have the heater on almost all the time.

 

[hyde]

Yeah, that old gym sock smell that most Mopar A/C systems get eventually. That's from water getting into the ducts & causing mildew to form.

We had a plymouth voyager, that was just possessed by the weird smell, we would almost puke because of that stink. We couldn't get heat, dealer couldn't find the solution.. We could only put 35k miles on that sucker in 8 years. Finally sold it, it went for $2500 against down payment on another KJ now my uncle is driving. Damn voyagers.

 

[kjpilot]

Im not an hvac engineer but since its alot cooler outside the pressure can get all messed up or the evap can freeze up.

When you use the defrost, the compressor doesnt stay engaged near as long and the interior is also alot warm which prevents the evap from freezing up.

While that may be an issue at some point of the temperature spectrum, it's unlikely it occurs at 41 F. I don't know what R-134a does temp wise, but freon gets very cold. My grandpa owned a TV sales & service business. Back before anyone was talking about holes in the ozone, they used to spray freon on circuit boards to find cracks. Being a nosy kid who, as the first grandchild, was allowed to roam free in the shop, I did quite a bit of experimenting with the freon

The cans said it froze things to -50 F. Of course the A/C system keeps things at a higher pressure than the open atmosphere, keeping the temps from falling that low, but it still remains quite low in the evaporator. If it didn't, we would not have freezers to put our ice cream in. By the way, if you flash freeze a grass hopper to -50, & then let it warm up it slowly comes back(naughty)

 

[tjkj2002]

You all need to understand what is A/C(Air Conditioning,not Air Cooling).A/c is not ment to reduce the temp of the air,it's a good side effect of A/C.A/C lowers the humity in the air which in turns cools it also as a side effect.Less humity means less vapor in the air to cause condinsation on glass and such and makes you feel cooler since when you sweat the conditioned air will evaporate your sweat faster making you feel cooler.

So don't b#$%h and whine when it's a 100 degrees outside and 90% humity and you don't think your A/C is working good enough.It's not ment to cool the air and has it's limits in high humity areas.

Oh the A/C system on your KJ keeps the temp at around 34 degrees at the evaporator to prevent it from freezing up,hence the clycling clutch on the A/C pump.Temp doe effect the system pressure only,hotter=more pressure,colder=less pressure.The act of the R134A(or R12) turning from a liquid to a gas state is where the cooling effects are felt/formed.

 

[JeepJeepster]

Yea, mine does that some too hyedipin. Im not sure where that moist air comes from but its kinda annoying. Usually only does it on a warm/cool day.

 

[kjpilot]

You all need to understand what is A/C(Air Conditioning,not Air Cooling).A/c is not ment to reduce the temp of the air,it's a good side effect of A/C.A/C lowers the humity in the air which in turns cools it also as a side effect.Less humity means less vapor in the air to cause condinsation on glass and such and makes you feel cooler since when you sweat the conditioned air will evaporate your sweat faster making you feel cooler.

So don't b#$%h and whine when it's a 100 degrees outside and 90% humity and you don't think your A/C is working good enough.It's not ment to cool the air and has it's limits in high humity areas.

Oh the A/C system on your KJ keeps the temp at around 34 degrees at the evaporator to prevent it from freezing up,hence the clycling clutch on the A/C pump.Temp doe effect the system pressure only,hotter=more pressure,colder=less pressure.The act of the R134A(or R12) turning from a liquid to a gas state is where the cooling effects are felt/formed.

I don't think anyone said anything about cooling the air in the car. We are talking about using the A/C in temps between 41 and -23F to remove moisture after all...Last thing I want is cold air.

The act of pressurizing a gas (any gas) causes it to heat, decompressing it causes it to cool. In a sealed system, like what the A/C system is, there exists a system pressure. As you know, the system works by compressing & decompressing the coolant gas. If atmospheric pressure is lower than the lowest pressure in the A/C system, the coolant gas cannot decompress as much in the system as it could in the open atmosphere, outside of the system. So if the gas cools as a result of decompression, decompressing to a lower pressure would allow it to cool more.

That is why I stated that letting the freon out to the open atmosphere would allow it to get colder than keeping it in the closed A/C system.

Edit: But FWIW, in the summer the A/C cools the air as well as dehumidifying it. Using it in the winter, you are using it as a dehumidifier... It is the dehumidification that is a useful byproduct of the air condidtioner, not the cooling.

 

[hyde]

Sometimes I just turn the dial to the center and ride like that (PS, on pre-05 we do not have seperate fan/AC button). It makes it easier to breath inside, if I have full house.

 

[kjpilot]

Okay, so I found this, It's not a function of how cold the coolant gas gets inside the evaporator, but moisture on the evaporator freezing:

EVAPORATOR

Located inside the vehicle, the evaporator serves as the heat absorption component. The evaporator provides several functions. Its primary duty is to remove heat from the inside of your vehicle. A secondary benefit is dehumidification. As warmer air travels through the aluminum fins of the cooler evaporator coil, the moisture contained in the air condenses on its surface. Dust and pollen passing through stick to its wet surfaces and drain off to the outside. On humid days you may have seen this as water dripping from the bottom of your vehicle. Rest assured this is perfectly normal.
The ideal temperature of the evaporator is 32° Fahrenheit or 0° Celsius. Refrigerant enters the bottom of the evaporator as a low pressure liquid. The warm air passing through the evaporator fins causes the refrigerant to boil (refrigerants have very low boiling points). As the refrigerant begins to boil, it can absorb large amounts of heat. This heat is then carried off with the refrigerant to the outside of the vehicle. Several other components work in conjunction with the evaporator. As mentioned above, the ideal temperature for an evaporator coil is 32° F. Temperature and pressure regulating devices must be used to control its temperature. While there are many variations of devices used, their main functions are the same; keeping pressure in the evaporator low and keeping the evaporator from freezing; A frozen evaporator coil will not absorb as much heat.

PRESSURE REGULATING DEVICES

Controlling the evaporator temperature can be accomplished by controlling refrigerant pressure and flow into the evaporator. Many variations of pressure regulators have been introduced since the 1940's. Listed below, are the most commonly found.

 

[musicaldoc]

Hi, I've been out town for a while and I have experienced again the issue in the mountains with A/C on and temp knob midway on recirculate with outside temp below 40F° (5 °C)

It must be something linked to outside temp, that's for shure. I do use the recirculate becouse I drive in very polluted areas and I use temp knob towords the middle with A/C on to get warm de-humidified air in the KJ.

As I posted at the beginning of the 3D it's cleraly noticeble the "heavy" smell of warm humid air, exactly the same wich comes out if I switch manually the A/C off during operation.

It can't be a pressure problem becouse the system would be kept "off-line" all the way and not randomly. I remember that on my old VW Passat was stated that the A/C was switched off automatically below 40F° to prevent freezing in the system, and I had the same "smell" too.

I have looked around the tubes in the engine but I haven't seen any freezing sign....don't know what to do over that I won't in any way let anybody mess around with my evaporator, removing all the dashboard...

 

[JeepJeepster]

Okay, so I found this, It's not a function of how cold the coolant gas gets inside the evaporator, but moisture on the evaporator freezing:

Yea, thats what I was talking about.

 

[musicaldoc]

So if the evaporator temp exceeds the 32° limit the clutch stops the compressor........did I get it?