Just got off the phone with an AC bud.

All condensors/compressors can only drop the temp 17-22 degrees across the coil, depending on the type of freon used. That goes for homes or vehicles.

There are many other variables like engine speed, size of pulleys, etc., that can spin the compressor faster or slower.

The other factor of how it actually feels is humidity. If you cool something too fast, it can't take out the humidity, so 75 can still FEEL like 95.

If you are going to post numbers to try and convince somebody of anything, you got to say whether your recircing the air or pulling outside air.

I'm not getting into it here, I'm trying to help. If you can post a link that says a truck AC unit can drop the temp across the coil more than 22 degrees, I'd love to see it.

Maybe I'll learn something.

The other point is to make sure are recirculating the air. That will cool it where you want it.

 

My 06 is going to have the AC looked at on Monday. I dont use AC alot but my wife did notice the Rams AC was'nt as cold as her 2001 Jeep Cherokee. Maybe mine is just performing as normal??? My Audi S4 will freeze you out of the car in 30 seconds or less in any heat. Do most of 2006 owners run their AC on recirculate all the time???

 

You have to think about the size of the area you are trying to cool.

A car is very small, a qc or mega cab is very large.

Try cooling off a bus that transports a bunch of people.

Those big systems on fridge trucks work the same. There is NO MAGIC.

All AC units work the same, there is no magic.

Then there are the revs that the compressor is spinning, depending on pulley sizes, rpms, etc. This only has to do with if it cools at idle or not.

Then there is the question, are you or anyone else bringing in the 100 degree outside air and trying to keep cooking it (the best you will do is around 80), or do they have the controls set to recirculate the inside cab/car air that is already getting cooled?


Jeeze, somebody said his air blow 40 degrees lower than the outside air, I dispute it. Unless he was recircing the air and had it running for a little while.

The other question is;

What kind of thermomoters are they using?

 

Thanks for all the great feed back, it's nice to have connections like your friend at DCX. You have gone out of your way, thanks a million!! Yes, the Mega cab has two vents at the bottom of the center console for the rear seating area.

For everyone else, before I even took the truck into the first dealer I documented everything and the conditions during the checks: This is very important and do your homework. When the first dealer told me he recorded 40 at the vents I said sorry no way. I have a thermometer in my console and I will check it on the drive home. I called him the next day with the "facts".

When I do my testing I follow the same test procedure.
1.The A/C is on recirculate-
2.Using a digital Blue Point A/C test thermometer. Verified in a 68 degree climate controlled inspection room. The therm has a 1 degree above actual error-
3.After all windows have been opened 5 minutes I turn the fan on high setting/recirculate and close it up.
4. After 5 minutes of driving, turn fan down one notch, you will notice a temp drop at the vents (center or drivers) of 2-8 degrees in 3-10 minutes. This is because you are allowing the evaporator to work more effieciently. Area vs CFM of air flow.
5. Record cabin temp at drivers head, rear seat and rear head rest. Cabin get abot 83 degrees at best, still warm for 5 people on a road trip!

I have owned several large vehicles (Ford van, full size Bronco, currently a Chev. Suburban) and have taken cabin size into consideration. Yes two vehicles had dual air, but even running with the front only it will raise the hair on your arms, it gets cold! Currently our 02 Suburban will freeze you out with only the front A/C. The Sub. is Indiglo blue (dark color) with a charcoal interior, it blows 48 degree air all the time 2-3 minutes after start up.

I will see what happens next week when they install the new and improve blower case. I will post the results.

Keep up with all the good info!!

 

There are elements of everyone being correct and wrong here.

Yes the QC/Mega are very large vehicles but, other large vehicles do not seem to have this "apparant" cooling problem with their respective AC units?

Also, comparing a QC/Mega with a Jeep Cherokee isn't exactly fair either. In that this vehicle is considerably smaller than the QC/Mega, therefore, there's a smaller amount of air/vehicle to cool.

But............at the end of the day, you can't argue with the fact that some equal size vehicles to the QC/Mega, seem to have this licked and CAN cool better than the Dodges..........
Hmmmmmm.
Al.

 

Mopar used to know how to get it right. The a/c in my `66 monaco will freeze you out of the car in no time and it has a really big interior space to cool. The `02 ram is just kinda` luke warm and I was quite dissappointed in it. I don`t think any of this new 134 crap cools as well as the old systems on R12.

 

The trick to cooling the air faster or lower is in the "size" as in btu's removed. Simply put, the systems in the rams are undersized. To remedy this would require an evaporator coil of more surface area, a condenser of more surface area, and a larger compressor. The 18-22 deg rule is correct, it's how much air can be pushed or pulled through the a/c at no more air velocity than 1500 ft/sec or less. If it goes more, the water is either sucked or blown off the coil. Here is a method I've found that helps.

When you jump in the truck, all the windows down, start a/c on high in full recirc. Take off to wherever, and let the wind through the truck remove most of the hot air down to ambient--5 minutes driving. Roll up the windows. Let the temp start dropping. When it gets to just above the "comfort zone", turn the fan speed down one notch. This slows the air across the coil allowing for more contact time through the fins, which will make the exiting air colder, and remove more humidity. As the cab continues to cool, drop the fan speed down another notch, chilling the air even more, and removing addtional amounts of humidity. Moisture is the silent enemy of a/c. Most of the cooling load is in moisture removal initially. As the moisture drops, the sensible temp (what we feel), will start dropping faster.

I know this doesn't get the real problem get taken care of, which is a nominally sized system, but it will help deal with the problem we all now have.

 

Ask and you shall recieve..... http://www.familycar.com/Classroom/ac1.htm This is a great site about cars in general...They cover all makes and models...As for your a/c buddy i would question him working on my vehicle if he said the condensor would drop the temp by one degree..it displaces the heat removed from the passenger compartment, as well as the heat generated by the compressor and the liguid refrigent changing into its gaseous state....if you read the above link the ideal temp at the evaporator is 32 degrees...The reason for this, water freezes at temps below 32 degrees.. so all the moisture it removed would freeze and reduce the cooling effiencty of the system. Combine that with out side air temp, system effiencity, air duct interior temp..the vents should be blowing at least 42 degrees of ice cold air out after the car has been up and running with the a/c on either recirculate or outside air. And the reason for recirculate is for extremly humid enviroments, were i live, or hot areas like the desert. the biggest misconception about a/c is that it cools the air. No, the a/c system removes moisture from the air. Thats the diffrence from being on the gulf coast with it being 95 degrees and 92 percent humidity and being in 125 degree 52 percent humidity death valley heat....it would feel the same! Only one is a lot more sticky hot. No one ever ask why a heater core burst out in your vehicle. Its the oposite of the cars a/c system. Execpt it adds moisture to the air warming it up! i know I know, thats impossible you say. Wrong. When 30 degree air is pulled thru a heater core with 170 degree engined warmed collant flowing thru it a mini storm occours, it littery rains in the core! this small mist it instantly warmed to over 150 degrees most of it evaporates, and most of it gets picked up inthe air stream and blown out the vents..ever wonder why you turn on the heat it smells like water? Thats why. And most of it settles to the bottom of the air box and starts to rust out the heaster core from the outside in. I once worked on a 1952 Dodge pickup that i guy had brought while he was in central america and had it shipped back to the states. It was mostly orignial and rust free...that made it real rare considering it was from panama..well he wanted the heater core replaced as he was going to be driving it as his work/play toy...i took the heater core out and it had no rust what so ever on it and was still stamped with the Dodge part number and stamped 8-52....The reason for this is that it was never used much if rarely, were talking 90 plus temps year round down there, not much need for a heater..so it was in as good a shape as a new one..brass works very well! Most of the newer aluminum heater cores are good for about 10 to 15 years tops. The under dash a/c was another story, i didn't have to take it apart, cause it fell apart after one bolt was removed!

 

The one thing I can think of that might help these work a little better, is a higher volume condenser fan to help reject the heat from the system better, or faster. Especially in stop and go traffic

 

Manatlarge, some good info there, thanks.

What I meant by dropping 20 degrees across the coil is that the incoming air temp will be lowered by around 20 degrees by the coil and come out that much colder.

That was also good info on the sizing of the whole unit by gonefishin.