It should have one, call your dealer and ask about it. But in the mean time the condensor core, sits in front of your radiator, clean it. Also make sure your not low on coolant. an easy check for the heater core is to feel the hoses, if one inlet is hot and the outlet isnt so hot your core is clogged

 

The evaporator drain i should have explained more to, heat is attracted to cold, not the other way around, thats why your cold glass of beer ends up sweating, the humid hot air around the cool glass penetrates into the glass warming the beer up, the water is from the humidity. This is the same on your evaporator core. The heater core keeps these from freezing and the air running across the coils pushes the condensation off the coils and collects into a drip pan if you wanna call it that. The drip pan has 1 maybe 2 drains on it connected to either a hose or free standing nipples. If these drains are clogged, the water will accumulate into a puddle, the puddle starts freezing and eventually it ices stuff like your flaps up. This is one of those overlooked problems we sometimes find on the busses as well.

 

Okay. Fuses are good, havent checked the switch. Still no luck on finding cabin air filter. Both heater core hoses are hot, coolant is at the full line, and the drains are unclogged. When truck cools down I will clean the core and other coolers and radiator when truck cools down. Bugs and junk stuck in there.

 

I had the mech. at work check freon this afternoon. It was low, by 3 cans. The problem was intermittent so it will be a week or so to see if that was the problem. The air out of the vents at idle is 31 degrees. Is that normal?

 

I think you've found your problem(low freon). Now you have to find the leak.

Where you at in La. ?

 

Ive got a good idea that it is leaking to lose that much freon. I live in Houma.

 

go to autozone and get an electronic nose that sniffs for freon, better than the dye kits

 

If a tech says that you were three cans low on R134a I would not be too happy with the tech. Real A/C techs do not use 12 oz cans but will use a dedicated A/C Service center that recovers all the R134a from the system and displays the weight of the refrigerant that was recovered. Comparing the recovered amount in relation to the specification will give you an idea as to how much has leaked out over time (% of leak). The number one source of leakage in an A/C system is the service ports, 20%. The best why to check the function of an A/C system in relation to the underhood componets is temperture. The difference in inlet and outlet at the condenser should be between 25-35 degrees. The increase in temperture at the condenser should be 0-5 degrees. The difference in air temperture at the center vent and the outside air temperture with the doors open and the truck in the sun should be 30-40 degrees.

There is no cabin filter for the 3rd gen Dodge Truck.

Use something that desolves bugs to soak your heat exchangers while they are at full temp. Then wash with low pressure water from the back side to backflush the heat exchangers.

Check a factory shop manual to see if there is a vacuumn check valve under the dash for any of the air control doors. If there is a vacuumn leak somewhere you will see that the functions will be closest to normal at idle or steady cruise light throttle (high Vacuumn). If you go to WOT than the vacuumn decreases and the functions of the Air Control devices will change.

Low refrigerant level requiring three 12 oz cans is almost the whole system capacity so your techs answer is lame. The system would not blow normal for 50 miles and then start acting up with just low level. 10-15% low would give you ok temp while traveling with good air flow through the condenser and poor temp when at a stop light with poor air flow.

Icing of the Evap is possible if running in fresh air mode instead of recir mode on a humid day. Run in recir position and once the humidity drops inside the truck it can't ice up any more. Add a little temp with the A/C on will also keep the evap from icing. The icing will be an intermit type of thing but being in recir will greatly reduce or prevent this.

A/C is the second hardest thing to fix on a car correctly the first time. Auto Trans overhaul is number one.

Good luck!

 

I stated once before that low freon will NOT cause an intermitten problem. You simply can not have cold air for 45 minutes then lose it like that. Is this problem still happening?
The last guy brings a valid point with the recirc. I never turn my heat control from recirc ever unless im using the defrost. This sounds more like an icing problem or an air circulation problem over the condensor core. I have not a clue about cars but busses have pressure switches, low pressure and high pressure. If the pressure goes to high the compressor shuts down, same with low pressure. Is this a feature on vehicles now? this problem sounds more like a dirty core that needs to be cleaned more than anything. But this is based purely on the 2 ton systems I work with.

 

"Icing of the Evap is possible if running in fresh air mode instead of recir mode on a humid day."

This I believe is wrong, Even though you are running in recirculation mode you will still get humid air entering the evap core. D.O.T regulations on any commercial or private vehicle says 10% has to be fresh air. When recirc is on the fresh air vent does not close all the way, It just restricts how much outside air hits the interior of the vehicle. This could still allow a freeze up.