BULLS-N-BRONCS

I recently acquired a 94 Ram p/u. During the summer the a/c would blow cold and forceful for a short period of time and then stop blowing. Now the heat is doing the same thing. No rhyme or reason as to when it will function or not. Also, the a/c lines under the hood are continually iced up. I don't believe that is normal and think it has something to do with how the whole heating/cooling system works or doesn't work. Can anybody share some knowledge about this or turn me onto a source that can help me solve this? Starting to get cold here in North Central Washington and heat would be nice. Thanks for any help anybody is willing to offer.

SIXSLUG

A/C system doesn't have anything to do with heat...I'm thinking blend door malfunction. Search Heater Treater and Blend door in this section.

BULLS-N-BRONCS

Busboy

All the air coming into the cab first passes through the evaporator core then is "blended" with hot air from the heater core. If the evaporator core freezes up the air cannot pass through a block of ice so no air flow. The AC compressor will run in all modes except off and vent so try selecting off or vent for awhile but also make sure that the evaporator condensate drain is clear. If the drain is draining the have the AC system serviced, it could just be low on freon or you may also have other problems with it. I think 94 still used an expansion valve rather than the capillary tube on later trucks. The expansion valve would be a fairly easy fix.

SIXSLUG

What Busboy says makes sense. What would keep the a/c compressor running all the time?

Busboy

Most vehicles are designed so that the air coming into the cab is dried before being heated to avoid fogging all the windows. The drying is done with the cold evaporator core and the moisture drains out through the drain leaving dry cold air that some can be directed through the heater core then mixed with the remaining air to give dry warm air. A low freon charge will cycle the compressor rapidly, a bad expansion valve might also meter the incorrect amount of freon into the evaporator both would be causes of the core freezing up. I'm pretty sure the 1994 still used and expansion valve. After a quick look on Napa the 1994 uses a fixed orifice tube unless it's been modified. An orifice tube allows a set amount of freon through an orifice inside the tube, they cannot be serviced and must be replaced if faulty. The most common cause of a fixed orifice problem is a spec of dirt that is partially blocking the orifice and not metering the correct amount of freon into the evaporator. This might come from the system being serviced or possibly the drier. First thing check the evaporator drain then see if the compressor is cycling rapidly.

torquefan

My AC did the same thing a couple years ago. The reason that the compressor cycles is to keep the evaporator from becoming too cold and freezing the moisture that is attracted to the evaporator's fins. Mine would blow ice cold for a little while, then gradually I would lose airflow and cooling. The cycling switch (mounted on the accumulator) was shorted internally and would keep the compressor running constantly instead of cycling. I replaced the cycling switch and all has been well since.

Your issue with the heat may be caused by the same issue, or may be something separate. I would look into the AC part first and go from there.

AlpineRAM

To me it sounds like he has a fan problem.. that the fan stops blowing.

If that's the case I'd look into the blower resistor and the blower motor, resistor can be ruled out if it works OK with the fan on max.

torquefan

You may be right. I was reading it like the fan's air flow reduced or stopped, but maybe the whole blower motor stops working.