2001 ranger 2.3 liter

truck blows good and cold then it starts to smell damp and then it slowly stops blowing even though you can hear the fan running. if you turn it off and wait a while it will start working again. drier drips good evaporator enterance and exits seem good if not frozen. great pressure differentials. but no water is dripping out of evaporator case. I pulled the fan and the evaporator was driy not damp at all. Great pressure drop at 70 degrees ambient 24 psi over 150 psi I am getting 32 degree vent temps on mac ac with windows closed.

I am guessing its the thing that cycles the ac to keep the evaporator from iceing up. Is that the little thing with electrical looking coils in the evaporator case that you can see when you pull the fan out? (that's the blower motor resistor I am describing does it turn the ac on and off to get to keep it from freezing?)

I had someone tell me it could be low refrigerant also?

 

Correct on cycling to keep evap from freezing. Never verified this on Ford (what are you driving?) but on GM's the low pressure cutout can be adjusted. 24psi suction side at 70* ambient and with no system cycling due to cutout = frozen evap core. That 24psi = less than freezing thep. If not cyclling, try to see if your low press cutout can be calibrated or just replaced. On GM, those just screw on, there is a schrader valve in there, you don't need to drain and recharge the system to remove/replace or remove/adjust the valve. I'd expect no less from Ford; someone can probably confirm.

Edit: If you do a google, you will find charts showing temp for various pressures of various refrigerants. On this, you will notice, MOL that in the 20 - 35psi range (give/take a tad) that temp approx equals pressure.

 

The LPCO switches on Ford products are adjustable, though I don't guarantee every single one sold has that capability. With the system stabilized, i.e., running for 10 minutes or so, you can remove the LPCO electrical connection, and using a flat blade screwdriver adjust the cut out pressure.
If you have evaporator freeze up occurring, you are cooling the evaporator below 32F enough that the condensate is freezing, which occurs when the refrigerant boils at a low pressure. Increase the minimum pressure, and the refrigerant won't boil until it gets a bit higher in its temperature range.
If the system is cycling while you drive down the highway in a 'high demand' mode, it's hot outside and not cool inside, then you may be low on refrigerant. In that case the LPCO is cutting out the compressor clutch power because there is no refrigerant coming in to boil, and the pressure is dropping so any that does come in will boil at a low temp. In that condition, the compressor is being starved of refrigerant and the lube that keeps it together. The oil mixes with the refrigerant like gas/oil for a two-stroke, and the oil is carried into the compressor that-a-way.
Check the cut out pressure, and adjust if needed. If the cut out is at the correct pressure(==temperature by default) you may be low on refrigerant and should have the system checked for leaks, evacuated, and recharged with the proper amount of refrigerant.
tom

 

Restricted airflow?

 

wow great info, I will try to see if it has an adjustment.

when you turn the engine off you can hear the refrigerant boiling around the evaporator or dryer, I don't know which. The compressor did not cycle in the 20 or so minutes I ran it.

 

The blower motor resistor has nothing to do with cycling the AC. It simply allows you to have different blower fan speeds. The low pressure switch shouldn't let the pressure get so low that the evaporator freezes. I don't think they're adjustable either. I would just replace the switch and see if that fixes it.

 

The switches that are adjustable have an adjustment screw or slot between the blades of the terminal. If you remove the connector, you can look into the switch and see the slot.
exranger06 have you ever looked?

 

My old Crown Vic had the same problem. Turned out to be the compressor clutch RELAY stuck closed. Just a thought.

Try swapping it with another relay. It's free and will take 30 seconds.