ac clicking sound ( no cold air)

[nick1370]

ac clutch engages every 5 to 10 sec and give same clicking sound ac is charged and it is in green.....i did check the hoses and find that one just below dash board (in engine compartment)smaller one is cold and bigger one is hot and i think the small one is returning hose.why i don't heave cold air dos the big(aluminum) hose supply cold air or small one please help....ths and have nice dayP.S.on ford windstar 2000

[12Ounce]

The ONLY gauge reading that "counts" ....is the lowest one that occurs just as the clutch is disengaging. Is that reading in the green? Probably not. I suspect you still need to add refrigerant ... but don't add if the lowest reading is in the green range.

[mark_gober]

Nick,

Let me ask you a question. What type of gauge are you using? I've seen (and unfortunately, used) some of these freon cans that have the built in gauge, and my opinion is that they are crap. You can pull the trigger to get a reading, immediately pull the trigger and get another reading. I MUCH prefer a manifold gauge set. You can put them on the car and read a constant pressure so you can see what the system is doing while the compressor is cycling on/off/on/off. I'm not sure if they have Autozones where you live, but they'll loan you a set of manifold gauges for free. (you just have to pay a deposit, which you'll get back). I believe Pep Boys now does tool loans as well. Repost if you are unsure of how to use these and I'll explain.

I agree with 12ounce that I think you are low on refrigerant. The on/off/on/off cycle is almost always low refrigerant. (Could be high refrigerant too, but unless you've put some in, I really doubt it).

Mark

[tomj76]

The others are right. Frequent cycling of the A/C clutch is usually an indication that the charge is low.

Ford A/C works on the basis of two switches (contained in the same assembly). The first switch detects when the pressure is high enough to allow the pump to run. The second switch detects when the pressure is falls too far while the pump is running.

If the A/C pump ran all the time, then on cool days the temperature would keep dropping, condensation on the low pressure lines would freeze, the evaporator passages would freeze shut, and there would be no cooling from the system.

To manage this, when the low pressure lines drop below a certain pressure (which cooresponds to the pressure at which the liquid state of the refrigerant is a few degrees below freezing) the compressor clutch disengages to allow the pressure to build back up. When it crosses the cut-in threshold the pump restarts to drive the low pressure back down.

When the refrigerant is low, the pressure drops right away, the system cycles fast (10 secs or so), and there is very little cooling (because the heat capacity of the small amount of coolant in the system is so small)

In my opinion, the only information provided by the low pressure gauge is that the pressure switch is working right. For charging, you have to make sure the cycling frequency is right, and the low pressure temperature AFTER the evaporator is low enough.

Also, if you're adding refrigerant, then you're losing refrigerant. Some of the oil escapes with the refrigerant, so you need to add a couple of ounzes of oil to replace it. Also, add refrigerant with flourescent dye so that you can find the leak at a later time.