Hmm, I'm not sure I'm to be honored and feel respected, needed and appreciated.......or.......feeling used, placated and being setup.
Oh well, I guess I'll be a willing go to gopher.
I think at least I won't loose too much on this deal,.....like a pcm!?!
I will settle two issues here, one electrical and the other refrigerant. Firstly, on the matter of two, four or six wires going to the compressor, the answer is, there are six wires going to the compressor vacinity. They all originate from the same wire loom, bundle that goes between the alternator and ps pump and joins the alt. wiring. As Rod and I both expected, there are ONLY TWO wires that directly connect to the ac compressor. They connect to the top of the clutch field, which is right behind the serpentine belt pulley. And if anyone is wondering, the 3.0 and the 3.8 engines have the same ac compressor, accumulator and sensors arrangements. I know this because I just looked at them both in the "sheet metal." And, the compressor is the lowest, frontmost accessory on the serpentine belt under the power steering pump.
Now, on to the remaining four wires. They connect to the hi pressure/hi fan relay switch, which I figured was the cause of the confusion all along, as this switch is located behind the compressor, screwed into the hi pressure line coming out of the back of the compressor. It has a square four wire connector to it. As all of this is squashed together and interconnected behind the compressor, it could appear that the compressor is the recipient of the 4 wire harness, instead.
Now for the second issue at hand, also putting myself, my vehicles and my wallet at peril,
, I will address issues of ac refrigerant pressures. In order to get the ac comp clutch to engage, the
MIN. pressure as measured at the low side ac clutch cycling switch is
45psi, which typically should be very close to the low pressure side gauge and charge port. As it turns out, when the ac isn't on, nothing is heating or cooling it and the refrigerant pressure inside the ac has equalized throughout it, us technical folks like to say, the system is currently static and the conditions are steady state. It's just a fancy, though concise way to say that you can measure the pressure and other information anywhere in the system and get the same results. So, for example, if you measure 45 psi at the low pressure port,it will the same at the high pressure port. So in short,
at anytime, if you have less than 45 psi at the low port, it won't come on.
Now, on to filling the system enough. These systems have a known volume, which the smart folks at Ford optimized the right amount of refrigerant to use in the system, so all an ac tech needs to do is to put the right weight of refrigerant in it, which often is on the underhood decal. Typically, these systems take two to three pounds. A measuring container that converts weight to volume can be used instead of a weight scale to put the right in. Anyway, without the proper equipment, most of can't do it right or well. But, as a rule of thumb, I have determined that these systems have enough refrigerant when they have
65 PSI at 55 to 60 deg F with the ac system in a static, steady state condition. (most conveniently measured at the low pressure port) So, below 65 psi, you most likely don't have enough in it.
So, as said before, the ac will kick on at 45 psi or higher. Only the high pressure switch will turn the compressor clutch off when the system pressure is too high at 430 psi, which is rediculously high! It will return closed at 250 psi allowing it to run. The hi fan switch will switch on the fan to hi at 325 psi and off at 275 psi, returning the fan to the normal low speed setting, which is turned on by the pcm.
AC systems are counterintuitive, so what I'm going to say next doesn't make much sense, but as said before, when the pressure is 45 psi or higher, the compressor comes on. BUT, when the low side pressure GOES DOWN to
25 psi, it kicks off. Then the pressure will start to rise till it hits 45 psi again, the compressor comes on, then off at 25 psi. So, say you have 44 psi when you start your car cold. The ac won't come on. Then, if it gets hot enough to get the 44 psi to 45 psi, or you add more refrigerant to increase the pressure, the comp will come on, Then it will real quickly compress the rfrg (or just screw, I guess that would depend on the compressor, nah, screw comp will still compress, screwy
, sorry, that's from a brake discussion here) to 25 psi and then cutoff. But, because there is not enough rfrg to do much cooling (or more correctly, technically speaking, remove heat), it will immediately return to 45 psi, kick on the comp and so on. This is known as short cycling. Another words, if it short cycles, it needs more refrigerant.
Whew! I hope that covers it. I need a nap! Good Night!
