2007 ford taurus (out of warranty, 42k)
hi - I can’t get any cool air out of this unit. I turned the aircon on to MAX and checked the low-side pressure. It cycles continually between 25 and 45. It goes up to 45, the compressor kicks in and the pressure goes down to 25, the compressor stops and then the pressure goes back up to 45. Then it repeats. The cycle is 12s-15s.
I don’t know much about aircon, but thought that maybe I needed a charge. Seems like something else is wrong. I would appreciate some clues. Even if I can’t do it myself, I’d like to understand it.
thx,
rob
That cycle period is much to short,should be more like 3 min. You do have a charge problem and you do have a leak.
Thanks for your reply. Should the pressure be constant? Do you think that there is any hope by using a sealer and recharging? Also, is it possible that something just needs to be tightened to fix the leak?
thx
The pressures are never constant both move with the low moving much faster and more often than the high (but you cycling is a good indication of a low charge)
No sealer is to be used under any circumstance. See if you can aquire a electronic leak sniffer. I don’t have any pratical experience with your model. Likely places are the service ports,compressor shaft seal,drier fittings,condensor, expansion valve (if FORD is using a drier reciever system) and the evaporator,not likely something loose.
Can you see a dusr covered oil trail any where? this is the visible sign of a leak.
With the A/C on for a few minutes and the engine idling raise the hood and careully place your hand on the tube from the firewall into the accumulator (a large canister arrangement) and note if it’s cold to the touch.
It should be cold and likely sweating due to condensation.
The pressures sound about right to me.
If it is cold and sweating then it could be that the car has a blend door problem.
I’m not that familiar with the arrangment on this particular model but I believe it uses a stepper motor (common on many late model cars) to operate the door.
(The blend door is what shuts off the heater core and prevents hot air from being blown through the vents.)
As to whether it’s a stepper motor or mode control (dashboard selector) issue I do not know.
I agree the low side pressures are OK but the cycle time is so short.
phew - I’m glad that both of you agree about the pressures 
That was confusing to me!
I will look into what you suggested. It seems like a great starting point.
Do you think if the blend door isn’t working properly and not sealing out the hot air, that might explain the short cycle times; the compressor trying to keep up but never cooling? (I don’t understand how sensors relate to the whole setup, but I’m taking a guess…, I’m going to read an aircon tutorial tonight)
thx,
rob
This probably had dye in the system from the factory. Do a careful inspection and see if you can find the leak that way.
It’s fixed, at least temporarily. I added refrigerant and it stabilized the pressure and the cold air came on! Cool! If it lasts a year or so, that’s not too bad. We’ll see…
thx for the suggestions