Home > Open Discussions > Domestics > a/c blows hot

a/c blows hot

  1. Please fill out the following to ask a question.

    MAKE: Ford
    MILES: 270,000 km
    ENGINE: 6.0
    DESCRIBE ISSUE....a/c only blows hot
  2. pressures are good, compressor kicks in but only for a short time
  3. Please post those Good Pressures. Also, where are you, please, and what's the outdoor temperature?
  4. Well, I had a car in my bay the other day with just enough R134 to kick the compressor. I took out 3.75oz. SO I put the nitrogen to the the system, it held 160pnds for a 1/2hr. SO I went and saw the client, told him I would inject dye after seeing if the system held a good vacuum, charge to spec, and have him come back next week to see where the leak was coming from. Must not have been a huge leak as it held for a good half hour. Anyway, what I am trying to say is, pressures may seem ok, but an undercharged system can lead to misinterpretation. After talking to the client, he stated the car had not run for two years, before that it was not a daily driver.

    My suspicion, r134 is a gas. It will seep out over time. Kind of like a tire. So in his case, I am not suspecting a huge leak. Probably none at all seeing the nitro held for so long and it held a good vacuum for 30mins also.

    So, in essence, I am not a AC specialist, but the first thing I always do, way before hooking up my gauges is exactly as you did. Is compressor kicking in. Yours is, so that means basic circuitry is fine but hot air. If the compressor is kicking and you are only getting hot air. Suspect a low charge. 99% of no cooling events when system is working is a low charge or a temp blend door actuator which is quite frequent on these trucks.

    My advice, take it to a shop where they can recuperate what is in the system. That way, if you still have some good r134 in there, you won't have to pay for a full recharge.
  5. Are you sure about this? If you are adamant about saying pressures are good, I side with JD. If the compressor is cycling but only for a short time, that is VERY indicative of a low charge.

    So here is a PDF of how to properly check your truck with pressure gauges. Make sure your low side is working as described. If you still have "normal" pressures on high and low, and compressor is cycling for a short time, I am stumped, and my suspicion of low charge is out the window. So read the PDF ace1 carefully and report back.
  6. That is one EXCELLENT test procedure!!! You'd have to pay for that, anywhere but here!

    We don't know your experience level, so we have to say things that sound elementary till we can tell what you understand about auto A/C.

    First, nickb2 mentioned a system with less than 4-ounces R134A in it. With the characteristics refrigerants have, that 4-ounces would give you a "normal static pressure." By that, I mean that if you check the system when it's NOT running, you'll find a pressure in PSI that's pretty close to ambient temperature in Degrees-F. BUT!!! a fully charged system, with say Ten Times that much R134A Will Also show that same Static Pressure. It is only till you connect an Auto A/C Gauge Set and RUN the system that you'll start getting decent diagnostic information.

    Next, be sure the Valves on your Gauge Set are turned OFF for your testing. I was helping a neighbor who knows what he's doing with A/C but was stumped by weird readings. He'd forgotten to close the valves.
  7. Yeah, the best charts that show the range of high and low relative to ambient that I have seen.

    JackC... be sure to peek at them. I'm assuming those charts are generic for R134a, not limited to this Ford
  8. @Bill, while it did come from ford and was specific to the op's truck, you will find that these readings and tests are very generic and apply to all vehicles as rule of thumb. The only thing really that changes here are that this truck has HVAC options that are different from other small auto's such as auto climate controls and such. But now days, pretty much every is out the windows on that one. Everything is auto everything. But a gas is a gas. Not much can change the laws of physics, no matter how hard one may wish it to be different.

    All manufactures always start with the same diagnosis setup. AC full cool, fresh air selected (not recirc), blower high, windows down, rear hatch or door open etc, yadayada.
  9. I just mention that ford trucks have been plagued with faulty temp blend doors. So if op finds to have a full charge system, and comp is cycling, that would be a first for me. So essentially, just by going what the op wrote, I don't think it is a blend door issue, but should not be overlooked being this is a ford truck with devastatingly poor actuators for HVAC systems.
  10. @billr , yes I did look at those charts. My A/C is working just fine, thank you.
  11. gfbidd, you are a man of few words. Hard to be helpful without more information. If if if. Pressures are good, compressor kicks off after a short time (what is short? 10 seconds? 30 seconds? two minutes?) Does it come back on again? Soon? How soon?

    Making up my own scenario here.....Ambient pressure good at about 90 psi. Start it up, pressures look good at about 35 psi low side and 200 psi (idle speed). Compressor clutch is engaged, but "kicks off" after "a short time". For my scenario, "short" will be about two minutes. Just going to add that AC suction line (the fatter one) was ice cold until the compressor kicked off. Compressor kicked off to prevent evaporator from freezing, because no air is blowing through it to keep it from getting too cold. No air reaches it because blend door is stuck at "hot" position due to failed actuator. But I'm just guessin".
  13. thanx, I will do this test and report back
  14. ran the test, lowside 70-75psi and high side 125-150psi-with valves closed! clutch kicks in for about 30 seconds at a time, outside temp around 25 celcius So does this indicate an issue with the orifice tube?
  15. 25 Celcius is 77F. If the orifice tube is no longer doing it's job of providing a preset restriction to refrigerant flow, then it might be the reason for those pressures. I will use the phrase "blown open" to describe that type of failure. I can't remember ever seeing that happen. "Plugged up" is what usually happens.
    If no problem is found with the orifice tube, the other likely problem would be a worn out compressor.
  16. The numbers look to me like a compressor issue - nothing easy inexpensive..
  17. Were those pressures taken while the compressor is cycling or off?
  18. Thank you, I will check out the tube, if I can find it!!
  19. Pressures were read while not cycling, were both higher when the compressor was on.
  20. Thank you, so where exactly is the orifice tube?
  22. Well! That's pretty simple! Thanx
  23. Hey! Finally got it all fixed!! Yes the orifice tube was plugged, very much so, the cause was a failed compressor!! Replaced compressor, evaporator orifice tube and drier, also flushed the rest out with brake clean and let dry. After a good evac and recharge all is good! Thanx a lot for everyones help!!
  24. Thanks for letting us know the outcome. We're always glad to know. Sorry it was labor intensive and parts expensive, still glad it's working now!