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A/C cools only at high RPM

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  • #1

    A/C cools only at high RPM

    1992 Auto

    Old compressor locked up, salvage yard compressor has the same symptoms as the original.

    RPM's must be 2000 and up for the system to blow cold air out of the vents. When working it is dropping almost 40 degrees below ambient temp. Condenser fan is not working (maybe related to the problem, but I don't think it is the cause). Tried an electric fan and even a leaf blower at idle, will not blow cool even though compressor is turning. At 70 mph at idle, will not blow cool.

    Maybe a pressure switch? Thanks
    Tags: None
  • #2
    No cooling fan function will cause the air to warm up, then something will give.

    Air in the system, higher pressures from over fill, too much oil or dye all can cause your symptoms and no fan will make you pull your hair lol.
    134 will also be warmer but not by much. Some of the drop in replacements actually work better than R12 but if you cut an AC hose with a torch
    it is possible that it could ignite the leak with the torch. Don't quote me but I believe the worst of these as far as petro content have to have temperatures at 1100 F to sustain ignition. Excluding those using propane.

    Fix the fan, if performance is poor evacuate at maximum vacuum for 20 minutes then charge with refrigerant. Make sure the transition from vacuum to filling or charging does not allow any air in anywhere.
    Last edited by Movin; 09-05-2015, 03:31 PM.
    Reflex paint by Langeman...Lifted...Tow Rig

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    • #3
      Refilled with Enviro-Safe. They actually recommend to not vacuum down before charging the system. Maybe to prevent overcharge, not sure why really. Installed new fan, but still inop. It's been a year so I cant recall exactly, but I do have power to the fan, which confuses me also. A/C works great on a trip, but not so good around town at stop lights.

      Actually was hoping you'd see this post. I think you are my best chance to get this issue fixed. I am far from a mechanic, and even worse with A/C
      Last edited by Skrapbob; 09-05-2015, 03:41 PM.

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      • #4
        Lots of us know the fan circuit. The relay and temperature switch actually ground the negative side of the motor to turn it on. The default position is on all the time. You may have a missing relay, burned out relay or small ground wire to body unhooked around the battery.
        Reflex paint by Langeman...Lifted...Tow Rig

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        • #5
          First how are you going 70 at idle in Kansas. Ive been to that state, Its flat.

          Do you have access to gauges? Id like to know your pressures before i comment.
          Lil' Red Rocket '93 Festiva: Stock, A/C, Rear wiper, Rear defrost, Alloys, Power mirrors, White Tach,Super tail action (factory spoiler)

          Frogstiva '92 Festiva: Just bought a HOT MESS. BP swap with E trans (not done), Built Red from factory spray bombed black with stripes, Aspire swap, Escort GT Master Cylinder, found frogs in vehicle, hence Frogstiva, pulling all good parts for Lil' Red Rocket.

          1.7 PN Diesel and trans, waiting for good shell.

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          • #6
            Could have a bad expansion valve. You should check High and Low side pressures with gauges although a bad expansion valve would probably keep it from cooling at all. Slow leak maybe? Debris in Accumulator?

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            • #7
              Hmm I did envirosafe as well with no vacuum as it said on the can, and it only works at high rpms and when going above 45mph, and it's not freeze you out cold in the slightest. Works like a treat when there is no sun out. I think the complete lack of tint really really hurts the a/c performance in these cars. Also not having a condenser fan doesn't help much.

              I didn't change my expansion valve when I installed the system, only because I was bending pipes trying to remove the dang thing.

              I was thinking of just putting a vacuum on the system anyway and try it like that. That or I could just pull the whole system and sell it, and do a BP swap. Lol

              Sent from my LG-D800 using Tapatalk
              Last edited by TorqueEffect; 09-05-2015, 11:57 PM.
              1991 Ford Festiva BP (Full Aspire/Rio Swap) (337k Miles) (Around 95k Engine)
              2002 Chevy Cavalier LS Sport 2.2L DOHC Ecotec (Threw a Rod)
              1998 Chevy Monte Carlo LS 3.1 V6 (225k miles) Best MPG = 28

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              • #8
                BP swap would definitely make the car cooler!

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                • #9
                  The system would not even charge at all without bringing the revs way up. Is it possible for the system to be overcharged right away?

                  Originally posted by seniorgreenpants View Post
                  First how are you going 70 at idle in Kansas. Ive been to that state, Its flat.

                  Do you have access to gauges? Id like to know your pressures before i comment.
                  It doesn't stay at 70 for very long lol. Just trying to say that ram air does not help it cool (ie: condenser fan). The rpm's must be high.

                  I will have to try to borrow gauges again.

                  Originally posted by Movin View Post
                  Lots of us know the fan circuit. The relay and temperature switch actually ground the negative side of the motor to turn it on. The default position is on all the time. You may have a missing relay, burned out relay or small ground wire to body unhooked around the battery.
                  The fan circuit is defeating me so far, but this is good info to know.


                  Originally posted by zoe60 View Post
                  Could have a bad expansion valve. You should check High and Low side pressures with gauges although a bad expansion valve would probably keep it from cooling at all. Slow leak maybe? Debris in Accumulator?
                  This has me curious

                  Originally posted by zoe60 View Post
                  BP swap would definitely make the car cooler!
                  Bp with A/C would be even cooler!


                  Thanks for all of the great input! This forum is the reason I still have the Festiva.

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                  • #10
                    sounds like the compressor isn't working as good as it should. Like enough at high rpms but not at low. Mine has a crappy clutch on it and sticks a little when I turn it off but makes a noise and drives me nuts going to pull a compressor and see if I can swap the clutches.
                    88 Ford Festiva LX "Miogi" B8-ME swapped.

                    93 Ford Festiva L "Haywire" Rat infested trashcan WIP

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                    • #11
                      Probably got a little air in it, you may have to vacuum anyway to get the air out. Be certain no air gets in when you make the transition from vacuum to filling the system.
                      Reflex paint by Langeman...Lifted...Tow Rig

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                      • #12
                        Gonna try a recharge with vacuum. I think enviro-safe was ordered to pay a fine and stop production

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