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2019 Jeep Grand Cherokee AC issue.

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  • 2019 Jeep Grand Cherokee AC issue.

    Anytime I lightly accelerate, the compressor will cycle off. If I let my foot off the gas or push the gas pedal down further the compressor will cycle back on. Evaporator temp is generally around 39-41, and when it cycles off it can go as high as 55. I know that cars are designed to cycle the compressor during wide open throttle, but barely pushing the gas pedal it shouldn't be cycling off? Seems to do it mostly between 1500 to 2500 RPMs. Any advice appreciated!!!

  • #2
    OK, yes assorted cars/trucks shut off compressor WOT or high load idea is give you the power.

    What happens if you leave a thermo in dash vent (center) when this happens to outputs?

    It may have a code in wait if it drops holding reasonable temps. That is near certainly a combo MAP (manifold vacuum) converted to electrical info for computer engine controls.

    A/C - if wrong other things are wrong it will not run properly or change.

    Hard to monitor while driving but fan(s) may shut off if incoming air is adequate by itself.

    So see if they work at all may be just one Jeeps have assorted options might be two?

    Last - surprised you hear it from inside cabin?
    MetroWest, Boston


    • #3
      I can tell it shuts off when I accelerate barely pushing the pedal down. I use an OBD sensor that shows when the compressor is on/off, evaporator temp, and target evaporator temp. When lightly accelerating the evaporator temp will go from 39-41 to as high as 58 and I get warm muggy air blown in my face. If the compressor cycles off and I let off the gas OR push down on the gas pedal to the point it downshifts the compressor comes back on, so not sure how this would help give more horsepower, it just doesn't make sense. I've only known vehicles with fixed displacement compressors to disengage when flooring it, not revving 2-2500 RPMs.


      • #4
        If it is speed related, I would think the pressures are out of wack. From what I can see the whole ball of wax is controlled by the electronics, not pressure switches. There is a pressure transducer in the refrigerant line that monitors pressure. You are going to need someone that knows the system.
        What has been done to the system recently? Could be over or under charged, could have some restriction. Pressure readings would help, esp when it cuts out. Any codes being set? Nothing is simple anymore.


        • #5
          Let's get this fixed if we can. IDK what "thing" you have to watch through OBD port these and others are so teched out to meet emissions and max out MPG one item off the others get wrong signals - Domino effect goes brain dead.
          YOUR device if it wasn't well over about $4,000 bucks isn't trustworthy IMO to watch as the car does if that's right.

          I default with humid air noted it's probably icing evap then quick melt upon compressor off all but visible fog out vents - sometimes have seen that for real!

          If nothing else systems crude basics are a proper charge by known weight so suggest it evacuated and recharged still only way to know. That machine cost more than the shops like to pay guess, $20,000?

          Oh yes and a monthly fee so it keeps working and record what it did. "Beam me up Scotty!"

          System holds so little refrigerant 1-2 ounces off forget it - many now and this one.

          Fans, compressor on or off, RPM air temp in, engine temp, load on engine, which gear it's in all at the same time and engine run well.

          So I have to suggest live data by credible equipment or DIY a plain vac and charge to known weight make a basepoint to even know if there's a problem which still the common problem is low charge from a leak.

          As Cornbinder asked what has been done already if you know? Lots of problems are caused by failed attempts! Current EPA hoses, gauge end hook ups don't even flow to spit clear out air A FAILED law you touch it you also added air now the problem?

          Known basepoint or no way to proceed,

          MetroWest, Boston


          • #6
            I have also measured the air coming from the vents and it seems to be inline with what I see on OBD JScan. The system was checked twice by the dealer and they said the charge and pressures are fine and it is "operating as designed". I don't believe the evaporator is freezing over. The thing is, if the compressor is running, it will stay on until it reaches the target temp then cuts off. So while I'm driving and accelerating lightly when the temperature of the evaporator rises above the target rate, it calls for the clutch to cycle on then it will start to blow warm air until I either let off the gas for a split second, or if I accelerate harder then it cycles back on. When I'm stopped at a light, or driving a steady speed, the system works absolutely fine either on city roads or going 75 on the freeway. I'm thinking it is designed this way for the vehicle to save 0.001 miles per gallon? The system meets and keeps the target temp as long as I'm not lightly accelerating. If it were a pressure issue I would think this problem would occur constantly, especially if the vehicle isn't moving and head pressures go up. Hmmmm.


            • #7
              Originally posted by chaosthyre
              I have also measured the air coming from the vents and it seems to be inline with what I see on OBD JScan. If it were a pressure issue I would think this problem would occur constantly, especially if the vehicle isn't moving and head pressures go up. Hmmmm.
              You are assuming there is a single set-point, but with electronics and transducers there is just a varying input, and based on that, outputs are determined. Just as there is no set switch that turns on the CEL, there can be no set pressure that causes the system to turn off the compressor.


              • #8
                It's playing hide-n-seek IMO. How many miles on this?

                Basics: A/C is a load to dance with while saving that .001 MPG mentioned. Keep saving finally it adds up kind of leave nothing out.

                Behavior is backwards to me as it works accelerating and cuts out when I think it should come back on.

                Miles do things like wear out or dirty intake tiny ports that if so altered real or sensed pressure after throttle plate(s) to achieve mixing fuel and air split second controlled so what can be shut out. Temp monitored everywhere (by the vehicle) changes split seconds too all this so it drives well, stays in control A/C just a pest/load tossed in.

                Need real observations if/when sensor is wrong the others will make wrong readings so check for real not the scanner's report on these temps things with miles unmetered air gets in all may still run well but is off.

                It has to burn off fuel vapor ever fumes more or less dump that at engine when it can handle it - a wild algorithm of calculations in split seconds.

                Ground up A/C last and staying in perimeters of where it can run properly first.

                In short - it needs to run well, no air leaks or dirty sensors first known right the rest relies on that.
                a 2019 soon could be 5 full years old (100k?) has had time to have miles and exposure for the concert of sensors to fail but not show.

                Super high end scanners may find one or just look at overall situation A/C needs a proper running engine as everything else or not point to it being a vehicle at all. Follow me?
                MetroWest, Boston


                • #9
                  It was built May 2019, it has 42K on it. My next vehicle will have a variable displacement compressor, I don't seem to notice temperature swings like I do with my Grand Cherokee.


                  • #10
                    IDK how long you like to keep a vehicle that's new for me. Just variable may not change it rather controls inside couldn't say next year's options,

                    Just chat and personal - I own similar to this set up does vary holds just 13oz charge, works, all temps on target does vary outputs watched live all vehicles 3 I use.

                    Ones over the ages was games with climate controlled ones with range of temps really stink! Cool to scare you but 3/4th my year is heat want to defeat it when/if covered in ice then snow impossible to clear off all windows it's happy inside max 85 vs perhaps a windy 5F just carry spray windshield washer fluid. If your scene don't warm that up it will bust windows.

                    The best of best is now antique GM's 60's into some 70's climate controls concentrated on whole interior Cadilac - Buick best land yachts power vented out rear (some) or channel heat thru floors!

                    All had vent window, some in rear control inside with them to suit others just noisy on highways.

                    Worst two features even and still are auto-dimming headlights (current no choice but off) and cruise control really special when wheels are like in air on ice (could bump some would be on by mistake) now just don't use that at all.

                    Light dimming with snow banks are a crossroad is special - high low like some seizure if a home there OMG how annoying.

                    Current Jeep the unwanted interior light delay so nice never the same no matter what of course stand in rain waiting for them to go out for sure.

                    Dammit I closed the door that it - laugh.

                    All the best performers A/C had the A-6 compressor and TXV set ups. Held several pounds of R-12 cool off car sitting in sun in no time still!

                    Ones I kept of 100s personal use or flip cars still rusted out if used here in Winter - nothing really solves that except don't use rock salts I think 4 snow states don't vehicles and the roads/bridges last ages longer but folks can't drive so use lots of it here so said 70% of bridges/overpasses are actually at the unsafe mark now is shocking,
                    MetroWest, Boston