AC experts step in

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    AC experts step in

    Ok, this is somewhat embarrassing because I'm somewhat of an AC expert. I maintain walkin freezers and coolers at our restaurant. Also the AC there. I have all the good quality tools and equipment for working on refrigeration stuff. I have an EPA license to buy freon. Most of my experience is not on auto, but the theory is the same.

    Im working on my 90' Bronco. It was originally R12 converted to 134A years ago. It works, but I've never really been happy with it. Recently something went through the grill and put a hole in my condenser. So I got a new condenser, dryer and orface. Blew everything out, put a good vacuum on it and refilled with new freon.

    It works, but I'm not happy with it. We have a newish Vette and the temp at the vent is 48 degrees in a matter of seconds after startup. (95 outside) It gets colder if you drive down the road. We have a beater PT Crusier that will blow 52 degrees pretty quick. My Bronco doesn't go below 60 no matter what. It does blow lots of 60 degree air and it will cool the truck after 5-10 minutes, but why so warm?

    I kind of determined to get it working better. I pointed a lazor temp at the receiver/dryer and got 52 degrees. That reciecer is after the evaporator. So why is it colder than the vent air? I pulled the evaporator and cleaned the fins. It wasn't really dirty, but I thought it might help. No joy.

    At this point, I'm thinking of replacing the evaporator. Right now everything is new except the evaporator and the compressor. The gauges show the compressor is working, so I don't really see how it could be the problem. When I google evaporator problems, all I get is leaks. Mines not leaking. Have any of you had one clogg up where it doesn't work?

    Am I missing something else?
    Check out my project
    https://irate4x4.com/general-4x4/2779-amphibious-hemtt

    #2
    fan clutch

    Comment


      #3
      there are two orifice tubes for the ford trucks one for r12 and one for 134a. Makes a world of difference in the performance on a converted system. Don't remember off the top of my head which is which though.

      Comment


        #4
        Buy r12

        Comment


          #5
          Originally posted by BJS View Post
          there are two orifice tubes for the ford trucks one for r12 and one for 134a. Makes a world of difference in the performance on a converted system. Don't remember off the top of my head which is which though.
          I was gonna say check if you have the right orfice tube installed.

          Comment


            #6
            Pinch off the heater hoses and see if the temp drops.

            Comment


              #7
              try blowing air across the condenser or running water over it. If that helps then yes fan clutch or plugged condenser.

              It is normal to lose 10 degrees between the evap and vent outlets. Maybe not normal but within spec.

              Also, is there flow through the heater core? Buy a bypass valve like used in the mid 90s cherokees, they have 4 hose barbs and completely bypass the heater core. Keep that heat out of the box.

              Another trick is to adjust the pressure cutout switch so it doesn't kick off till about 10ps, maybe 5. Helps keep the pressures down and everything lasts longer.


              Comment


                #8
                Originally posted by crisbee1 View Post
                fan clutch
                I converted to E-fans a long time ago. They helped at idle.

                Originally posted by BJS View Post
                there are two orifice tubes for the ford trucks one for r12 and one for 134a. Makes a world of difference in the performance on a converted system. Don't remember off the top of my head which is which though.
                I have the orface tube for 134A. I also tried a "variable" orface tube. Someone on another forum said they were great. Didn't notice any differnce, so I went back to the fixed tube.

                Originally posted by M92PV4U View Post
                Buy r12
                It's a thought. I would have to convert back. (Not a real big deal.) The issue is I have rode in other Broncos of the same period that would freeze you out. Why doesn't mine?

                Originally posted by Jason4x4 View Post
                Pinch off the heater hoses and see if the temp drops.
                I have a bypass valve on my heater hose.

                One thing I was wondering. I have headers. They are real close to thebox where the evaporator is. The air that goes through the evaporator immediately hits a plastic piece that turns it into the cab. It's like 6" to the headers from the plastic piece. This is stock. Has anybody covered that plastic with some kind of aluminum?

                Check out my project
                https://irate4x4.com/general-4x4/2779-amphibious-hemtt

                Comment


                  #9
                  Originally posted by Tiha View Post
                  try blowing air across the condenser or running water over it. If that helps then yes fan clutch or plugged condenser.

                  It is normal to lose 10 degrees between the evap and vent outlets. Maybe not normal but within spec.

                  Also, is there flow through the heater core? Buy a bypass valve like used in the mid 90s cherokees, they have 4 hose barbs and completely bypass the heater core. Keep that heat out of the box.

                  Another trick is to adjust the pressure cutout switch so it doesn't kick off till about 10ps, maybe 5. Helps keep the pressures down and everything lasts longer.

                  Condenser is brand new.
                  Has E-fans that work great.
                  Heater is bypassed.

                  What pressure switch are you referring to? 10 psi? The system runs over 40 psi on the low side.
                  Check out my project
                  https://irate4x4.com/general-4x4/2779-amphibious-hemtt

                  Comment


                    #10
                    Are the blend doors in their respective positions? Also isolate the heater core as stated above.

                    Comment


                      #11
                      Is this driving or sitting? Older cars do not perform as well as newer cars in traffic like conditions, I have always added an electric fan and relay just for the A/C to blow more air over the condenser when idling in traffic.

                      Comment


                        #12
                        Stupid question, did you put the proper amount of 134a in? I can't recall the formula... But it's like 85% of the r12 capacity or something.

                        Does the compressor cycle? What's your high side and low side pressures? They can tell you a lot about what going on....


                        Edit:

                        (R12 capacity X .9) - .25lbs = r134a capacity
                        Last edited by Foxmxrcer; 06-30-2020, 11:15 AM.

                        Comment


                          #13
                          Originally posted by dave_dj1 View Post
                          Are the blend doors in their respective positions? Also isolate the heater core as stated above.
                          Well, the AC works in normal and it increases in max. So I guess they work OK. Heater is bypassed.

                          Originally posted by welndmn View Post
                          Is this driving or sitting? Older cars do not perform as well as newer cars in traffic like conditions, I have always added an electric fan and relay just for the A/C to blow more air over the condenser when idling in traffic.
                          I have good working E-fans.
                          Check out my project
                          https://irate4x4.com/general-4x4/2779-amphibious-hemtt

                          Comment


                            #14
                            Originally posted by WaterH View Post

                            I converted to E-fans a long time ago. They helped at idle.



                            I have the orface tube for 134A. I also tried a "variable" orface tube. Someone on another forum said they were great. Didn't notice any differnce, so I went back to the fixed tube.



                            It's a thought. I would have to convert back. (Not a real big deal.) The issue is I have rode in other Broncos of the same period that would freeze you out. Why doesn't mine?



                            I have a bypass valve on my heater hose.

                            One thing I was wondering. I have headers. They are real close to thebox where the evaporator is. The air that goes through the evaporator immediately hits a plastic piece that turns it into the cab. It's like 6" to the headers from the plastic piece. This is stock. Has anybody covered that plastic with some kind of aluminum?
                            My dad's 89 blazer full size will freeze you out but it's got r12.

                            Comment


                              #15
                              Originally posted by Foxmxrcer View Post
                              Stupid question, did you put the proper amount of 134a in? I can't recall the formula... But it's like 85% of the r12 capacity or something.

                              Does the compressor cycle? What's your high side and low side pressures? They can tell you a lot about what going on....


                              Edit:

                              (R12 capacity X .9) - .25lbs = r134a capacity
                              Not stupid. Very common. But I have tried the proper amount, more than the proper amount and less than the proper amount. Slightly more than the proper amount seemed to be best. I got 40-50 low side and 200-250 high side. (Around 95 degrees)

                              Not sure about capacity because I have a condenser from a newer Bronco (134a) Not sure if it increases or decreases capacity.
                              Check out my project
                              https://irate4x4.com/general-4x4/2779-amphibious-hemtt

                              Comment

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