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Pro Air A/C unit on my new to me 2012 Merc Sprinter Van

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  • Pro Air A/C unit on my new to me 2012 Merc Sprinter Van

    Hello All,

    My Pro Air unit put in the vehicle by Pro Air Inc. out of Elkhart doesn't cool very well. Vehicle sat in a consignment shop for 1 year and I purchased it Feb 2018 with 26K miles so not much work out of the unit. They put the condenser with 3 fans under the middle back of the vehicle and run the cooling lines with the heater core lines; there is a stop valve for the heater lines just past the drivers seat under the vehicle. These vans already put off a lot of heat from the engine alone. It has its own pump and all the other car AC parts, but all this is run from the engine pump passenger side under the front of the engine then follows under driver seat all the way to the back.

    With ambient temp 93 currently it will only cool the air out of the blower to 68-72. Gauges on it show low side 30 and high side 194. Pump clutch engages appropriately, condenser fans (all 3 work), cleaned condenser (was not that dirty) etc. Front sticker states it holds 72 oz R134a. I slowly put in 40 oz over 30 of R 134a letting it sit 10 minutes and run between charges. The low side pressure increases to 50-60 while charging the high side increases 1-2 to around 196 or 198 with charging. Then when you stop charging and let it run numbers return to low 30 and high 194. The cooling did not get much better maybe now it is 68 instead of 72.

    Question is showed I trust the gauges and continue to add assuming it had leaked out... but with initial pressures of 30 and 194 I would think it had some R134a in it.?

    Or should I add some R134a with dye and keep going to see if I the high side will increase to 230-260 based on my ambient temp?

    Or should I discharge and vacuum it down to see if it holds the vaccum?

    Or is there a part in the equation I am missing?

    Or can it not cool well because of ALL the heat around it?

    Thank you

  • #2
    Welcome Eric: I'm totally unfamiliar with this vehicle somehow and don't understand condensers being place mid cabin guessing a mid engine van. If this is pre engineered to work this way the incoming air for condenser really has to be real ambient air not really much or any engine heat involved while running so far confused just how that design is?

    So, the charge is listed must have once worked the real ambient temp measure for this or any really is what air temp is coming in perhaps a foot in front of condenser is what the high side thinks it's dealing with. Correct if right about 93F times 2.5 (rough idea) of that at a raised idle say 1,500.

    You know a capacity listed not sure how you are weighing in that exact amount if this ever worked. One issue is unclear that you stopping charging at 30oz. of 72oz listed and waited? Not good to do that and shouldn't have to if charging into a well held vacuum of a 72oz. system would expect first 30oz would dispense without engine running at all or totally better to have equipment that just pushes in the spec # of ounces without engine help at all then get it running and do checks if not as expected.

    Limited experience by me on alternate engine locations to just VW's Vanagon, rear engine condenser was all the way up front thru a grille well fanned. Super long lines by the layout and HUGE interior space was the real only vehicle I could not tweak to lower than I think was very low 50s at about that day's temp for ambient hotter sitting still. No choice on my part with that one for longer time or test drives at all believe it was at least adequate for what it was and that layout probably did just OK out on the road or at least didn't hear back it wasn't good enough was done by me at another shop that gave up!

    Seems all I keep saying here is running A/C with low charges some will or forced oils don't move until there's clearly cool out of best vent for it inside if too long running dry you can wipe out a new compressor right away! Should be spun with oil by hand if need be off vehicle totally.

    Sorry for another long reply. Need to more on just what was replaced and why other than just time sitting and how you vacuumed and began this charge with what parts new not just a company that makes them doesn't tell me which ones,
    MetroWest, Boston


    • #3
      Thank you for such a quick response Tom!

      This is an accessory unit put on this Long High Top (large interior space) Mercedes Sprinter van. It has the primary unit that comes stock on all these sprinters. So the company that originally built the van for a pro football player had the local Pro Air Inc place an accessory AC system on the van to help with heating and cooling the space. So I have no idea how it really worked when they first put it on in probably early 2013 in Indiana with ambient temps of winter weather (it probably tested out well).

      I have not evacuated it yet because I thought based on my low and high side numbers being low that it was just low and since everything else seemed to look good except for the temp out of the registers I felt that charging with almost half the amount that the Pro Air sticker says it requires (72 oz) would be a start. I can continue to add but I feel like it should have had some R134a in it unless it all leaked out since installed, which is obviously possible.

      I believe that the temp the condenser is seeing is a lot higher currently because if my ambient temp is mid 90s currently, with the engine heat blowing back and the baked asphalt and concrete I would think the condenser may be seeing 130 or more.?

      So what I was wondering since I have not evacuated it is since my gauges are reading low for ambient temp and my air from the registers is not very cool (68 at best) should I just add more R134a with dye in it now up to what the Pro Air sticker says the system holds as long as my pressures don't get above normal for ambient temp OR should I evacuate the system, pull a vacuum see if it holds then add back the 72 oz with some dye. And are there any other components on a regular car AC system that could be causing my lower high and low side readings with a high register temp output?

      Thank you


      • #4
        I think your options are to add R134a containing dye (NO SEALERS) and the look for a leak with UV light/goggles/dark. Or have a real AC shop recover and weigh your refrigerant in the system and look for leaks. 194 psi on high side at about 1500 rpm seems low, and indicates not fully charged; and if low, indicates a leak.


        • #5
          OK, Eric. I'll post a link below for charging procedures some links within it will not work or may? If I missed it, sorry. Even this is the final charge up without the insane buck equipment. All require you begin knowing it held a full maximum vacuum best a couple hours. By gauges at sea level is 29.92 adjust that # down 1 point for each 1,000 ft. of altitude I don't think Missouri has much of anywhere over that could be wrong?

          If in switching small cans is what you are doing they must be warmed up as they go cold too quick. Use warm water you can touch not super hot water. That or a 30lb. tank still can need warming if not full and warm to begin with. Watch out and bleed lines of air the enemy of anything A/C #s and pressure will not behave nor be accurate.

          You must weight containers, tare weight with gauges or hoses on and do the match how much really is in the system. Pressures alone are good for diagnosing are not as good as knowing you have the correct charge is all important.

          Cusser is a pro BTW so help is here. I was instantly thrown off as subject line "Merc" to me means a MERCURY (FORD) product and if only me use "MB" for the Mercedes.

          This is in archives here for a pretty good procedure to follow by "Nacho" is a member here not here much could maybe help thru a private message may totally know the unit you are dealing with and any special quirks about it.

          So far if not missing something this is plain low on charge.

          Side note: I'm in Massachusetts West of Boston about 200 miles North of New York City if only helps understand what I would deal with at this location. 232 altitude (irrelevant) mostly. Temp ranges for here are within norms annually to see -10F to 110F is 93F now expecting perhaps 105F tomorrow only a day. Will be humid, that matters too but only does that short spells to excess.

          Right now 134a isn't all that costly if you lose it suggestions by Cusser remain. Use dye just anyway it should stay in the system unless flushed totally out.

          Question on this unit? Does it take in air for HUGE van space from inside (recirculate) or always outside air? Can't know but even if this unit doesn't freeze you out the vent temps measured should still blow cool air and it isn't even close now. Read link below...….

          > http://autoforums.carjunky.com/Autom...YSTEMS_P45460/ <
          MetroWest, Boston


          • #6
            Many of the Sprinter are converted into RV's. Lets see if I'm understanding this right. The aux condenser is UNDER the van? I agree there will be a lot of "road heat" down there.
            I agree with others, in that I think it would be best to pull it down, look for leaks and put the correct amount of refrigerant in.
            Does it use a separate compressor from the factory system?
            The problem I see with just adding is you never know where your at. By going with the correct charge and then looking at the pressures, you have a baseline to diagnose from, without that baseline, you could end up chasing your tail.
            If it has a big enough condenser, it can handle the excess heat, but along with the heat it gets road spray in the winter and that will degrade a condenser real quick. The RV conversions put the condenser on the roof, which would have been my choice.
            A/C hose is thick rubber and insolates the refrigerant from the outside temp, if steel line is used, that would not be the case, and I could see it picking up heat from the engine if nearby.
            I would tend to think you are still low, based on the pressures alone, but you really can't tell. If you really want to try, you can add more, but I'd look over the system carefully for a sight glass, that would help. When I worked on shuttle buses, they often had remote sight glasses and moisture indicators in the liquid line.
            Until there is enough liquid refrigerant to make it all they way thru the evaporator, the low pressure will be based on the ability of the compressor to pull vapor, and the metering device to flow vapor thru it, so more or less meaningless. The high pressure will be the condensing temp, but if not much heat is absorbed in the evaporator, the condensing temp will not be that high.
            Last edited by Cornbinder89; 06-17-2018, 02:37 PM. Reason: more info


            • Tom Greenleaf
              Tom Greenleaf commented
              Editing a comment
              Great thoughts. I forgot about looking for a sight glass!

          • #7
            Thank you all for your information and help thus far....

            I will take apart the back upper part of the van tomorrow to see how they installed the evaporator and blower (I was thinking about that yesterday as to whether it is recirculated air or outside air); I also wanted to see if they insulated the evaporator in the ceiling or is it using super heated sun baked air up there. I speculate it is enclosed well and uses recirculated air due to what looks like 2 return vents.

            Aux condenser is under the van a little past the middle offset on the drivers side due to drive shaft and it is about 3.5 feet long by 1.5 feet wide. It has a separate compressor but it does not look like the factory one. I feel like they put this one underneath to keep the height lower so it could fit under smaller spaces. The AC hose is a thick rubber hose from the engine compartment back, there is some open "steel" but not much.

            I read (don't know if it is true) that the SAE designed the A/C fittings to have an acceptable leakage rate of 1/4 oz of refrigerant per year per fitting with an average vehicle having 8 fittings. If that is true with all the fittings on this accessory A/C unit over the 6 year life of this vehicle with low use (worse on the vehicle) I bet it could have lost more that half or greater of the refrigerant.

            I like the nickname Cusser it made me laugh not sure who the picture is; but since the equipment all seems to be working as it should and the pressures are consistent with LOW refrigerant I think I will add some dye and more refrigerant (after looking for a sight glass per cornbinder89) and see if I can get the pressures up to normal for my ambient temp and the evaporator to blow cold air (from looking this thing over it really should freeze you out in there). Then look for some dye after I run it a bit for a leak. Since the unit has such low miles and sat for a year in a consignment shop with little use it is possible some seals dried out etc. and maybe it has a leak that I can find easily. This I believe is the under body mounted condenser I have.

            Condenser 110 - 50 000 881
            Frkg, 110 condenser

            BTU Cooling 60,000 / CFM 2,940

            24 amps @ 12 volts (30Amps@14v) / Size 44.5"x13"x13" / 33lbs


            • #8
              This I believe is the evaporator tucked up in the back but I will find out tomorrow.

              Frkg. 560 Heat and Cool, Free-Blow with Cover

              Cooling BTU 30,000/CFM550 Heating BTU 32,000/CFM 550

              21 Amps @ 12 Volts / Size 8.5x32x15.5 / 36lbs


              • #9
                Originally posted by Tom Greenleaf
                Cusser is a pro BTW so help is here. I was instantly thrown off as subject line "Merc" to me means a MERCURY (FORD) product and if only me use "MB" for the Mercedes.
                I'm not really an AC pro, but do have some AC experience, comes with the territory of living in Phoenix for many decades.

                Originally posted by Eric
                I like the nickname Cusser it made me laugh not sure who the picture is
                That's Mrs. Cusser, guess she forgot her knickers that day. Anyway, we're all older now !!!


                • #10
                  Some years back my uncle picked me up at the Phoenix airport, his rear view mirror in his car had fallen off, the dashboard was warped. I asked him what happened to his car he said its Phoenix main its "expletives" hot!

                  So I added dye and 12 oz r134a....pressures at 1500 rpm low 20 high 225; at idle 650 rpm low 35 high 195. Where the evaporator was placed back upper van the distance between the air vents that you see in the cabin and the actual evaporator fan/vent is 1 foot and not completely sealed. The temp out of the evaporator is 63 and out of the cabin vent is 68 so a loss of 5 degrees in a foot. Underneath the van at the condenser there is a drier off the condenser (with pressure switch - the clutch did NOT disengage when my low pressure reads 20). I looked the whole system over and everything really looks good, long run from the front compressor to the evaporator, lines sweating underneath, drains a lot of water from the evaporator catch pan out both sides from lines to the ground. I feel like it should cool much better, really well.

                  The pressures at 1500 rpm after the 12 oz of refrigerant (low 20 and high 225) would lead me to believe a restriction somewhere (expansion valve/ orifice tube) but I don't see one...past the drier it looks like just a hose straight shot to the evaporator hook up (there is a strech of hose I can't see when it heads up to the evaporator). I put a call into the tech support guy at the company. The other thing I thought is would the evaporator itself have the expansion valve or orifice tube built into it? Also, could the condenser be to big for the evaporator and my bottle neck is really the evaporator; but wouldn't the larger condenser with a smaller evaporator just allow the evaporator to work better. Shouldn't an evaporator in the shade with recirulating air be able to cool it down to at least 40 out of the actual evaporator vent?


                  • #11
                    Ok, your 225 PSI high side say condensing temp of 135-140 deg F, does that seam about what the outlet line of the condenser is at? On a Tx system the receiver is on the high side along with the pressure switch so WILL NOT CYCLE with a low charge, it will shut it down or not start it if the system is low.
                    lot of condensation says something is getting cool somewhere to below the dew point of the air.
                    Re fresh my memory, how much have you added in total?
                    It almost sound like air is bypassing the evaporator and not going thru it. Try and get a "fin temp" on the evaporator itself


                    • #12
                      If a condenser is "too big" it will just store liquid refrigerant after it condenses and it will cool the liquid below the condensing temp, so all it will do is make the system work better. I have a 3 ton condenser on a 2 ton system at it keeps the head pressure low and the system working at its best even if conditions aren't ideal.


                      • #13

                        The condensing temperature of about 135-140 F would be accurate (thus outlet line). Understood on the switch. The lines getting cool...when i feel the left (input) side of the evaporator the lines feel really cold. When I looked of the box built around the evaporator I feel like they did a poor job because....the 4 vent outputs where the blowers are all blew are forward to the cabin outlets 1 foot away but all have a 3/4 to 1 inch gap just off the evaporator blowers that blows air into the big box space built around the eavporator. The intake (back) of the evaporator then pulls air from the big box it is in which consists of hotter air because it is so close the roof as well as cooler air just out of the evaporator and cabin air (all technically is recircuated air but kind of not. Fin temp on the intake of the evaporator after it was running for 15 minutes was 90 degrees still with direct output temp at 1500 rpms 63-64.

                        I talked with a long time tech at the company....he felt like the pressures at 1500 rpm of 20/225 were okay for the humity and ambient temps we are having. He did say it has an expansion block that the lines connect to on the inlet of the evaporator that unbolts. He felt like the refrigerant was still low and asked me such in several ways. To your point on how much R134a in have put in it now (72 oz) that is what the company has written on the sticker for the total volume needed. I will be driving it around tonight and see if the temp changes at all. You stated that "it almost seems like the air is bypassing the evaporator"....since they did not frame up the intake port to pull from the two pretty cabin return vents on the ceiling it is just pulling from the box that was built around it albeit from behind (box is approximately 18x larger than the evaporator, it all still inside the cabin. I was able to seal the output gap of the blower about 80 % (the top part will be hard to seal but I will get to it.


                        • #14
                          90 deg fin temp? How can that be if the output is 63-64? Both evaporator lines into the block type Tx valve should be about the same temp, if the inlet line is colder then the outlet, AND you know you have correct charge, points to a bad Tx. If the line from the condenser to the Tx is cool or cold, then you have a restriction between the condenser and Tx.
                          One possibility is the desiccant bag in the drier has come a part and the desiccant beads have traveled to the Tx.
                          As to amount, you have added 72oz or you recharged to 72oz or what?

                          When I worked on mini-bus conversion vans, I was surprised by the poor quality of the retro-fit components. It seamed like everything was "good enough" to make it off the sales lot and not much else.


                          • #15
                            By fin temp you mean the fins at the back of the evaporator where air is being pulled through into the evaporator.?

                            I will have to measure the inlet and outlet line temps.

                            I have added 72 oz with uv dye, I am assuming (i know) it has a leak somewhere, shortly I am just going to buy a new expansion valve and drier and evacuate it all down and restart.

                            I will check the lines for temp. to see if those pan out per your statement.

                            I would not doubt that some of the equipment is of lesser value... i believe this is the drier on my rig, it was made in china and I don't know the quality name products.


                            • #16
                              Quality - What's that? You (customer) are the test lab.
                              BTW that probably has a sight glass on top unseen in your picture.
                              You read it like this look for better in color or videos as needed if unsure.
                              Crude basics like this,

                              This is read while operating at a raised idle,
                              Last edited by Tom Greenleaf; 06-19-2018, 12:43 AM. Reason: Pics not showing
                              MetroWest, Boston