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1989 325is A/C Evaporator Temp Regulator + r134a Conversion Questions

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    1989 325is A/C Evaporator Temp Regulator + r134a Conversion Questions

    Hi guys,

    First post so I apologize if this gets posted in the wrong section. Anyways, I purchased my 1989 325is back in February after 3 long years of searching with a few small issues one of which being the A/C does not work. I thought that I could just live with it for a while and "just recharge it" when summer comes. Haha nope.

    With it being July now and wanting cold air, research is pointing me to just overhaul the system and get it converted to r134a so all the o-rings, dryer, pressure switch, expansion valve, possibly condenser, etc. would be replaced like in the r134a conversion posts on this forum unless if there is some other better refrigerant/option.

    Before I dive into this possible conversion however, I wanted to check if the compressor (model Denso 10P15E) clutch functioned. I knew the system was not working because the system pressure is too low so I bypassed the pressure switches thinking the clutch would kick in but got nothing. I checked the voltage there and wasn't getting any. Using one of the BMW electrical troubleshoot doc thingy, I traced it back to the Evaporator Temperature Regulator, jumped the connector there and got the clutch to kick on so the one issue lies there. If my research is correct, the temp regulator is connected to a thermometer and once the temp reaches 37 Fahrenheit, it turns the compressor clutch off to prevent evaporator icing.

    How important is this system? Could evaporator ice be a big problem? If it's not necessary, I would rather not replace the regulator and probe because they are quite expensive. Is there a good way of bypassing it or is that a dumb idea?

    Also, is the compressor I have r134a compatible? I am having a hard time confirming that. As for condensers, I know parallel flow condensers work better than our tube and fin but by how much will it decrease vent temp?

    Sorry if this post became a bit long or topics in this post have already been beaten to death. I swear I did some searching . Thanks in advance for any advice.

    #2
    As for the evaporator temperature sensor, I bypassed mine, seemed to go on and off on me. My vent temperatures don't seem to get any lower than he high 40s so I think I'll be good on the icing.

    The other thing to consider on your conversion is your hoses need to be converted to barrier hoses. I had a local hydraulic shop convert all but one of mine for $85. The last one I had to go to BMW.

    If you are going to all the effort of conversion, do it all and get the parallel flow condenser. As I recall, they are not that expensive.

    There is a good AC conversion DIY on this site.

    I can't help on the compressor.
    2004 525i Manual - 1985 325E Coupe Manual

    Comment


      #3
      Thanks for your reply. Yeah, I'll probably just refresh everything in the system that way no headaches down the road hopefully.

      As for the regulator, I might just bypass it and see if evaporator icing is an issue. How did you bypass your regulator? Jumper the connector?

      Also, if the evaporator were to ice up, would it cause any harm to the system or would it be that the a/c would stop cooling until it melts? The only time I see ice potentially being an issue would be when the a/c is used to dehumidify/defrost in winter time or driving through a thunderstorm where humidity is really high with an outside temp drop.

      Comment


        #4
        Originally posted by BaconMafia View Post
        How did you bypass your regulator? Jumper the connector?
        Yes, I made up a jumper wire.
        2004 525i Manual - 1985 325E Coupe Manual

        Comment


          #5
          Originally posted by BaconMafia
          How important is this system? Could evaporator ice be a big problem? If it's not necessary, I would rather not replace the regulator and probe because they are quite expensive. Is there a good way of bypassing it or is that a dumb idea?
          Not that important. The evaporator generally won’t get that cold unless you try to use your AC in late fall or winter. You can just buy solid copper wire and use that as a jumper between both connector ends, then seal it with electrical tape. I’ve done that on a couple of places on my car and no problem so far.

          Originally posted by BaconMafia
          Also, is the compressor I have r134a compatible? I am having a hard time confirming that. As for condensers, I know parallel flow condensers work better than our tube and fin but by how much will it decrease vent temp?
          It should be. The only E30s that had incompatible compressors were ones that came with certain Behr Bosch wingcell compressors.

          While a parallel flow condenser will help, I think the two most important things to getting ice cold AC are:
          1. Giving the AC system as little work to do as possible on a very hot (90-100 deg) day with lots of sunlight. The sun will put out 1000W of energy per square meter on a really good July day with a clear sky and you want to cut this number down as much as possible to slow down heat buildup in the cabin. You do this buy getting a somewhat dark tint with good infrared rejection installed. I’m running 3M Crystalline 70 all around, which supposedly does blocks out 50% of the sun’s total energy. However, it still lets in a lot of visible light (70%) which cooks the interior surfaces in short order; I just found out that visible light turns into infrared heat when it strikes the surface of an object. My E46 came with 20% tint on the rear and 45% tint on the front when I brought it and I noticed that the interior barely gets hot even when the car sits in the sun all day, especially the rear of the car. Tinting the windshield is illegal in almost all states, but if you go lighter on the windshield (50%-70%) cops won’t notice or care. Where I live a lot of cars have windshield tint; I think tinted windshields will be more accepted as electric cars become more mainstream and people look for ways to solve range issues with the AC on. Another thing you can do is put the AC on recirculate all the time.
          2. Remove as much heat from the condenser as possible. You do this by forcing the condenser fan to run on high all the times when the car is stationary. The easiest way to do this is to short the high speed temperature switch. Note that this will wear out the fan bearings faster.
          Last edited by ZeKahr; 07-04-2020, 09:03 AM.
          1986 325e Schwarz (sold)
          1989 325iX Alpineweiß​ (daily)


          Greed is Good

          Comment


            #6
            Originally posted by ZeKahr View Post


            2. Remove as much heat from the condenser as possible. You do this by forcing the condenser fan to run on high all the times when the car is stationary. The easiest way to do this is to short the high speed temperature switch. Note that this will wear out the fan bearings faster.
            One could switch around the radiator temp switch connectors to make the high speed fan kick in at lower temp or when the ac is on, instead of the low speed then high speed.

            Comment


              #7
              Thanks for the advice guys. I will look into window tint and aux fan bypass. I am currently in the middle of ordering parts for this. I will post the results of this a/c project if I remember.

              Comment


                #8
                Originally posted by BaconMafia View Post
                Thanks for the advice guys. I will look into window tint and aux fan bypass. I am currently in the middle of ordering parts for this. I will post the results of this a/c project if I remember.
                Definitely get the parallel flow condenser as part of your parts list. It is a lot more efficient and will help the system as a whole become more efficient.
                Originally posted by blunttech
                Levent guzzles vanilla hazelnut creamer like its my semen
                :shock:

                Comment


                  #9
                  Alright so some good news.

                  I did the a/c system refresh as discussed above and it works.....

                  However, with outside temps being in the low 90's, I only got vent temps in the 70's at idle and in the 50's while moving at highway speeds.

                  A/C was charged to about high 30's low 40's on the low side and a smidge above 100 on the high side. I would have liked to see higher on the high side so maybe the compressor is not 100%. Oh well.
                  It is certainly better than nothing but to get low vent temps, it seems I would need to go through the whole system which is big bucks.

                  Let us just hope it doesn't spring a leak lol

                  Comment


                    #10
                    Originally posted by S.J.1981 View Post

                    One could switch around the radiator temp switch connectors to make the high speed fan kick in at lower temp or when the ac is on, instead of the low speed then high speed.
                    Just tried switching the temp switch wires on my 86 325. Doesn’t work - the high and low speed temp switch prongs and connector terminals are different sizes. You need to use a jumper wire between the high speed temp switch connector terminals.
                    1986 325e Schwarz (sold)
                    1989 325iX Alpineweiß​ (daily)


                    Greed is Good

                    Comment

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