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Thread: Heating/Cooling Question

  1. #1
    Join Date
    Aug 2017
    Location
    Mount Plymouth, FL, USA
    Posts
    24
    My Cars
    1987 BMW 325i, 1997 BMW

    Heating/Cooling Question

    This past weekend I have installed a new compressor in my A/C System (new drier, new parallel flow condenser, rebuild A/C lines that are R134a compatible etc.).... . The pressures were good according to the chart that my Dad used... And his gages are good quality gages... We have no leaks ( the charge has held up fine this entire week) ... but we noticed that the when the ambient temperature was around 82 degrees... the temperature in the center vent with the fan on hi (and A/C going) was 65 to 68 ....

    Dad felt that it should be a bit lower.......

    Now... here is MORE data.

    When I was driving the car this morning (with the top down and the A/C OFF) .... I noticed that the ambient temperature was around 59 degrees in the AIR STREAM, using the onboard computer reading (and the meat thermometer we use to sample the vent read the same - so they both agree) ..... I put the thermometer into the vent and ran the fan on HI.... and noticed that THAT temperature was about 10 degrees higher (70 degrees) ... Throughout my drive to church this morning the VENT temperature was 10 degrees higher than ambient. The Heater Control valve was set all the way clockwise.... on COOL.... and when I DID turn the valve all the way to HOT ... that run up to about 140 degrees... So the valve works.

    Can you guys tell me if this is NORMAL for the vent temperature to always run 10 degrees above ambient? When I am running my A/C .. is it having to fight with the heater core being hot? Do you maybe think that my heater control valve is old and leaky? Or is this just the way this car works normally?

    I guess I am wondering if you guys also see this on your cars.... OR do I need to think about heater valve replacement ... This is a 1987 car with 240,000 miles on it..... and it has never had really cold A/C.

    Am I obsessing over this?

    Thank you in advance for comments.

  2. #2
    Join Date
    Dec 2005
    Location
    corpus christi, texas
    Posts
    6,738
    My Cars
    No e30s, again :(
    my son's 86 325 has about 46 at the vents. we put the meat thermometer in the center gage to read from
    No e30s again.

  3. #3
    Join Date
    May 2010
    Location
    Officially in Tampa
    Posts
    2,137
    My Cars
    87 Cabrio & 87 ETA
    The heater valve shouldn't effect your AC since the temp dial controls a blend flap that diverts air from your heater core to your evaporator. Keep in mind that vent temps are very relative. What you're really looking for is the temp differential between ambient and thand vents. BMW (and most AC techs) suggest 18-21 degree as being on spec although I've had systems run as much as 40 degrees difference. Vehicle and engine speed will effect these as will humidity (big time).

    Is your auxiliary fan working ?
    did you change the drier when you evacuated the system ?
    How about the expansion valve ?

    what I've learned recently after buying about $500 worth of HVAC tools (including a micron guage) and wrestling with an e30 I rescued is that usuing a manifold to assess vacuum is useless. You need to get below 1000 microns which is 1/10". No way to read that on a guage that shows 0-30 in a linear inch.
    87 Zinno Cabrio 98k Barn Find. Build thread http://www.r3vlimited.com/board/showthread.php?t=268987
    87 Lachsilber ETA Time Capsule. bought w 125k from 87yo original owner

    Cabrio deck lid & hinge struts (w sleeves) now for sale. See the link below for more info

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  4. #4
    Join Date
    Jul 2013
    Location
    CT
    Posts
    434
    My Cars
    1989 325i 4 Door 5sp
    Im following in your footsteps with the conversion. Can you tell me which condenser you used and why you replaced instead of rebuilt?


    Sent from my iPhone using Tapatalk

  5. #5
    Join Date
    Aug 2017
    Location
    Mount Plymouth, FL, USA
    Posts
    24
    My Cars
    1987 BMW 325i, 1997 BMW
    Hi,

    Aux fan is working...... new drier.....expansion valve was not replaced..... the condenser was of the parallel flow type (new)....

    I just thought that since I was reading warm air coming from the vents when the heater control was fully counter clockwise.... that this was fighting what little efficiency the A/C system has.....

    If this is normal for the car.... maybe it is as it should be... and I should stop fretting about the A/C not being as robust as newer vehicles....?

    I never know when to quit.

  6. #6
    Join Date
    Aug 2017
    Location
    Mount Plymouth, FL, USA
    Posts
    24
    My Cars
    1987 BMW 325i, 1997 BMW
    Hi,

    I choose a parallel flow condenser because the guys on this list advised that a parallel flow unit would not clog up as easily as a serial flow type. I bought it from Rock Auto.... I do not remember the actual type... it has been a while... I started this work before the winter set in... and only just now am finishing up..... I also "tried" Duracool R-12a ...... but this was when my compressor was on it's last legs.... so I did not get a fair chance to test it.... I put the stuff in and my compressor died. It was only 15 years old.

    Anyhow.... This car (when the A/C was working) was never very cold..... I had a conversion installed years ago... and when they did it... they did not change out the hoses.... (which I only recently found out were not R-134a compatible.... the material was meant for the old R-12 coolant.... and R-134a was able to slowly leak through the hose material..... I was always putting in gas.. and it would not last long. I recently had the hoses rebuilt to new specs for R-134.... So we will see if it holds a charge for longer than the summer this time. Florida can be HOT and HUMID..... and frankly I just need to put this car away for the high summer and use it spring, fall and winter.

    Clark

  7. #7
    Join Date
    Dec 2005
    Location
    corpus christi, texas
    Posts
    6,738
    My Cars
    No e30s, again :(
    your ac should work fine, its not an issue that its older. on all the e30s I had with working ac, it froze you out so something is wrong. I don't know why those center vents are warmer than the rest but I would take the center console out (around the shifter and ashtray) and check whats going on. like I mentioned earlier, my son's 86 is freezing and I have to turn the ac down while driving so its not the ac is just naturally warmer.

    we used a different refrigerant though so maybe that is also helping us. we used propane
    No e30s again.

  8. #8
    Join Date
    Jul 2013
    Location
    CT
    Posts
    434
    My Cars
    1989 325i 4 Door 5sp
    Oops I meant to ask which COMPRESSOR you used... not condensor

  9. #9
    Join Date
    Aug 2017
    Location
    Mount Plymouth, FL, USA
    Posts
    24
    My Cars
    1987 BMW 325i, 1997 BMW
    This is what I got from Rock Auto

    https://www.rockauto.com/en/moreinfo...011676&jsn=390

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