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Thread: Please help me to diagnose what the indy shop did wrong with my AC repair

  1. #1
    Join Date
    May 2007
    Location
    South Florida
    Posts
    84
    My Cars
    2010 335xi

    Please help me to diagnose what the indy shop did wrong with my AC repair

    Hi, all. I'm posting here in the hopes that y'all can help me to figure out just what the heck happened to my AC and whether this is due to a faulty repair by the indy shop that did the work.

    My car's AC was only blowing out tepid air for the longest time. I kept getting it recharged but that didn't last long. I finally had it repaired and here is the work the shop billed me for:

    1 Evaporator (no further detail provided)
    4 O-Rings (no further detail)
    Evaporator core (replacement)
    R134a refrigerant
    Recharge heating and air conditioning

    All this work cost me $2,100, and based on how they explained what was involved I figured it was a reasonable price. They had the car for six days.

    After the repair, the AC started working great. It was so nice to have cold AC during the hot South Florida summer! However, right away (in fact on the way home when I picked up the car), I noticed that hot air was blowing from the lower vent around my feet while cold air was blowing from the mid and upper vents as expected. I called the shop and explained the situation, and they had me bring it back in, which I eventually did. I don't know what they did when I brought it back in, but I suspect they didn't do anything and couldn't replicate the issue, as I've since realized that it only becomes noticeable once the engine gets really warmed up, and my shop is close enough that I don't think it really did.

    After a lot of investigation on my part, here is what I have found:

    The lower vent does blow out moderately cool (I don't say cold) air once the car is started and the AC is engaged.
    The issue with warm air coming out of the lower vent only starts to happen when the engine temp gauge reads about 190 and becomes more noticeable as the engine temp increases.
    The issue with the lower vents blowing warm to hot air occurs both on driver and passenger side vents.

    Scenarios once engine is warmed up and temp gauge reads at least 190
    1. Climate control set to Auto with cabin temp set between 70-75 (I tested at each temp) and air volume (fan) set to low to mid bars
    Middle and upper vents blow out cold air with sufficient volume, as expected
    Lower vent starts to very lightly put out cool to tepid air, but then eventually starts blowing warm to hot air.

    2. Cabin temp set to low to mid 70s (again, tested at various temps) with only lower vent engaged, and with engine temp at least 190
    Same outcome as above, only warm to hot air blows, and turning up air volume only makes it blow more warm/hot air.

    3. Climate control set to Auto with cabin temp set to 68 and air volume (fan) set mid to high
    Cold air blows from middle and upper vents with expected force
    Cool air (I won't say cold) lightly blows from lower vents

    4. Max AC button set with only lower vent engaged
    Cool air comes out forcefully from lower vent but not as cold as expected.

    I never had this issue before the AC was repaired so I can only assume it was something done by the indy shop but I don't know, and they seem unwilling to put in the work to figure it out. And on a side note, sorry but if a shop charges me $2,100 for a repair and then breaks my cup holder assembly, they shouldn't just shrug it off and tell me how cheap those parts are and then give me a quote for a new one!

    Overall, this shop has done good work in the past but I think they were just in over their heads on this repair- or at least the guy doing the work was.

    I'm hoping that y'all can help me to understand exactly what the issue is so that I can go back to them with this info to get them to repair it. Or explain to me that it's something else and was just a coincidence that it happened right as I got my AC repaired (you'll have a tough time convincing me of that, though).

    I've tried to put in all the info I can think of, but if there are any questions, or if I can provide any further info, please let me know.

    Thanks, everyone!

  2. #2
    Join Date
    Jul 2011
    Location
    Arlington, VA
    Posts
    9,933
    My Cars
    2018 BMW M240i
    The automatic climate control module (IHKA in BMWspeak) controls a bunch of stuff in the dash and the heater control valve in the engine bay. The IHKA is basically a computer. They rarely go bad.
    If you’re getting warm air in the footwell the heater control valve is being opened by the IHKA or the valve is “leaking” and allowing coolant to flow through the heater core. Btw, the heater core sits directly underneath the AC evaporator. Why? The evap has 2 temperature sensors that send data to the IHKA. If either of those sensors tell the IHKA that the evap’s temperature is below a specific temperature the IHKA will open the heater control valve to prevent the evap from freezing.

    So what to do? The heater control valve sits on the left front (drivers side) metal inner fender. It had as 2 smallish hoses and an electrical connector at the top. The valve is open unless the IHKA is sending it 12VDC. In your case the valve should be closed.

    A few questions:
    1. What’s the maintenance history of the cooling system?
    2. How frequently is the coolant changed? I ignore the “5 year coolant” and change it every 3 years. Just had the dealer change it on my current car, an M240i. I owned an e46 for 17 years.
    3. Does your gauge cluster accurately (+/- 3 degrees) show the outside air temperature?

    I’m betting that the heater control valve is corroded and not fully closing.

    How handy are you with working on the car? Do you have some basic quality (minimum Craftsman) tools? If you want to change the heater control valve go to www.realoem.com and enter the last 7 characters of your car’s VIN. Hit enter and bookmark the page. Scroll down to radiator. You’ll find the part # for the valve. Then go to FCPEuro to buy the valve that’s labeled “OE” (original equipment).

    The installation of aftermarket cooling system parts is strictly verboten.

    Why FCPEuro? Lifetime warranty on everything it sells. Great prices and fast shipping.

    With the car cold clamp off the 2 hoses on the valve. Disconnect the electrical connector and the hoses. Remove the valve and install the new valve. Reconnect the hoses only! Remove the clamps. Start the engine and make sure you done have any leaks. Leaving the electrical connector off will open the valve and allow coolant and any air to flow through the heater core and back to the expansion tank at the radiator. Wait until the hoses on the valve are hot before shutting the engine off. Then reconnect the electrical connector to the valve. Try the AC realizing that the heater core will be hot for a while.

  3. #3
    Join Date
    Jan 2016
    Location
    Ca
    Posts
    6,981
    My Cars
    2001 525it
    You need to go back to the shop, they need to find out what is happening they just had the whole dashboard and center console apart, no charge. It’s not up to you to figure out what’s going on, they just worked on the car

  4. #4
    Join Date
    May 2007
    Location
    South Florida
    Posts
    84
    My Cars
    2010 335xi
    Thanks so much MarcoZandrini! That is the kind of info I was hoping for, as I feel I need to spell out the issue for the shop for them. However, I imagine getting them to take responsibility and do the repair for free will, unfortunately, probably be another story.

    To answer your questions:
    1. Maintenance history of the cooling system- Beyond having the evaporator core replaced recently, I can't answer that. I assume that whatever service was needed was done when I've taken the car in for regular maintenance when needed. There hasn't been a major repair to it before this one, if that's what you're asking.
    2. Coolant change- Same as above, I assume it was done as needed during maintenance. I guess I would have to look through my records to see when it was last done.
    3. Gauge cluster and outside temp- Yes, the temp displayed on the dashboard is quite accurate in my estimation.

    Jclausen- In a perfect world, yes, that would be the answer. And it's my hope that now that I've explained exactly what the issue is, the shop will stand behind their work and figure out the problem and fix it. I just don't have faith in that happening, but I hope I'm proven wrong.

  5. #5
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    Sounds to me like the evaporator/heater flap isn't working, and/or the heater control valve is bad, and frozen in the open position.

    Given that this is a new issue, concurrent witht the repair, the flap is almost certainly the problem.

    It's possible that the motor for this flap just isn't plugged in....or the control rod which attaches to that motor is detached or jammed....OR, the flap itself is incorrectly installed, and jammed.

    The last scenario is a disaster -- for the guy who did the job -- because the entire job will have to be redone, with everything coming out and apart again. (11 hours!)

    Take the car back to the shop immediately, and tell them, politely but firmly, that you want the problem corrected. Make sure to keep notes of every interaction and discussion with the shop.

    Did you pay for the job by credit card?

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  6. #6
    Join Date
    May 2007
    Location
    South Florida
    Posts
    84
    My Cars
    2010 335xi
    Thanks so much, bmwdirtracer! Great and very useful feedback!

    Yes, I paid by credit card back in June when the repair was first done.

  7. #7
    Join Date
    Jan 2016
    Location
    Ca
    Posts
    6,981
    My Cars
    2001 525it
    If you don’t have faith in the shop that did the work and who will back up there work you need to find a better shop it’s on them they owe you a working system

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