Intermittent then no hot air, '06 S40
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    1. #1
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      Intermittent then no hot air, '06 S40

      No, not what my wife would wish from me, and forgive me if this is in FAQs, but I'm about to run out the door and wanted to plant this. The first time I used the heater this year, I got off and on again warm air, only consistent if I cranked the output temp up to "full". It got worse, until this past week I get nothing but cold air, no matter if the temp control is set to "auto", somewhere in the middle of full on peanut roasting mode. I'm ruling out a heater core blockage as the coolant has been systematically changed at recommended intervals, the overflow tank level is always correct for operating and ambient temps, and the engine temp gauge never budges off the middle, so I'm also ruling out air pockets in the cooling system.
      My first question: does the Volvo "Auto climate control" unit have a self diagnosing feature? Most of the Japanese cars I worked on as a tech over a 30 year span did, and while it was never the end-all way to the fix, it was at least a good indicator of where I needed to look.
      Second question: anyone ever run into something similar? It's not particularly cold here (Central Texas) but it would be nice to use the defog without my nose getting frostbitten.
      I've seen similar issues with my Dodge trucks and if I recall, Lexus had an issue back in the late '90s, but it was two separate issues: broken mode doors for Dodge, and wonky control units in the Lexus, both very expensive. I'm not yet to the point where I don't fill the gas tank (it's got 266k miles) but I'm not anxious to drop a large chunk of change on this thing either.
      Thoughts?
      And thanks ahead of time.
      '06 S40 T5AWD M66: Mrs. Foley's old car.

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    3. #2
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      I had the same issue when I bought my used V50.

      Behind the waterfall, on the driver side, there is a small air vent-looking thingy on the panel. Right behind that is the “Cabin Air Temperature Sensor,” part number 3524841.

      Since I replaced that, I’ve had no issues.

      I bought mine from FCP Euro:

      https://www.fcpeuro.com/products/vol...sensor-3524841

      I’ve also pulled a couple from junk cars for some friends’ cars that have worked, too.

      If it’s not your heater core, this’d be my first guess.

      Good luck



      Sent from my iPhone using Tapatalk

    4. #3
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      Good info, thanks!
      '06 S40 T5AWD M66: Mrs. Foley's old car.

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    6. #4
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      So glad to see a potential solution to this. I have the same symptoms in my 06 V50. Luckily it has been a very mild winter so far here in Stockholm.

      Sent from my CLT-L29 using Tapatalk
      Last edited by woowar; 01-08-2020 at 01:13 PM.

    7. #5
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      Also, I forgot to mention, make sure that your external temp sensor is reading correctly (or close to it). That is a higher source of varying internal temp on the auto climate control.

      My climate control went wonky and kept going back and forth between A/C and heat when my external temp sensor failed. Part number: 30716713 (about $15).

      https://www.fcpeuro.com/products/vol...0-c30-30716713

      External sensor is located on the bottom of the driver-side mirror. First, remove the mirror:

      https://m.youtube.com/watch?v=ZlOmEGfRcqQ

      Then, look for the wire coming off of the bottom of the mirror casing. The sensor itself can be gently pried off to remove it, and the wire will need to have a couple of zip-tie type retainers opened, but it comes out pretty easily. I was able to use a small screwdriver to open the zip-ties and reuse the originals.

      Overall, this is a 30-40 minute job, most of it dealing with the sensor wires.

      Between these two repairs, it fixed my climate control fluctuations. They failed at different times in my car (previous owner beat the crap out of it), but check them both.

      Again, good luck!



      Sent from my iPhone using Tapatalk

    8. #6
      Before replacing the external temperature sensor unclip the connection at the driver's door, clean and deoxit the pins and socket, and replace the dielectric grease. Good chance that will fix odd readings.

      Granted, cheap as it is if you're getting other stuff fr FCP Euro, might as well get one in case it dies at some point.
      Last edited by silent-circuit; 01-08-2020 at 02:01 PM.
      06 S40 T5 AWD : DO88 intercooler : 3" EST downpipe : Eibach springs (1" drop) : Magnaflow cat-back exhaust : Hilton stage 2.5 tune

    9. #7
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      All good leads, thanks. I was on the road a while yesterday, and it sure acted like a plugged heater core: Hot when I first turned the temp up, ,then going gradually cooler. Before I left though, I pulled the inside temp sensor and blew a ton of lint out of it, and also noticed the rubber grommet was out of place, possibly causing the two wires to touch. It works just like a MAF sensor, so that would have been an issue. Once I get a chance to get under the hood when it's warm and actually put hands on the two coolant hoses in and out of the core, I'll know more.
      '06 S40 T5AWD M66: Mrs. Foley's old car.

    10. #8
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      [IMG]IMG_7832 by Russel Baer, on Flickr[/IMG]
      IMG_7831 by Russel Baer, on Flickr
      So if this works, the two pics are what happened when I grasped the top hose, which was warm by the way. I got part of a plastic coupler in my hand, and a bunch of nice, warm coolant. Just cuz, I lightly wiggled the other coupler, and it promptly broke too. It was quite a bit cooler than the top one, but if a heater core is flowing at the heat "on", I would expect some temp difference. After all, the core works just like a radiator, transferring heat to the air flowing through it, cooling the liquid inside it as it does. Anyway, I've now got a slight problem, as it appears the core itself has the same kind of couplers. I do hope the core itself is metal, other wise I would suspect it's just as brittle as the firewall-mounted coupler is/was. At this point in time, I'm not inclined to find out, since I'd sure hate to have it break too.
      Good news: since I had ready access to the heater hoses, I grabbed the garden hose and ran water into each hose in turn, and the flow out was the same as the flow in, no pressure buildup, so I guess the core is largely unrestricted.
      Feel free to laugh, I am. I'm also glad it broke in my driveway, and not on the road somewhere.
      '06 S40 T5AWD M66: Mrs. Foley's old car.

    11. #9
      Yeah heater core is low grade aluminum. Low. grade. Low.
      2006 Volvo S40 AWD T5 M66 - Dusty Rusty
      2012 Subaru Outback 2.5i CVT - Slowmobile - CAI only, Powerstop Rotors+Pads.
      1996 HD Electra Glide - Big Bertha - 10:1 Wisecos; EV13 Cam: Ultima Digital Ignition; Buell Head Conversion; E85 Carb Tuned;

    12. #10
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      At least it's not plastic...... The word from my buddy that runs the franchise shop that does the work I can't do anymore: $200 out the door, so I'm okay. It needed a coolant flush anyway.
      It was kind of odd, watching the car go away on the back of a flatbed. At 267k miles, this was the first time.
      '06 S40 T5AWD M66: Mrs. Foley's old car.

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