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  • Heating problems B5 A4

    Ok, so i have aan annoying problem with my A4.. Occasionaly the heating stops working, if i go from LO (17 degrees) to say 24 it gets ever so slightly warmer, but not even luke warm... Unless i go up to HI (30 degrees) then it blasts out heat. Even if i go from HI to 29 it almost goes ice cold again. Whats wrong? It seems to do this more often when outside/ambient temp is warm like today when it was around 18c while driving... Havent checked any faultcodes and as it is a 2001 B5 it has the newer klima controll and i dont know if it is possible to diagnose through that. Any tips are appreciated.
    Audi 80 Competition -94 Daily driver

    www.garaget.org/fish for more pic´s of my cars

  • #2
    there is a known heating problem by audi 80 b4 typ and audi a4 that the little heating radiator inside the ventilationbox is getting clogged,no circulation at all
    You can try flushing it with a garden hose
    or try a cooling water flushing agent
    audi coupe quattro b2 2.2 20vt project (573hp-626nm)
    TWINCHARGED power,zero lag
    AEM W/M injection

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    • #3
      Forgot to mention i flushed it last year... Might be time to reflush it though. But if it would be clogged, then i suppose i shouldnt have any heating when i put in on HI? If it's on HI i get good heating.
      Audi 80 Competition -94 Daily driver

      www.garaget.org/fish for more pic´s of my cars

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      • #4
        check live data with a scan tool,

        see what the internal and external temp sensors are reading before getting mechanical
        1993 URS4 Avant Emerald Green 350+bhp
        1991 Ford Sierra Sapphire 4x4 in Magenta
        BoooOOOSSSSSTTTT BANG BANG CHIRP CHIRP

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        • #5
          External tempsensor? As in outside temp? Or am i being an idiot now?
          Audi 80 Competition -94 Daily driver

          www.garaget.org/fish for more pic´s of my cars

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          • #6
            Outside temp sensors on B5s often go wrong cos they're mounted just behind the lower rad grill.
            Last edited by newsh; 22 April 2014, 00:09.

            S2 Coupe 3B Project


            Ur quattro restoration

            S2 Avant

            Boost is the new rock and roll!
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            • #7
              Your internal temperature sensor - the one behind the grill just above the climate control unit - is blocked by dust or the fan behind it that draws the cabin air over it has failed.

              John

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              • #8
                Is the front facia (in my case wood look) just clipped on? Have heard about that fan/sensor before... When should the fan be activated? Or is it activated as soon as ignition is on?
                Audi 80 Competition -94 Daily driver

                www.garaget.org/fish for more pic´s of my cars

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                • #9
                  Originally posted by fish View Post
                  Is the front facia (in my case wood look) just clipped on? Have heard about that fan/sensor before... When should the fan be activated? Or is it activated as soon as ignition is on?
                  Not certain about the wood facia, but I believe it is just clipped on. The fan for the interior temperature sensor is driven by the Climate Control Unit and I believe is on whenever the CCU is on.

                  John

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                  • #10
                    That would be my guess. Clogged with fluff and dust..vcds will tell you if you have a problem. The other fault is the motors controlling the flaps stick due to dirt build up, excercising them on output tests sometimes works.

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                    • #11
                      Hi

                      Just went trough something similar on my B4 climate.

                      I reckon 90% it's a partially blocked heater matrix, why partially?
                      On mine the cold/not hot air issue was more from the lower ducts and less on the upper ones.
                      This depends on where the ducts are connected on the main central door on the air box.
                      If you have a noticeable (hands should be sufficient) difference of temperature from the three grids/vents on the dash
                      I.E. central (colder) grids and left (warmer) and right (warmer then the left) then the lower part ot your heater matrix it's blocked.

                      The temperature flap on the airbox deviates the air blow against or faraway from the heater matrix.
                      Then if you put on HI all teh airblow will go trough the heater matrix, when you start to calibrate a different temperature all starts to be affected by the clogged matrix and where it's blocked.

                      I hope I've been clear enough....

                      YOu can see the airbox and the central main duct and the temp flap on the airbox on this thread:
                      http://www.s2forum.com/forum/showthr...886#post774886

                      here my symptoms and the solution:
                      http://www.s2forum.com/forum/showthr...t=47071&page=2

                      Note that I changed:
                      The two internal temp sensors (believe B5 has only one in the dash with the little fan)
                      The two external sensors the one in the front behind the bumper and the one below the cabin filter (pity to get at it!)

                      But no avail.... It was the heater matrix original part fitted in 2009....

                      Hope this helps

                      Stefano
                      http://www.audisportclub.com/

                      http://www.s2forum.com/forum/vbgoogl...227295&zoom=16

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                      • #12
                        Also the foam can fall off the flaps so they don't work properly.

                        S2 Coupe 3B Project


                        Ur quattro restoration

                        S2 Avant

                        Boost is the new rock and roll!
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                        • #13
                          Originally posted by quattro-nick View Post
                          there is a known heating problem by audi 80 b4 typ and audi a4 that the little heating radiator inside the ventilationbox is getting clogged,no circulation at all
                          You can try flushing it with a garden hose
                          or try a cooling water flushing agent
                          my A4q (in Finland) had problems getting warm in cold weather (-25°C), might be this problem, thx!

                          Originally posted by johne View Post
                          Your internal temperature sensor - the one behind the grill just above the climate control unit - is blocked by dust or the fan behind it that draws the cabin air over it has failed.
                          I'll check this as well

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                          • #14
                            Originally posted by fish View Post
                            ... Unless i go up to HI (30 degrees) then it blasts out heat.
                            It is this statement from Fish that makes me think it isn't a blocked or partially blocked heater matrix. The Hi setting is the only time the Climate Control Unit isn't trying to moderate the temperature so if you can get full heat on the Hi setting the matrix must be able to flow water and provide heat.

                            John

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                            • #15
                              Ripping the center console apart today, i can feel the center axel for the little fan spinning with my finger, i will see if it is fluffed up with dust. Will also check the flapmotors. I dont think it is clogged as i i flushed it with kaustic soda last summer, (its for cleaning drains = disolves most gunk) also, if it was clogged i doubt i would get burning hot heat when on HI. I will let you know what happens. Thanks once again.

                              Kris
                              Audi 80 Competition -94 Daily driver

                              www.garaget.org/fish for more pic´s of my cars

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