StevenB
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| posted on 2/2/12 at 11:57 PM |
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A4 Heater problem
Guys,
Can anyone shed some light?
As the temp on the gauge builds to 90 deg
you can gradually feel the fan air temp
coming into the car getting hotter.
When it gets to 90 it sits perfectly on temp
never over heats etc.
But the air coming through the dash is practically
cold - especially on the passenger side.
To get any sort of heat you need to close all the vents
bar the drivers side and slow the fan speed to 1.
Its been like this for a few weeks and the car was just serviced
with a new water pump / timing etc and it has not cured it.
So its not the water pump.
2005 A4 Avant.
The garage said it might have to start ripping stuff out to
source the problem.
Any suggestions?
S
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PSpirine
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| posted on 3/2/12 at 12:14 AM |
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Several things spring to mind:
1) When the car reaches 90 deg it opens the thermostat and you end up cooling the entire circuit to a manageable temp. Whilst it's building the
heater is the only thing that's cooling the engine. However, with a fully functioning system you should still have a stable temp.
2) Audi gauges are weighted to around +/- 15 deg around 90. That means that anything from 75 degrees to 105 will show up as 90 on your dash.
3) Combined with the above, you may have a dodgy thermostat but not realise it due to the dash weighting. If you've got a dodgy thermostat that
doesn't close properly you'll be running cooler..
Ideally you need a Vag-COM to check the real temp of your engine. VAG use two sensors in the cooling circuit (one for the ECU, and another for the
dashpod and diagnostics/climate control - god knows why since it means you never know what temperature the ECU is sensing). You'll end up with
strange things if only one of those sensors has gone wobbly.
4) You may have an airlock in the heater matrix?
Just thoughts off the top of my head.. my TT does a very similar thing although it's not quite "cold", but I'm pretty sure
i've got a dodgy thermostat as mine struggles to get to 90 degrees (as displayed on dash), despite a recent thermostat change..
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norfolkluego
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| posted on 3/2/12 at 12:29 AM |
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Had a similar problem in an MR2 I owned, turned out to be low coolant level, easy thing to check/rule out
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blakep82
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| posted on 3/2/12 at 12:36 AM |
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low coolant level, and also, there's now usually an electronic temperature valve thing (that opens and closes when you tune the dial/press the
up down button for temperature) could be broken/sticking/breaking
could be a suspenct
________________________
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don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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StevenB
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| posted on 3/2/12 at 12:37 AM |
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A mechanic I know said the only time he heard
of this warming then cooling was when the water pump
had a plastic impeller failure where it would slip on the
spindle but only after the temp had warmed it sufficiently
so it expanded.
I mentioned this to the garage prior to the service but
as the water pump was being changed anyway this was
going to be discounted as a cause. Unless it still is and they
didnt change my old one during the timing service.?!?!
The garage checked the computers and said all was OK.
S
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simonwinn
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| posted on 3/2/12 at 08:48 AM |
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Its a common problem on the A4, there is loads of info over on the VWAUDI forum.
There are four servo controlled flaps behind the dash that control the heat and direction of the air flow and these are prone to failing, either
sticking or giving up completely. If I remember 3 of them are located behind the glovebox and can be found by looking for the colour coded arms, red,
green, yellow, and blue, I think. The last one is in a similar position on the drivers side.
Take the glovebox out and work the heater through all the air positions and hot or cold and see which one doesn't move.
There is a guide somewhere about cleaning the internal contacts, its worth a try as new units are very expensive.
Hope this helps..
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owelly
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| posted on 3/2/12 at 09:41 AM |
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Just had the same problem with my A4.
Open glove box and remove the screws holding it in. Remove the entire glove box assembly to reveal a plethora of electric flap actuators. Operate the
heater controls to see which one is stuck. Remove, gently push in the tabs to remove the cover. Clean motor with isopropanol cleaner (or similar
cleaning stuff). Replace and congratulate yourself on saving a bloody fortune. You may need to do more than one servo as each one won't move
until the corresponding one has reached a certain point which makes you think its bust. If that makes any sense?
http://www.ppcmag.co.uk
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tegwin
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| posted on 3/2/12 at 10:45 AM |
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Seems to be a VAG thing... my polo suffers from sticky servos on the aircon system.... sadly I cant get to the recirc valve as its burried deep within
the dasboard :-( ... I didnt want fresh air anyway!
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www.verticalhorizonsmedia.tv
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StevenB
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| posted on 3/2/12 at 10:39 PM |
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a couple of months ago there was a bit of clicking coming from behind the dash
but it stopped and I never thought much more about it.
The air flow is really strong and it does move in accordance
with the directional settings - screen - feet etc.
I will have a go at the glove box.
Thanks for all the suggestions.
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