PDA

View Full Version : Heater speed changes by itself. Weird



ben.yule
22-01-2007, 09:46 PM
I have an issue with my 2000 ( W ) Audi A4 avant.
I have noticed that the heater speed tends to increase by itself.During a short journey I can turn it down 3 or 4 times.
It tends to creap up one bar at a time.
This is very frustrating.
Does anyone know what is causing this.
I did have blocked drain holes in the engine bay & suffered water in the passenger side footwell.Not massive amount but enough.
My worry is that the ecu is now playing up because of it.
I dont have any other issues electrically.
Any help would be appreciated.

JR001
23-01-2007, 12:28 AM
Hiya,
My AC does this when set to AUTO. It is supposed to do this and I think it has something to do with placing less of a load on the battery immediately after start-up. Is yours set on AUTO? Does it do this regardless of setting?

Huweth
23-01-2007, 02:15 AM
Is it Climate control? If so, it is normal on the auto setting and is just trying to get the air in the car to the temperature you have set. Leave it long enough and it will go back to a lower level once the temp is levelled.
If it's not climate control, it could be any number of electronic faults, but you'll have to wait for more replies for help with that!

ben.yule
23-01-2007, 11:30 AM
It is the air conditioning ( climate control)
Im pretty sure the auto button is not on but its still doing it.
I will check it & see.
It does tend to do it more when the engine has not been running very long.

The Sandman
23-01-2007, 12:49 PM
sounds like the AC pressure switch is faulty

VR5_Lee
23-01-2007, 01:43 PM
I used to design Automotive A/C units, not for VW's, but it' all the same...
The theory behind Climatic control goes thus:

Set a temperature (eg. 28 Deg, or whatever that is in old money),
There are two sensors in your cabin;
1. Cabin Temperature - there should be a little grill next to the controls - this works by sucking air across a thermostat.
2. Solar Loading - There should be a shiny half ball (or something) int the middle of your dash somewhere near the windscreen - detects how fierce the sun is.

What happens in the ACC brain? - The cabin temperature will be detected, the amount of sun is taken into account, the flaps within the heater are set to let hot / cold air flow, the fan will blow fast or slow and to which area (feet, face, screen) to acheive the correct result.
Full climatic control realises that Re-Circ gets the car hotter quicker, that feet always lets out the hottest air, and higher air speed will carry it quicker - not rocket science but my passat seems to have forgotten that bit.

So,
- I Recomend you clear out the cabin temperature grill (use an old toothbrush),
- Check you haven't thrown a Sunday Sport on the solar sensor (unlikely to need cleaning),
- Finally, Set the 'target' temperature to the temperature your car is reading outside (theoretically the heater will not need to do anything).

If the fan speed is still going up and down write again - I'll ask a few old colleagues.

Cheers
Lee

ben.yule
23-01-2007, 02:08 PM
Thanks for your reply.
A lot to take in there.
Is what your saying based on the climate control being set to "auto"?
Im pretty sure mine is not turned onto Auto.
Therefore should it not just blow air out at 22degress or whatever I set it to?

Huweth
23-01-2007, 06:41 PM
Im pretty sure mine is not turned onto Auto.
Therefore should it not just blow air out at 22degress or whatever I set it to?

What is being suggested is that you set your temp to whatever is outside as a test. You will have one number for outside, it's low at the moment so should be close to freezing (0 celcius). There is another number for internal temp, that you set to what you want, i.e. 22 celcius.

For the test, set both temps to be the same, and in theory, the fans should stay at a very low level when set to auto. Make sure the demister is not on, as it will make your fans go up towards full speed. The demister button looks like a windscreen shape with arrows going over it. It should not be displayed in the LCD screen.

If the unit is working, during this test the fans should remain low. If the fans go up, you seem to have a problem.

In order for the climate control to settle down and be quiet (low fans), you need to allow plenty of time for the cabin to reach the correct temp. I would guess you need to be in the car for a good 20 minutes in this cold weather before it will stabilise at 22 celcius.

Do the test and report back with your findings...

Dave Avant
23-01-2007, 10:28 PM
Mine creeps up and down too. Its the dual climate version (A4 '03). It isn't on AUTO and is set to ECON. Its starts on one bar, then as the engine warms it increase a few bars, once the cabin is warm it will reduce speed.

Also if I manually turn it up a few bars, when it increases the extra few bars I put on manually will be added to the total when it automatically turns up. I thought it was its own way of controlling and maintaining the interior temp.

My previous cars with climate have just altered the temperature of the air rather than fan speed.

ben.yule
23-01-2007, 10:36 PM
Thanks Dave,
Im glad someone else has experienced the same thing.
I have mine set at "econ" rather than auto.
How do you get it like a good old fashioned blower & to stay on one bar at a certain temperature without going up & down.

Huweth
23-01-2007, 10:39 PM
How do you get it like a good old fashioned blower & to stay on one bar at a certain temperature without going up & down.

Mine is set on econ, demist and floor vents, set to 2/3 bar fans, 20 C. Works a treat...

onzarob
23-01-2007, 10:43 PM
Nice info there V5_Lee. learnt allot:D

On the fan going up and down in speed, I would expect that from a control system. slow when engine cold then higher to fill the cabin with warm air. then slow down when the chosen temperature has been reached. Thats standard control theory ( I did it at college..a while ago;))

The aircon when set to econ as i understand it is only heated and not cooled. so the temp you selected is regulated by hot air and fresh air only. this would i my opinoin be less presice causing the fan to change a little more often.

The only time my car hold a constant fan speed is when i use the front demist function or set the fan speed manually.

Hope that helps.

Rob:D

ben.yule
23-01-2007, 11:00 PM
Thanks for everyones posts.
Appreciate everyones input.

Dave Avant
24-01-2007, 11:11 AM
Don't know. I'll keep on eye on it to see what it does. Just sometimes I've noticed it blowing more and checked to see about 4 bars.

audi_bob
24-01-2007, 12:32 PM
I have twin auto climate in my avant and usually have it set to auto/econ and adjust the temp up or downa nd let the blower do its hting, seems to work for me, tho the extreme back windows get a bit sweaty now and then - to far from the blowers i guess

. is it right with the advise of running the a/c off of econ to keep the system flowing now and then?

Dave Avant
24-01-2007, 01:00 PM
I have twin auto climate in my avant and usually have it set to auto/econ and adjust the temp up or downa nd let the blower do its hting, seems to work for me, tho the extreme back windows get a bit sweaty now and then - to far from the blowers i guess

. is it right with the advise of running the a/c off of econ to keep the system flowing now and then?


Yes it is best to run the aircon every month for about 1/2 an hour, it lubricates the seals and bits. I use it sometimes if its wet weather and the car is steamed up, the aircon dehumidifies the air and clears the windows better. But most of the time I have it on ECON, saves a bit of fuel. :D

audi_bob
24-01-2007, 01:21 PM
cheers Dave. just confirmed my thoughts.
I have had the win climate before in my S4, then changed cars to MERC E55 AMG, BMW Z3m and now back with Audi A6 Avant due to child and dog(s) coming along, and have to say the Audi climate knocks the socks off the other two big german makes. all in, pretty happy.:D

VR5_Lee
24-01-2007, 01:42 PM
Not sure about the Audi - but cars I've worked on in the past have to main settings
- AUTO (Automatic climate control - with air-conditioning - hunting for target temperature)
- ECON (Economy - without air conditioning - hunting for target temperature)
This was from the days of Air conditioning = less fuel economy = £'s

To add to Daves test - set the fan speed to low, ECON off, AUTO off, Temperature Low (a given number not actually 'LO'), Re-CIRC off and no direction defined (if not possible define feet) and the fan should stay stable.
Looking forward to feedback
Lee

>>Posted this without realising there was a 2nd page, Doh!<<

Dave Avant
24-01-2007, 03:06 PM
I think I'll have a proper look to see what its doing.


Another little bug bear with the Audi climate, is the temp setting doesn't go lower than 18 C except going to 'LO', LO is just cool air and 18 can be just a tad too warm, my other cars went down to 16 which was better for me. getting used to it now.

MalcQV
25-01-2007, 10:05 AM
Excellent info thanks.
I have noticed on my Passat, you can push the ECON/AUTO button and neither is displayed. So it is not on AUTO or ECON? Is this normal if so what does it mean?

Dave Avant
25-01-2007, 11:16 AM
Right, tested it last night;

Engine cold from being sat at work all day, settings are windscreen (up arrow), feet (down arrow), ECON on, AUTO off, set at 18 degrees both sides.

Start engine, 1 bar after a few minutes of driving it creeps up to 3 bars, then upto 6 bars, stays like this for about 10-15mins, when it gets warm in the cabin, it drops back down to 3 bars and stays there, whether it would go lower on a longer journey, I'm not sure.

Just as a little test to conclude the fan increases/decreases to maintain the temp, after a 1/2 hr journey it was on 3 bars, opened the windows to let the cold in and hey presto its back upto 5 or 6 six bars, close the windows and after a few minutes its back down to 3 bars. :D

So its normal and not wierd. :beerchug:

ben.yule
30-01-2007, 09:18 PM
Nice one Dave.
Just got back from holiday & was going to investigate but now I have no need.
Nice touch.:D