blowing in hot air even set on cold
 

I have a 2001 1.8 Sport with manual air con and heating, not climate control. It does not happen all the time but sometimes when I start the blowers and have the vents open to blow to face setting, it blows hot air in either with the air con switched on or not. If I then turn off the ignition for a while and then restart it then blows cold air in, and ice cold with the aircon switched on very confused as the aircon is ice cold. Please help someone as I have no idea what to do, this is my second S40 and this never happened with the last one.

Blowing in hot air even set on cold
 

I have found the problem myself I took the stereo out and then changed the heat setting from hot to cold and it worked fine. On inspection at the back of the stereo housing I could see the arm moving changing the setting. I then found that if the setero cables are not held out of the way, when putting the stereo back in they can get in the way of this arm causing it to get trapped and stick. I hope tihis helps anyone who is having the same problem.

Strange as my wife was complaining of the same thing on her car last night:lightbulb:

blowing in hot air even set on cold
 

Well the problem is back again so I dont think its the stereo cables, However if I give the top of the dash a light bang it will change from what the heat setting is stuck on. Very strange I know I need to replace my resistor pack but any help would be great

are you experiancing a clicking sound coming from behind the dashboard, which would indicate the cog on the hot and cold control is slipping

hmmm sounds to me like you were in the right place to start with, it sounds like the arms from your heater controls are loose and not opening/closing the heater matrix valve properly.

2 things i would do is -

1 putting the heater control knob over to hot flush the matrix out with a hose just incase crap is stopping it closing.

2 check all the arms ect are not loose in the ventilation housing wich is behind the pasenger side of the dash and behind the center part of the dash.

failing that just keep bashing the dash ;)

blowing in hot air even set on cold
 

There is no clicking noise that i can hear. Thanks for the advice I am dreading taking the dash apart so will check what I can get too. I think the whacking the top of the dash on the passenger side will have to do until it stops working. Then pay out loads to find the problem.

I've just brought a V40 and it also has the manual air con. It seems have the same problem in that it is usually stuck on hot but occasionally it comes through cold. I've not tried hitting the dash.

Hobbo did you resolve it? Does any one else have any ideas? I've ordered a maintenance manual so won't start trying to fault find until this arrives.

Hi all,

I've been battling with this on my 2001 Y reg V40.

I've got the manual control unit and the problem was very similar.

The car would give out the air temperature that which the knob was set to when the car was switched on. Then wouldn't alter.

I tied it down the control unit. So I took it out of the dash and into pieces.

It turned out to be the potentiometer that the knob went into on the circuit board.

I haven't yet found a replacement.

The result was that if I wiggled the knob when in the temp position I wanted, it would alter, leaving me to think the pot had just got it's tracks worn out.

The part is a 5K ohm Piher vertical trimmer potentiometer.

I've had the change the control unit and it's gone away.

But if you can find the Piher parts, I'd be interested to repair my old one!

Many Thanks,

Daniel.

Potentiometer is not such exotic part to get. Every local electronic store should have it - or order it, if it is not on their stock.
It is just regular 5 K , vertical, size PT15 with big hole for axle. But you will have to bend the center or both lower pins. Compare boh old and new one, and you will see why.
Another thing that must be done is the adjustment of axle. Because potentiometers come with 20% tolerance in resistance, and not two are the same. Climate units are built so that are soldered first and programmed later. That means the each program (firmware) is also set for potentiometer specific tolerance. And if you change potentiometer with another one, you may have a little error in position. You won't feel that error in temperature knob (unless you measurre the exact temperature, which is pointless for +/- 1 °C); but you can see it with fan speed knob.
I changed both potentiometers on my automatic climate module. Of course, new potentiometer had different tolerance as original. Result was, fan was turning on position 0, but it stopped somewhere between AUT and 0. So what I did - took the fire lighter and heat up knob axle, then twist it just a little bit and try it again. After 3 tries, I got it all set. Well, there is still non-linearity in speeds (it misses 3,5 and don't reach full 5, but 4,5 only), but I don't care that much. As long as AUT and 0 works fine.

Sorry for lond writing, but you get the idea.