Heater Problem, Advice Sought

[Loopy]

Hi All,

My car heater will only produce hot air (Think of renaming it Tony....) which is all well and good in the winter but less desirable in our marvellous globally-warmed summers; does anyone have any idea what would be the most likely cause of this?

The temp. control knob rotates freely enough through its entire range; it is of the type where the degrees can be set and the blower has an 'Auto' position.

The little sensor up in the overhead panel seems to run freely (if a little noisily).

I'm hoping that someone has had similar problems and was able to remedy the fault. There doesn't seem to be any difference however slight regardless of the chosen temperature.

Incidentally, if it makes a difference to how it is to be resolved, the car does not have aircon.

Any help or advice gratefully received....

Thanks

Loopy

[archman1]

Hi Loopy

There is a chance it could be the flap motor. I've not had a problem with mine but others have.
I found this PDF file which shows the problem....
http://storgatan.info/xm/teknik/XMspjallmotorbyte.pdf



Cheers
Steve

[combwork]

Hi Loopy,

Have you taken the temperature sensor off? Might be worth checking the 4 pin plug/socket and cleaning out any fluff. If air's not going through the sensor it might `think' the cabin is colder than it is....................... Jim.

[Loopy]

Thanks Steve;

The square end of the flap motor IS sheared off; thanks for the info there, I thought that was responsible for air distribution through the various vents; does it also mix the cold air from outside with the heated air from the matrix box?

Cheers

Loopy

PS: Thanks Combwork, I'll try cleaning the sensor up tomorrow in daylight-failing that I'll post and see if anyone has stripped the motors & sensor from a scrapper recently..

Loopy

This post has been edited by Loopy on March 10, 2007 11:04 pm

[Peter.N.]

Hi Loopy

Yes, failure of the flap motor is a fairly common problem, I have had it happen twice, but its usually the motor itself that packs up or becomes sluggish. On the VSX the only motor is the one that controls the hot/cold mix, the other functions are controlled by cable operated flaps.

Peter.N.

[Loopy]

Hi Peter,

The flap motor is not serviceable as although the motor is working the squared end is sheared off, so I'm looking for a good replacement.

The sensor is spinning but grumbles a bit and I'm going to give it a clean-out and a touch of graphite to lubricate it; if I can get one I'll replace that too.

You mentioned the VSX is cable-controlled apart from the hot/cold mixture, VSX is series 2 I think, and my car is S1. I Don't know how similar the heaters are between the two types of dash. The spindle that is motor driven on my car has a cable guide and looks like it could be operated by a cable on different versions of the car; if push comes to shove and a suitable flap motor is not obtainable I'm thinking of fitting a short cable with the knob in the glovebox; at least I'll be able to adjust the routing of the air that way without having a spurious fitting visible on the dash, and when a flap motor turns up I'll return to that.

My main problem is the actual temperature of the air; it's pleasantly hot at the mo but would be quite stifling once the weather improves.....

Do you know how the air temperature is adjusted? Is there a heater valve that opens and closes allowing water through the matrix, and if so is that motor-driven or cable?

My car is non-aircon but auto heater, ie, it has temperature in degrees marked on the knob. The knob turns thru' its range with a series of clicks but doesn't seem to have anything attached to it- there's no feeling of drag like there is with a cable....
Again, if I'm not able to sort the problem definatively I'll look at fixing a temporary cable in an unobtrusive manner as a means of adjusting the air temp while I try and source the correct bits...I just need to suss out how the temperature is controlled on my car (Series 1 Si) and take it frim there...

Cheers

Loopy

[Peter.N.]

Hi Loopy

After made the last post, I read your signature and realised that yours was a Mk1 but then I also realised that I had only had that problem myself on the Mk1s! I dont know whether they have improved the motor on the Mk2 or if its just because they are newer, but I think the motor is the same. I remember mine went while I was on holiday, so I had to remove the glovebox and the motor so I could manually reset the flap, and then replace the motor to hold it in position.

The 'modus operandi' is this: The sensor in the roof sends a signal to the control unit (behind the controls) informing it of the temperature in the car, the controller then compares this with the setting of your temperatur control, if the setting is higher, it drives the motor to increase the hot air input, and if lower the cold - you get the picture. As the temperature in the car increases or decreases the sensor causes the control unit to make the neccessary adjust to maintain it at the setting that you have selected. Clever isn't it? Its a sort of feedback loop, I think they call it a 'servo circuit' and the motor is the 'servo motor'.

You should be able to obtain a replacement from your local scrappy or if you dont have one try ebay, if no one on the forum has one. I would suggest that you try and get one from a Mk2 if possible as in my personal experience they seem to be more reliable.

Peter.N.