Heating. No hot air in LH footwell

johnedwards · Feb 5, 2010

Hi.
Long time since I posted so a Very happy and prosperous 2010 to all.
I have a problem which has just made itself evident. I don't often use the car in the Winter so the heating system is not often in use. However, after a trip on Tuesday to watch a stage of the Classic Monte, I am suddenly finding that I cannot get any hot or warm air to the drivers footwell. LHD. Cold I have plenty but no control over the heating. The right hand footwell is fine.
All was well on one recent trip and then on the last it was not.
I have had a lot of work done on the car recently, including the door check strap, which entailed the removal of the LH door, also the replacement of the A/Con evaporator, which seemed to entail the removal of just about everything within reach. It's possible something was not quite connected up properly.
Anybody any idea's please.
Thanks in advance.
John.
Car. 1997 Carrera S.

zwhitea · Feb 5, 2010

You will either find that the motorised flap in the footwell has failed or not connected electrically.?

You can see it inline in the attached photo... Black plastic unit above the alarm module. I have had to replace most of these over the last few years...

*always buy new from an OPC.. not too expensive..

Adam.

clyde · Feb 6, 2010

ORIGINAL: zwhitea

*always buy new from an OPC.. not too expensive..

Adam.

Depends on your definition of expensive I suppose - £150 for a little 12 volt motor, a variable resistor and a bit of plastic seems quite expensive to me [8|]

I got a used unit on fleabay a while back when mine went and it's still going strong [

]

johnedwards · Feb 6, 2010

Hi thankyou all
Zwhitea. Is it the black piece in the air ducting. This was all disturbed when the door was taken off recently to repair the door strap.
Clyde. Thanks if it proves to be that it is broken and not just not connected properly after the disturbance, I will try ebay.
Maurice. Is the part you are referring to the same piece as Zwhitea refers to.

sidned · Feb 6, 2010

Is this the same for the side vents? I'm getting very little airflow through either side vent, but loads through the central ones. Is there a similar module attached to each side or is there one that operates both side vents?

zwhitea · Feb 6, 2010

Is it the black piece in the air ducting

Yep.. you will find this has a servo system attached to it. The 993 has few of these making up the heating system.. Same servo design with different levers/attachments etc..
I had to replace this one (actualy drivers side in my case) last year.. OPC part was just over £100 delivered after discounts...

I have tried secondhand parts before.. had to replace 3 of these servos so far... the first 2 I used secondhand parts from well known breakers, at ~£50 each.. but one failed after 6 months which is when I decided to go new... As at best secondhand these things are over 10 years old..

You maybe luckey and a secondahnd one will hold up... (one of mine is - the re-circulation servo).. all depend on the price you want to pay, and the risk.. a breakers will only normally give you 30 day warrenty on electrical items... ebay..none at all.

regards adam.

johnedwards · Feb 7, 2010

I have dismounted the LH servo, left it wired in and can see that it does not function. The next thing is I removed the RH and checked the operation. It only worked when the heat control knob is turned off cold. It would not shut down again when I move the slider, which I would have thought controlled the volume of air. In other words the slider has no affect at all.
I then plugged in the RH unit on the left side just to prove the point and it worked. But still no control with the slider. I appreciate it could be that a thermostat could be involved in the gradual closure and it will not work until the motor is hot. Can anyone confirm this please.
Thanks again.
John.

johnedwards · Feb 8, 2010

Further to yesterdays post, I forgot to mention that I found a large paper towel in the ducting on the RH side. I am wondering if the lack of the slider for the volume control being able to close the vent gradually prompted someone to try a bodge to reduce the volume of air.
Any comments on my previous post about the slider not closing the vent would be appreciated.
Thanks again to all who have responded so far.
John.

clyde · Feb 8, 2010

I presume you mean the slide controllers for the windscreen and footwell air John? If so, these do not control the motorised shutters in the footwell cills. These control more motorised valves at the top of the heater unit within the front luggage compartment. You need an assistant to work the levers while you peer in the front (after removing the plastic cover) to check if these are working, unless of course you have extra long arms [

]

I'm not sure that the shutters in the footwell cills do anything but open or shut fully. As a temporary fix you can of course push the flap open and re-connect the hose, at least that way you will get hot air into the cabin. Fine when it's always cold but gets a bit of a bu99er in the spring when it's sometimes hot and sometimes cold. [8|]

The paper towel's a bit of an odd one....

johnedwards · Feb 9, 2010

Thanks Clyde.
That put my mind at rest. I was beginning to think that there was something wrong in the central control unit.
I will try what you suggest.
At the moment I am waiting for my brother to get a price on the servo motor from a local factor in the UK. The only way here is to go to an OPC. As it's a Hella item, I hope to be able to do this in the same way as I saved over £400 on the evaporator and other AC parts recently replaced.
Regards.
John.

Porker993 · Feb 9, 2010

ORIGINAL: clyde

These control more motorised valves at the top of the heater unit within the front luggage compartment.

I agree. The control unit sliders control motorised valves on top of the heater unit. One for each side, driver and passenger. One of these failed in my 964 - same design as 993. The default position is closed (cold air) so that could explain your problem. My 964 one (LHD) failed because oil from the aircon system was leaking into it. It worked fine after a quick cleanup. I suspect yours are the same - a faulty contact which needs a quick cleanup should sort it out. They are easy enough to get at - just remove the plastic cover at the rear of the luggage compartment.

johnedwards · Feb 12, 2010

Thanks Porker 993
In fact after I found out the other day that I could not buy this item, made by Hella, because Porsche has probably paid for the tooling and it is therefore only available through them. So I decided to dismantle the unit and check it. If all else fails...
I found that I could turn the motor shaft and when I applied current direct to the terminals it turned readily in both directions. Reassembled and tested it seems to work well. At the moment solved for no cost. It is usually warm down here and the heating is not often used. This could mean that the motor had stuck in the closed position. I will make a point of switching on the heating each time I use the car in future.
I have also recently suffered a leaking evaporator, which has just been changed, so I will check the mixing flaps. Is it really easy to get at them. They are not hidden under the evaporator I hope.
In my experience nothing is ever easy to get at. First car I have had to take off a cam cover to remove a spark plug!! Front RH side if anyones tried it. Even my old garage ( Porsche specialist) in the UK admitted to doing it that way. But not necessary on all 993's??
Thanks to all posters again.
Regards.
John.

Porker993 · Feb 12, 2010

Damp and lack of use probably meant the contacts were not great. Now you have freed it off, I am sure that will be fine, as long as you keep using it as you say.

clyde · Feb 12, 2010

That'sthe kind of fix that I like John.

When I took mine apart I found that the contacts were actually burnt out, Presumably the motor jammed and the resulting constant flow of electricty worked like a mig welder on the thin copper of the contacts [8|]