Heater

[rajagger]

I can't get my head around a few things with regard to the heating:

1) What are the 2 slider controls for between the fan and temp control knobs? I haven't got an owners manual - anyone know where i could get one (or a copy of one)?

2) There seems to be hot air coming out of the vents all the time (even when the knob is at cold). I've checked that the control arm on the shut off valve in the engine bay moves and all seems to be ok, unless it needs cleaning inside. That'll be my next job. It'll be ok in winter, but on a warm day it gets pretty hot in there!!!!

3) The fan control knob - settings 0,1,2 & 3 all seeem to be at same speed. 4 is fast. Any ideas whats wrong here? Even at 0 there is air blown into the cabin.

Cheers, Richard

 

[Fen]

The top slider determines how much air is directed to the top of the ventilation system (the screen and face-level vents). The bottom slider does the same for the footwell, the thicker lines indicate more flow. You also have the slider between the centre vents which further subdivides the top ventilation flow between the screen and the face vents.

German cars have heaters that fail to hot rather than cold. The following may only apply if you have auto heater control (numbers on the temp dial rather than the blue/red band).

If your heater is always hot it's most likely a clip that links 2 control rods down the side of the glovebox has snapped and the rods are no longer connected. Take the glove box liner out to check (pull the interior light fuse first or you will blow it by shorting the glovebox light wiring on the dash). The clip is very cheap from an OPC and somebody can probably give you the part number it's such a common failing.

While you're in there take off the tube that runs from the grill on the dash to the cabin temperature sensor fan and clean out the lint on the fan intake, it makes temperature stabilisation much better.

Lastly the fan speed resistor pack can develop a fault. It's never happened to me and I thought the symptom was that the fan would only run on setting 4, but I could be wrong. #4 should be quite noisy so there is no mistaking if it works with lower settings getting progressively quieter. #1 is almost silent but keeps air circulating. Even at position 0 any outside air pressure in the scuttle when the car is moving will push through into the cabin; setting 0 just kills the fan, it doesn't close any flaps. Does the fan do the same on setting 4 as when you push the windscreen demist button? I think the button bypasses some other systems and certainly puts full heat and full fan to the top of the ventilation system, sometimes it helps diagnose what is wrong by its different behaviour.

 

[TTM]

When the resistor fails fans run only on positions 0 (min) and 4 (max).
In my case cleaning the contacts of the resistor proved enough but I guess I have been lucky.

 

[Guest]

ORIGINAL: rajagger

I haven't got an owners manual - anyone know where i could get one (or a copy of one)?

Can photocopy the owners manual for the car below and post it. Email your postal address.
kmarkwaller@aol.com.

 

[richthomas]

TTM is right in that the fans only run in 0 and 4 when the resistor fails. I managed to fix mine by cleaning the contacts too, our cars are even more similar than I thought!

 

[Diver944]

Just as an aside, the fan is supposed to run slowly even when it is set to 0

This ensures a constant flow of air even when the car is stationary.

 

[rajagger]

I checked out my heating problems over the weekend. Fen, your diagnosis about the plastic clip was spot on. It was broken on one side. I have managed to make a temporary repair until I get a replacement clip.

As for the fan speed control - well it seemed to be working ok over the weekend. Either it's an intermittent fault or I have lost the plot!!!![8D]

Thanks for your help.

 

[rajagger]

Keith - thanks loads for the copy of the drivers manual. I had no idea it would be so much work. I owe you a few pints if you are ever in Leeds.

Cheers

Richard

 

[Guest]

You`re welcome Richard...Happy reading!

 

[Mike_Pollock]

Hi
I therory half the total coolsnt, but therre isnt much in the mstrix,and they dont ususlly flood out. Fresh water and a couple of towels should be ok.
Mike

 

[Riverside]

What are the symptoms?

 

[Bobpool]

Either very hot or cold.No in between.

The heater knob click's when I turn it but as said it goes from one extreme to the other.

 

[ChasR]

It could be your vacuum pump which is at fault.

 

[zcacogp]

"The heater knob clicks when I turn it" ... do you have the 'climate control' (i.e. temperature-following) temperature system, or the earlier 'hot or cold' one?


Oli.

 

[Bobpool]

ORIGINAL: zcacogp

"The heater knob clicks when I turn it" ... do you have the 'climate control' (i.e. temperature-following) temperature system, or the earlier 'hot or cold' one?
Oli.

Im not sure.I have a 1986 Lux. Don't have climate control.
I've already changed the heater control valve.

 

[944Turbo]

There is a comprehensive test guide in the workshop manual (available for free download from www.cannell.co.uk/ or promax), but on mine one of the servo motors had seized, it came apart and the motor freed up with a spin on a battery. I guess with an 86 you have the blue red graduated display rather than the temp numbers around the dial. If you have temp numbers around the dial could be the outside air temp sensor.

Tony

 

[Bobpool]

Where would I find the servo motors on my Porsche?

I have the blue red graduated display.

 

[zcacogp]

Bob,

Blue/Red display - that'll not be the 'climate control' model.

The later cars had a heater which would maintain a set cabin temperature within the range of the outside temperature, so it couldn't go colder than the outside air but would monitor the cabin temperature and keep it constant. This is 'climate control' as it controls the climate, but isn't 'climate control' as is commonly understood (on modern cars 'climate control' implies the presence an air conditioning system.)

The 'climate control' 944's had servo motors which controlled the air flaps. If the non-climate-control ones work in the same way then they too will have servo motors. There are some good pictures here:

http://www.clarks-garage.com/shop-manual/hvac-01.htm

The servo motors do have problems - it's interesting that Tony had a problem with his. Earlier on this week I took the fotowell control servo out of my car as it wasn't working, and discovered that it had got wet at sometime previously and was rusted solid. A bit of TLC, a wire brush and some good lubricant and it came apart and went back together again and now works fine ... Wonders of German engineering, eh? []

(Shame the servo said "Made in Japan" on the side ... [])


Oli.

 

[Bobpool]

Thanks for the replies guy's. [8D]

I have no mechanical skill's whatsoever and I unfortunately don't see the servo part's on the link you sent me,sorry[:-]

Can you point me in the right direction of which number they are please.

As punishment I will read my Haynes manul from cover to cover to get a better understanding and to become a bit less of a ' noob ' []

 

[zcacogp]

Bob,

Third photo down, items 2, 3 and 4.

"Defrost flap control motor", "Control motor for temperature mix flap and baffle flap" and "Footwell flap control motor" (which is what failed on mine.)

The haynes manual is not great, or so it is said (I don't have one.) Try reading the rest of the clarks garage site - it will be much more helpful.


Oli.

ETA: Working on the servos is easy. They can be removed with only a few screws (although you will be flapping around in the passenger footwell to get to them), and taken off the car. (The footwell flap one is hidden under a plastic cover but that is easy to remove.) Put +12v across terminals 4 and 5 on the connector (use a car battery charger) and if the little lever on the side moves, the servo is OK. Connect the voltage the other way 'round to make the level move the other way ...