944 Heater

[dawn lang]

As we are all probably aware it has been bloody cold, and for some reason I have had no luck in extracting any heat from my 85 oval dash 944.

I have owned the car for about 14 months, and it has never worked. The car is a third car (although I am looking to use it as my main), so it has never really mattered as I wasn't using it during wet and cold weather.

I have tried a couple of things.
1. Replace the dash mounted heater controls - No luck.
2. Checked the blower unit and flaps on the bulkhead pannel under the bonnet - All free - No luck
3. Definitely getting a circulation of water through the engine (and hence I hope the heater matrix).

I have refered to the unhelpful Haynes (bloody American thing) manual, with no luck. Where now? What have I missed and where the hell is it located if I have???

Ta

 

[Guest]

Hi dawn,
I had a heater problem to, it only went hot when the temp knob was turned full to 30. It turned out to be the outside climate sensor, thats next to the fan grille on the drivers side under the bulkhead (2 inch black probe with a loom attached to it). Try pressing the air circulation button first to stop fresh air comming in, if the heater control then works, then it's the outside climate sensor. It's £18+vat from Porsche. If you have the air circulation button on all the time, your windows will stean up. Hope that helps.

 

[944Turbo]

I think the 85 cars do not have the temp sensors (does it have the blue / red indication? ( no sensors) or numbers? (Sensors) on the heat control?)
On my 86 car one of the heater servo motors had seized, I dismantled it, ran the motor out of the box and reasembled it it worked fine after that, most likely it is the one beside the glovebox.
Until the servo motor worked the vacuum heater valve under the bonnet didn't open.

Tony

 

[Diver944]

As Tony mentioned the glovebox, I'll say it is a good idea to take the glovebox liner out (5 screws) and you can then see the heater control flaps to the right. You should be able to see them moving as you turn the dial from red to blue. If they don't move it could be one of the motors as Tony described or the control unit itself in the dash behind the red/blue knob.

Other things to check are the tiny black vacuum pipes in the engine bay, are they all connected ok and have no splits anywhere?

Just had a silly thought. Is their a seperate fuse for the heater listed on the inside cover of the fusebox.

 

[dawn lang]

Thanks for the advice. 944Turbo, the heater control pannel went from blue to red (or to be more precise the original went from white to white!!), so that rules out the temp sender.

I shall give the control flap motor a go this week. I have checked the vac hoses once, but I figure it may be worth another check.

If anyone else has any other ideas no matter how off the wall, please let me know, I just need heat!!

 

[944Turbo]

There is a way to check the motors are working - bypassing the heater controllers - I will try and dig out the relevant section of the manual later today,
Tony

 

[944Turbo]

The socket on the servo motor looks like this (well a bit)
_____________
o - o (a)

o o o (b)
_____________

The small o's are the contacts.

The manual says apply 12V across (b)+ and (a)-ve to close the motor - it doesn't say but I am sure I reversed this to get it to move the other way. However it didn't move on mine until I had removed the motor from within the unit (easy but lots of small bits) and run it connected directly to a battery.

Hope that helps,

Tony

 

[Riverside]

There's a comprehensive fault diagnostic procedure given in section 87 of the 944 workshop manual (vol3 - chassis). You'll need a multimeter []

 

[Diver944]

There is also a large section in the Garage Shop Manual at http://www.clarks-garage.com/

It's under H for Heater Malfunctions (note that it's written for LHD cars some some bits are reversed)

 

[Guest]

Thanks for the suggestions i will see what i can find[]

 

[Guest]

Not much luck so far, the guide in the manual is for Air conditioning, should have mentioned that I don't have A/C, and there's nothing in the Garage shop manual that helps with this particular problem, but it looks to be a handy site anyway![]

 

[Guest]

Seems to be the output from the heater control panel, just switches the solenoid vacuum on or off, i am not sure if there is anything else which could affect the output from the heater control panel? Does a non a/c car have the internal temp sensor & if so could this affect the heater control panel? Just some thoughts to ponder on.

Neil

 

[Diver944]

ORIGINAL: cropps0

Does a non a/c car have the internal temp sensor & if so could this affect the heater control panel?

If your car has the automatic temperature control system but not A/C, then yes it has three temperature sensors that help the system maintain whatever temperature you dial in on the knob. They are located:

1. In the passenger footwell at the end of the flexi pipe that connects from the grille by the cigarette lighter
2. Behind the central vents in the centre of the dashboard
3. Under the plastic plenum at the back of the engine bay near the wiper motor.

No. 3 failed on mine a few years ago and was under £20 from an OPC

IIRC No1 senses the temperature in the cabin. No.2 senses the heat given out be the heater. No 3 senses the outside temperature as it is drawn in through the grille under that plastic plenum

 

[Guest]

I don't think it has the auto temp. control, as the temp dial is just a red/blue gradient & not temp. marked, but i will have a look anyway, just in case. Thanks Neil

 

[homesea]

Hello,
I think its down to a little white clip behind the dashboard that holds all the heater controls togather. I am sure someone will be along soon with the part number [8|]

 

[pauljmcnulty]

see here:

http://www.porscheclubgbforum.com/tm.asp?m=305934

Very easy to do, got mine from Chris at Exeter PC. Do remove the fuse for the glovebox light, though, you WILL blow it! []