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Demister Problem

964rh

964rh

New member
After taking my car out for the first time in cold weather i've noticed that there is no air coming through the windscreen vents.

On a service invoice from before I owned the car a note was put on it saying "Stage one heater error"

Can anyone give any suggestions as to what it could be??

Also, on turning the ignition on after standing for approx. one week, I get a knocking noise through the cabin, it sounds like a pump trying to work empty.

Your help would be greatly appreciated.

Regards

Rob

P.S. - Have been told this week that I treat the car better than the wife. Is this normal for Porsche ownership??:ROFLMAO:
 
directional control for all the vents/demisters/recirc/mixing temps are controlled by 5 small servos under the plastic tray under the bonnet beneath the windscreen.
I know this link below says that you can diy fix a broken servo but if you happen to diagnose a duff one id say buy a new one, you dont want to be doing this job to often as its a bit of a pain unless you are double jointed and 3'2" tall.
Im speaking from experience [;)]
Hint........ you can see the servos moving if you start the car, move the relevant control sliders and get quickly to the servos over the wing

this will/might help you diagnose the fault [;)] http://www.porsche964.co.uk/technical/servos.htm
 
I forgot to add, they are/were approx £50 each from the OPC
I tried DIY fixing it and i ended up doing this 3 times [:mad:] before buying a new one
 
Rob,

Before you go delving around the servos as Elliot has suggested it might be worth a quick 30 sec check on the main blower fuse. It's a 25A fuse in the rear electrical box on the left hand side of the engine compartment. It seems that this fuse has a bit of a habit of blowing and, as a consequence, the main blower will not operate and the air pressure operated "thingy" in the plumbing will stop air being delivered to the cabin.

I've had exactly this problem - I believe Blue also suffered. It's a quick trip to Halfords for a new fuse if that's the problem.

Regards


Dave
 
Thanks for info gents.

Hooked up a twelve volt supply to test and the servo is knackered. OPC Nottingham have on order for me.

Rob

p.s. By the way Elliot, double jointed and 3'2" sounds like the ideal man to some people!![;)]
 
Hi

Picked up servo and still no front window demister.

Tried to move the arm that operates the flap manually and still no air comes through.

Anyone got any suggestions??

Also, in the main fuse box what is relay r41 used for?

Thanks

Rob
 
Rob,

R41 is the DME relay. It's the one that so often causes starting and running problems. It powers the fuel pump and, I believe, has some involvment with the immobilser too.

On the air distribution question I think I've lost the plot over the course of the discussion!!! I think I remember you confirming that the rear blower DOES run so I'm guessing you DO get air - just not to the windscreen. I think Adrian's book delves into the depths of debugging the heating and ventilating system so it may be worth having a look at that.

Regards


Dave
 
Push the white button on the CCU, the LHS one, it should close all vents and push all air for maximum demist to the windscreen.

Then whilst doing this, watch the servos move (lid up obviously) you'll be able to see what servos if any are at fault. Rotate the temp full clock and anti clock to see the heater servos move. Also try looking at the paper tubes that carry hot air from the footwells up to teh demisters/cabin inlets, as these are paper they can rot.
Flapper valves, are these knackered?

Sounds like you need to purchase a book or two to get you started, try Arians book, or borrow a PET ........

Kevin.
 
like Kevin said, check the paper tubes in the footwells for tears
Also register and search http://forums.rennlist.com/ on the 964 and poss 993 for all your questions, you can then post if you cant find your answer in the many searches.
This is where Adrian Streather the 964 guru lives.

 
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