Heater Blower

Dave Wilkinson · Oct 28, 2009

ORIGINAL: dirtgod

OK chaps hey presto i now have heating but how do i get the thing to blow cold air its a non air con cheers

If you turn the temperature selector to the blue dot the CCU SHOULD close the hot air entry into the mixing chamber, leaving just the cold air to flow into the cabin. However, my emphasis on "SHOULD" is no mistake. The servo motors are known to suffer problems such that they will not operate the flaps as expected.

The other common problem is that the flexible tubes connecting the sill tubes to the mixing chamber disintegrate and allow hot air to escape into the footwell. No amount of fiddling with the CCU controls will have any effect on this problem. Replacment of the tubes (approx £10 each at OPC) is the only solution.

Regards

Dave

robwright · Oct 28, 2009

Dave. Dirtgod is the guy I have been posting om behalf of. Basicly as I already posted we now have control of heat. I.e it is easily turn off and onable and moves into the cabin but only by means of the rear blower. However when max cold and blower 4 is selected there is no movement of air into to the cabin. As I said this leads me to suspect the blower driver under the fusebox. As it happens I have just bid on the one you linked to on ebay. It's only a fiver and can always be sold on if not the solution lol.

l.chadburn · Oct 28, 2009

Hi rob

We must be on the same wave length, I bid the 5 pound. LOL

happy bidding and good luck.

If you win and don't need it please let me know and like wise i'll do the same

regards lee

robwright · Oct 28, 2009

Well mate that depends on how much the guy I am biding for it for is willing to pay lol. No hard feelings either way eh. I thought the HVAC setup in my 944 was complicated. This is however my first experience of cars without any water and an engine that is......welll I won't say in the wrong place as they have been doing it for years and they still are so they must be doing something right. Besides with a big lump of gearbox in the back my 944 turbo can be almost as much of a handful as a 911 at times. Especially when the boost arrives unexpectedly at the wrong moment!!!

l.chadburn · Oct 29, 2009

Just ordered a new NTC sensor which should come hopefully next week with the postal strike on.
Hopefully that should stop the rear blower blowing constantly at high speed.
Will let you know, otherwise I will be picking ya brains again.

fingers crossed

lee

colin129 · Oct 29, 2009

ORIGINAL: robwright

This is however my first experience of cars without any water and an engine that is......welll I won't say in the wrong place as they have been doing it for years and they still are so they must be doing something right.

The man is softening...its only a matter of time now...[

]

robwright · Oct 29, 2009

The man is softening...its only a matter of time now...[

]
[/quote]

Well I'm not ready to give up on my 944 just yet. I think it is by far the best car I have ever owned!! Actually don't think I will ever give her up. Maybe in the future I will be looking to increase my portfolio. If that was the case then I would defo consider the 964. I have had a go in my mates and although it is a completely different animal to my 944 turbo it is not without it's charms and appeal. I do keep reminding him though that technically mine is faster albeit that he doesn't have to have a tea break though while he is waiting for the boost to arrive [

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Steve Brookes · Oct 29, 2009

ORIGINAL: robwright

Well I'm not ready to give up on my 944 just yet. I think it is by far the best car I have ever owned!! Actually don't think I will ever give her up. Maybe in the future I will be looking to increase my portfolio. If that was the case then I would defo consider the 964. I have had a go in my mates and although it is a completely different animal to my 944 turbo it is not without it's charms and appeal. I do keep reminding him though that technically mine is faster albeit that he doesn't have to have a tea break though while he is waiting for the boost to arrive []

Sounds a great idea to have both. Exactly what I did albeit that the 964 followed a boxster that remains as a faithful companion in the stable [

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NeilW · Oct 30, 2009

ORIGINAL: l.chadburn

Just ordered a new NTC sensor which should come hopefully next week with the postal strike on.
Hopefully that should stop the rear blower blowing constantly at high speed.
Will let you know, otherwise I will be picking ya brains again.

fingers crossed

lee

The good news is that this has to be the single easiest part to replace on a 964!

Dave Wilkinson · Nov 1, 2009

Considering the amount of interest this topic has received I've added a PDF document to the 964uk.com web site deailing the operation of the 964 heating and a/c system including some suggested diagnostics. The page can be found here and you will need Adobe Reader in order to access the page.

Please pass on any comments - both good and bad - as the coverage of the subject can be modified as necessary but it seems a worthwhile subject since it does seem to cause so many problems.

Regards

Dave

Steve Brookes · Nov 1, 2009

This has become a timely and pertinent thread for me too because I have now been able to make a partial diagnosis that shows there is a fault in my own HVAC system. This is not only blowing a main fuse (#1 in the front compartment) but is causing such a big current drain that it's causing starting problems with my car....some of you at Curborough on Saturday will know about this [

].

I'm on the case of trying to track it down and luckily Dave is helping me with it [

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appletonn · Nov 1, 2009

Great document Dave, though hopefully will never have to refer to it again![

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l.chadburn · Nov 11, 2009

Help again please

I got my NTC sensor and front regulator today, changed them, but still the front and rear blowers blow on full even when the ignition is switched off.
I also tried changing the relay in the compartment in the engine bay - no change.

Although I also found that I have a relay missing, its the one next to the blower relay in the rear compartment.
Does anyone know what this does and if I definately should have one?

If you don't know which I mean - there is a picture of it on Steve Brookes post on 'My tale of the HAvC system causing starting problems'

or any other suggestions before I look at replacing the CCU

cheers lee

Dave Wilkinson · Nov 11, 2009

Lee,

The only other relay in the rear panel is for the heated rear window.

I have to say that with both cabin blowers AND rear blower running with the ignition off it sounds very much like your CCU has gone berserk. The NTC sensor ONLY controls the rear blower - not the cabin blowers - so the CCU is the only common point I'm afraid. I can't think of any alternative.

Regards

Dave

Steve Brookes · Nov 11, 2009

According to Adrian Streather's 964 manual the two causes for the blower running all the time with the ignition off is a failed NTC sensor (which you've changed) or a broken engine fan belt. Is your belt (and the belt sensor wheel) OK?

l.chadburn · Nov 12, 2009

Hi steve
Yeah I have that book.
This was going to be my next question. I have no air con so i only have 2 belts, which are both in tact, however my fan belt warning light is on on the clock.
Am I being completly thick and have missed another belt or would it be the sensor that has gone.
lee

Dave Wilkinson · Nov 12, 2009

If the belt warning light is on I'd guess there's more than a good chance that the CCU THINKS the belt has broken, even if it hasn't. Under these circumstances it's probably not surprising that the blower is running as the CCU will use it in an attempt to keep the engine cool. I'm not sure if that would explain why the cabin fans are running though.

The belt sensor is a small microswitch operated via a wheel which runs against the belt. The sensors are known to fail - sometimes the wheel bearing seizes and makes a noise - or just move out of adjustment. Replacements are not expensive.

Regards

Dave

Steve Brookes · Nov 12, 2009

I agree with what Dave has said. The fan belt wheel sensor tells the system the state of the belt. So if the sensor is duff even though your belt is OK it's giving a false message. Checking/changing it would be a good start (you need to do this anyway to stop the light on the dash). Fingers crossed that it will solve your blower problem.

l.chadburn · Nov 12, 2009

Cheers guys for your help and advice.
I will look at this over the weekend and if necessary order a new fan belt sensor.
Like you say, hopefully this will stop the rear blower.

Cheers again
Lee

iangray100 · Nov 12, 2009

Dave , you say in your doc that there are UK places that will fix CCU's...who as all the ones I know are offshore ?

Its not that I have an issue today ( as I fixed my one for with a16p transistor ages ago ) but for others and my records ?