Ant71

Hello all,

Another CCU/ heater conundrum here.
I have search through old threads without avail.

My issue is that the Fan speed is not constant. If I depress the defrost button on the CCU
the blowers don’t come on straight away nor if I just turn the fan speed up, but when I have some revs up the fan will come on but again not a constant speed it will undulate.

The rear blow is working and both front fans. and no problem with heat.

In these fogy, damp and cold day it a bloody nightmare.

So what do we think? The final stage amplifier?

Jamie Summers

I have a very similar problem with mine, but most of the fans seem to have packed up now (having started with exactly the same symptoms as yours). There is still a fan working somewhere, but airflow increases and decreases with engine revs, which rather suggests that it's just the main engine fan moving the air forward.
GT One investigated the problem for me and came to the conclusion it was the CCU itself, though I'm not convinced. They replaced it with a known functioning one, and that seemed to cure the problem, but then replacing the final stage amplifier also cured the problem for about five minutes ! Jaz were also unable to diagnose the problem suggesting that the CCU was not even putting out any codes on the system tester computer, suggesting it wasn't there at all !!!! The CCU clearly has power and the diverter valves and all but one servo seems to be working - annoyingly the one that is stuck points the air onto the windscreen infront of the driver, so I can't see anything with a permanently foggy screen, whilst the passenger side clears fine - typical !!!
I'm really not sure what the solution is. I don't want to write a "blank cheque" to a specialist to diagnose, so have been trying to buy a new CCU on eBay to do some experimentation on my own, but I keep missing them and the Euro and Dollar make buying overseas prohibitively expensive right now. All in all I'm a bit stuck too - you have my sympathy !

Jamie

Ant71

Thanks for your response Jamie, you too have my sympathy.
I think the heater system is the most complicated thing on these cars…to may moving parts. Hope it’s not my CCU. Will have to recheck everything…

If I find a fix I’ll let you know..

Jamie Summers

CCUs are repairable (cost c. £250), or roughly the same price on eBay. Problem is getting a definitive diagnosis that it is the CCU at fault, otherwise it's an expensive experiment !!!!
If I get the demist servo fixed I might just leave it at that for now and just get on with driving the thing !

Jamie

mjshira

Start with checking your rear blower motor, inspect that it is connected correctly. Then check your blower resistor. Then check the front fan blower resistor. If you work through each of these and if they check out then consider a CCU rebuild. This is a complex system and having made the mistake of changing parts I can advise you with some humility ;-) that you don't want to take that approach. The best investment you can make as a 964 owner would be to buy Adrian's book '964 enthusiast companion'

Ant71

Hi thanks for the advice Jamie/Mjshira.

Yes I have Adrian’s book a must I agree, doesn’t really help me with this problem.
I have check the blowers and they all seem to be working OK just not at a constant speed. But I will check through again your right.

Jamie your right too just keep using the thing! Fast with the windows down!

It must be quite funny for the people across the pond. As soon as winter hits the UK the posts about their bloody heaters start.

Thanks for you help again..the story continues

Low 964

Still got it then....good lad

Ant71

Hi Pete,

I was going to call you the other day, fancy meeting up at some point so I can have a look at your flaps!......heater flaps that is.