964 blowers always on?

Patronus · 04-30-2012, 01:29 PM

I just bought myself a 1991 964 like I had some years ago but the ventilation fans on this one are always on when the ignition is on, even if fan speed zero is selected on the CCU. I'm talking about the two blowers in front of the dash, not the rear heater blower.
I searched the topic and I saw at least one person saying that they should always be blowing, and that there is no difference between zero and one on the 964 CCU. My previous car must have had perfectly silent and balanced blower fans because I really can't remember ever hearing/feeling the fan unless I activated it. Also, on this car the stream of air is quite strong at zero. If you hold your hands in front of the vents you can clearly feel the blowers working. If you go past 1.5 it becomes faster and after 3 it becomes violent. So, clearly the reostat is working.
My question is this: Can someone please verify what the situation is with these blowers, namely if they are indeed always working when ignition is on; if so, should the fans be audible (very audible in fact) at zero. With the car not idling of course!

964TargaC2 · 04-30-2012, 08:56 PM

See this thread and the links therein\

964 Climate Control Troubleshooting

Patronus · 07:46 AM

Thanks 964TargaC2 but I have studied those links and I couldn't find the answer there, hence my question here.

Presumably you drive a 964. Can you please tell me if your car's dash blowers are always on when ignition is on, even when you selected zero speed on the CCU?

964TargaC2 · 05-01-2012, 10:09 AM

No, the dash blowers come on when I use the knob, they do not come on with the ignition alone although the CCU blower (on the back of the unit ) runs on sometimes..

Patronus · 05-01-2012, 01:56 PM

Thanks 964TargaC2, that strengthens my suspicion that there may be something wrong with my car's final stage amplifier which controls the speed of these blowers.

Any other 964 owners/subject experts out there that may shed some light here?

The little fan behind the CCU is designed to run for about 15 minutes after the car is switched off, and that works fine in my car.

Merle · 05-01-2012, 02:51 PM

It seems my fans are always blowing slightly as well when the car is running. Does the engine fan have anything to do with the AC system? The fan that spins with the engine/alternator is the fan I'm referring to.

Patronus · 05-02-2012, 09:14 AM

Merle, the engine fan only blows air when the heater is in use. The A/C gets its air from outside.

rbogh901 · 05-02-2012, 04:54 PM

It seems like that is not an uncommon problem. My car does not have it. My buddy's car is doing it now though. It would bug me too.

Merle · 05-02-2012, 06:59 PM

I wonder if this has anything to do with different years or ccu part numbers then? I've heard of this with lots if people's cars and have also heard it is only part of the earlier 964 design and the later cars don't do it.

les mans · 05-04-2012, 10:14 AM

This is possibly the fan at the rear of the ccu, which on my 964 starts up with
activation of ignition switch. I had removed it several weeks ago because of
excessive noise, but after administering special grease-- is silently turning.

Patronus · 05-04-2012, 10:25 AM

The fans I'm talking about are the two big ones blowing fresh air into the cabin. Not to be confused with the tiny little one behind the CCU. These big fans are always on with ignition, until I unplug the final stage amplifier. Then they stop. I confirmed it this afternoon when I opened up the vent system. Not only do they turn, they turn very fast! Even at zero setting.

RSTarga · 05-04-2012, 01:36 PM

Mine blow all the time too

Patronus · 05-04-2012, 01:42 PM

Well maybe I can't stop them from blowing all the time, but at least I managed to resolve the hugely irritating squeak that one of them was making. Now they won't bother me any more.

RW964 · 05-04-2012, 02:28 PM

Just my point two cents.
My 90 964 fans run all the time even at the lowest setting. I am thinking that if you have your a/c on you need some kind of air flow so that the coil does not freeze up. So maybe the good ppl at Porsche made it so that the fans runs no matter what even if the a/c or heat is not on kind of a fail safe deal.
Dunno but a lot of talk on this and seems to be common .. Still a great car...

MarkRobinson · 05-31-2012, 11:22 AM

So who's the recommended source for rebuilding our blower units if we have continued problems such as it staying on or sometimes losing power as mine does. :/

dick911 · 05-31-2012, 11:43 AM

As far as I know and experienced last 18 years

(and also mentioned in Adrian's 964 book) the fan in a 964 will always be blowing, even when selected 0 (zero) but... with ignition on ! I'm not sure but it is for safety reasons to keep fresh air circulating in the cabin.

Also the little fan at the back of your CCU will be continuing for at least 30-60 seconds after you turn off your ignition/engine... sometimes a bit longer

Regards,

Dick911

porterdog · 05-31-2012, 07:09 PM

Quote:

Originally Posted by MarkRobinson

So who's the recommended source for rebuilding our blower units if we have continued problems such as it staying on or sometimes losing power as mine does. :/

Loren is pretty helpful but can be irascible...

GeorgeK · 06-06-2012, 12:26 AM

I went through this recently. NOT easy by any means.
See:

Project Shrek: AC, ventilation, a discovery and a silly Q - Rennlist Discussion Forums