Anyone in SF bay area need a transistor BC337 TRANSISTOR NPN 500MA 45V PHILIPS for the CCU? I have a bagful. Replaced mine and now the little CCU fan shuts off.

 

Is it a bitch to unsolder old and solder in new? Without f_______g the unit up? I used to build Heathkits as a kid, but aren't these new-fangled IC things more delicate? Do you need to use a heat-sink? How much $ to you want for one, in case I ever need it?

 

Changing the BC337 is not very complicated, have a look at my DIY page for details:
www.ccu.tore.bergvill.com

Cheers,
Tore

 

Thanx, ToreB.

 

ToreB: I actually ran into your article about a year ago in diagnosing why my fans cut out shortly after turning up heat (including when pushing the defroster button). Even printed the whole article for future reference. Have read it several times to familiarize myself with the whole system and how it works. To my chagrin, this all happened shortly after buying the car and going through all the "new owner neurotic check-this, check-that crap", and it finally dawned on me months later that I was doing this in the SUMMER! Needless to say, of course the fans quit, because turning up the temperature dial "beyond the blue (cold) dot" proved the system worked perfectly----its automatic! Its not going to blow hot air at me when its already 90 degrees outside. By the way, how did you come to know so much about this whole system and how it all works?

 

Jody, thanks for the feedback, it's always fun to see others make use of my knowledge. I have learnt most of this due to faults in my own car, and partly by helping others in the Norwegian Porsche owners club. I am working on a rewrite of my CCU page to put in more info, but also to try to ease the fault finding a bit.

Funny enough, I don't agree in your conclusion that the fans should stop if the car is in relatively high ambient temperatures.
As far as I know, the front fan speed are only controlled by the fan speed button. In addition to this, the CCU has a sort of fail-safe mechanism that will shut down the front fans if the rear AUX fan is not working properly.
The AUX fan in the engine compartment should start at low speed, then go to high as you turn the temperature **** up. This is done to boost the heated air flow. Ask a classic beetle owner why we need booster fans.
There's a feedback line to the CCU from the AUX fan for fan operation supervision. If the fan motor, low speed resistor or the fuse fails the CCU will shut down the front fans as soon as the rear blower is needed. (when you turn the temp **** high enough)
The AUX fan fuse (placed in the left electric box in the engine compartment) is normally rated at 25A in 964's. This was later changed to 30A.
I suspect you either have a blown fuse or failing rear fan mate. Ask me how I know :-)

Cheers,
Tore

 

Odd, Tore, but everything works perfectly and always has. It was my misinterpretation that led me to try and figure out what was wrong--possibly a blessing in disguise because now I've gleaned the knowledge from you how the whole thing works! To be sure, all the jillions of electric and microvoltage components and checking this milliamp this and that micro-ohm that, is way beyond my ken, especially diagnostically. That's for guys like you. As far as I know, and I know EXACTLY what's been done to my car, those WERE the symptoms on that summer day---fans blew at all speeds as long as temp. **** was @ blue dot and/or BELOW the 21C mark. Anything different, and the fans quit a second or two later! My car had the 30A rear fan resistor replacement way back when the factory bulletin came out, as its in some of the historic service records that came with the car. Both speeds of rear blower do now and always have worked. I decided to "live with it" and not pursue correcting the problem that summer. Then, as I stated earlier, I was chagrinned to discover that there was no problem in Nov. or Dec., a few months later. This is all I know. Maybe there was some DIVINE intervention!?! One other experience that was strange though---one cold night several months ago after a 20 or 30 min. drive, parked, got out, and noticed rear blower running on high. Fairly normal in summer when hot and car hot," but on cold night"? Told myself "don't worry, it'll go off". Of course curiosity (neurosis?) brought me back 5 or 6 minutes later, and fan still blowing full steam. Pulled fuse-off she went. Reinserted fuse-back on she goes! Uh-oh, I aint diggin' this. Pulled relay in rear-off she goes. Plugged relay back in-she's off! Oddly enough, I'd read Babalouie's threads and his story of somewhat similar symptoms that eventuated in having to correct a HUGH mess created by a probably chronically faulty rear relay. Overheated and melted-burned up the whole G.D. female plug assembly, and real SH______TY place to have to work to renovate the whole thing. So, after learning of another RLer's nightmare I immediately bought a new relay! No recurrence since! I'd rather admit to being a little spooked than not acting on my instincts, especially after Babalouie's experience. After all, that relay was 20+ years old, living in a rather hot evironment all its life (electric box cover notwithstanding). I opened up the old relay, and on visual inspection it looks brand new, but who knows! Thanx again for your contributions! I'll let you know in the future if any odd things happen. Cheers

 

Thanks for the info Jody, I have put this up on the wall of unknown CCU behaviour. There's plenty of posts there already!
Cheers,
Tore

 

Tore: Ever since my experience, and thinking about Babalouie's burned up rear blower relay thread, I've often wondered--Was the root cause "the relay itself" or did some other component in this microelectronic cybernetic automotive city throw out an erroneous command for it (the relay) to "TERMINATE". I'm sure you're familiar with the "tin whisker" phenomenon. Can that **** happen with these small voltages, amperages, etc?

 

I haven't looked into the case you are mentioning Jody, but a burnt relay or connector most often is due to a corroded or bad connection. Either internally in the relay or in the connector itself. That causes heating of the connection, which further increase the resistance and heating effect.
Cheers,
Tore

 

Tore, google "tin whiskers" when you've got some idle time. Extremely odd phenomenon! Cheers

 

jody, get a desolder tool from radio shack. sucks the solder right out. use a low watt iron with a fine tip. and don't linger.

free for pickup if you ever in San Jose. I think they make the envelope too thick for shipping in US mail by first class stamp.

 

Thanx, Steve

 

Hi Im new on rennlist
I just bought a barn find 964 that Im restoring is all original I have a question about the ccu transistor because is draining the batery and with the ignition of the ccu stays on ,the quiestion is the transistor has to be only bc337 or i can use bc337-40 I have plenty of the second ones please need advice. the other thing is that the condenser fan in high mode when Ign switch is on, without the air conditioner on, I know that the resistors are bad but in the oil cooler fan doesnt run until take the oil temp swich plug off
my question is the condenser fan should run like that until I change resistor or it is something else?

 

Welcome to Rennlist. Pictures please!
BC337-40 will be fine, this is a non-critical relay switching application. The condenser fan shall run on low speed with A/C on. High speed is initiated by the pressure switch at too high pressure. If the cooling system is empty after all these years, (no pressure) you might have a problem with the pressure switch or its wiring, or the fan speed relay.
Oil cooler shall only run at high oil temperatures, so you describe a normal behaviour. See my DIY pages for details on the fan operation, as well as DIY for the transistor change.
Good luck, keep us informed of the progress.
Cheers,
Tore