bmwtinut

Well ever since I bought the car back in Oct 2013 the CCU was iffy. Had trouble on the drive back on with the AC and heat being intermittent. You would tap on the face plate and it would come on. All fall and winter it would be hit or miss if the AC/Heat/Fan would turn on. Now it has not been turning on at all. The CCU head is lifeless. It is back-lit when you turn on the head lights but none of the buttons do anything. Checked the fuses on my drive back in Oct and they all were good.
Checked the fuses last night and things are a different story. The #1 fuse was charred and melted but not blown. Took it out and realized that it was a 40A not a 25A that it should of been. Melted some of the fuse box as well.



Just wondering where to start in trying to figure this out.

Also if I disconnect the CCU and remove it from the car can I still drive it or are other essential items routed through the CCU.


Here is some additional information from the pelican forum on the cars CCU issues from the owner that I purchased the car from.
http://forums.pelicanparts.com/porsc...e-control.html

Thanks

Rocket Rob

Its my understanding that the oil cooler fan power is routed through the CCU but hopefully, someone can confirm this. Otherwise, you are safe to drive it without.

964George

Hi bmwtinut

I also have a similar CCU issue, fuse 1 will blow if I turn the fan speed to 2...
If I keep the fan speed at zero I can adjust the heat fine and everything else works.
I just don't touch the fan speed or defrost button!
Plus I don't have AC.

Replace your fuse and have everything set to minimum then see if you can dial the heat up?
Let me know how you get on?

Also do you have access to a scan tool to see any CCU error codes? It may help sort your problem.
I think Rob may be correct about the oil cooler fan, I vaguely remember reading it somewhere

RayB_911

I had to replace both interior blower motors. Check out ToreB website on CCU. It was helpful. You can search for links to his website.mi don't have handy.

Prepare to spend if you have to replace the blowers. Takes a bit of time. Mine were basically seized. I kept them and oiled the "bearing" for awhile. But they never loosened up. They need a rebuild or trash.

Good luck.

pcarplayer

is this the one ?

http://www.porschehvac.bergvill.com/

964George

^^^^^^^ yes that's it

ToreB

That's it yes. Thanks.
Fuse 1 is, as mentioned above, for the front fans. They are known to wear out these days, and will cause excessive current in the circuit. Full fan speed will increase the current, and thus blow the fuse if there's any issues.
It is possible to drive without the CCU, but you will have a no oil cooler fan operation, so keep an eye on the engine temperature. The rear/aux fan will also be no-op, so the additional cooling after engine shutdown will not be working.

I suggest to test start with testing both front fans, and change any worn motors. Here's a thread with some tips, there's several more on this topic. The burnt terminal in the fuse box should be changed to prevent future problems.
I am sure the CCU can be brought to life again. I would start with testing the power supplies in the CCU harness, but the unit might need some work since you previously have had intermittent failures.
Cheers,
Tore

bmwtinut

Well I don't want to curse myself but I left work yesterday and the fans roared to life when I started the car. I did put the correct fuses back in the correct locations when I discovered the 40A one though. Now it is the next morning and I have full control of the CCU now. Everything is working from what I can tell. Hmmm.

Lorenfb

"I would start with testing the power supplies in the CCU harness, but the unit might need some work since you previously have had intermittent failures."

There are three critical powers; #30, #15, X. All must be present for full functionality of the CCU.

Read here for more info under 'Porsche CCU 964/993';
http://www.systemsc.com/problems.htm

tbennett017

Just a question, Tore... you are indeed the expert in these systems, but I would guess that the front oil cooler fan would go into failure mode and run with no power on line 16... That is how one can install a manual override, by interrupting the signal on that line.

I'd be curious if that is true, or if the front fans are also dependent on other lines through the CCU too?

ToreB

Thanks for the feedback Tom. No fans will run at all with the CCU out. That means the A/C condenser, oil cooler, two interior and rear aux fan. (and the CCU fan as well :-)
The 964 CCU have a oil cooler feedback circuit that supervise the fan, but as far as I know will this only produce a fault code in the CCU if the fan does not work.
I haven't looked into the details of what people do when they insert an oil cooler override switch, but I would connect it on the CCU harness, that's pin K22.
Cheers,
Tore

backitoff

I would check all three fan motors. If they tighten up as they get hot they may draw too much load and cause the fuse to blow. I'm no expert but it seems logical?
Most of my issues were down to the motors being partially seized through lack of use. I took them out and really cleaned and lubed them up and they work fine now. Even the one in the back was the same.

bmwtinut

I added a link in the original post to the pelican forum where the owner that I bought the car from was having some issues. ToreB was discussing it with dfink (owner)

One the drive back from Nebraska, we had to tap on the CCU to get it restarted at times.

ziu

I took an old relay(with 2 coils) removed the interior and than I ´ve installed a switch with the positions low -0- high, that fits for all fans of AC; oilcooler and in the engine bay.

backitoff

I bit the bullet and bought another CCU thinking mine was faulty. I figured that even if it didn't solve my problem it was worth having a spare seeing as they are now obsolete. As it turned out my CCU was fine.Doh!