jbarreto

I am placing 993.659.047.00 CCU into my 1989 C4. I have read that I have to jump pins G1 and G19. How do I identify them? Do I just use a short length of wire to jump? Thanks

ToreB

There's two connectors at the back, G and K. Pin numbers are printed on the connector.
G1 and 19 are the two feedback voltages from the rear fan. The (993?) Turbo has two rear fans, therefore you have to bridge these two to avoid the CCU going into a fail safe mode and shut down the front fans.
This kind of bridge can be done by using either a short wire or a common cheap clamp-on connector.
More on the CCU details page here:
www.porschehvac.bergvill.com

Cheers,
Tore

jbarreto

Tore, Thanks. You have a great site.

found the 2 pins and jumped.
Fans speeds work fine.

Only getting A/C through top right defroster vent and lower left footwell vent.
Then when I press top left A/C button on CCU the A/C blows strong through the driver footwell vent only. Even with slider controls properly adjusted A/C is not coming through any of the center or side vents. Any idea?
Thanks,
John

ToreB

Hi, thanks. You may have one or more inoperative air flap servos. Test them all, see how to on my web site.
Cheers,
Tore

klr10

Hi Tore, thanks for your brilliant website. I looked at your CCU details page as I was also interested in what needs to be done to an earlier car for it to use a later CCU as I understand from Adrian's book they are year specific, although further details appear a bit sketchy in the book. Your link on CCU details appears to have some text missing at the bottom of the page (tried it with Chrome and Firefox)
Kind Regards, Keith

ToreB

Thank you for the feedback Keith, I have now fixed the text box on my web site.
I'll be happy to include more specific info on using a 993 CCU in a 964. I'll make a new chapter on my pages. Write all things you can find in this thread and I'll publish them.
Cheers,
Tore

Lorenfb

"I am placing 993.659.047.00 CCU into my 1989 C4. I have read that I have to jump pins G1 and G19."

And that's the only 993 CCU that can be used. None of the other ones
will function properly even with the jumper. There appears to be
mis-information relating to using a 993 CCU in a 964.

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

ToreB

Loren, feel free to share any knowledge on this.
As far as I know, all CCU's can be used in all 964 and 993 versions. However, it might require some rewiring of the CCU harness/connectors. The main differences between the three (964,early 993, later 993) CCU wiring schemes are: Right rear fan feedback line, outside temp sensor, reverse gear signal, condenser Stage 2 signal and resirc valve output.
Cheers,
Tore

Lorenfb

"feel free to share any knowledge on this."

The use of a 993 CCU in a 964 has been an unresolved issue of mine for many years
with conflicting info being found.

Recently a 964 owner sent his 964 CCU to a competitor and received a 993 CCU
(993 659 047 01) as a replacement because the competitor indicated his 964 CCU
was non-replairable. The customer had problems with the CCU once installed,
e.g. blowers turning on high speed once the ignition switch was turned on,
and sent the unit to me after receiving a refund from the competitor.

At this point two issues had to be resolved, i.e. fixing the 993 unit so it would function properly
in a 993 and also converting it to function in a 964. After fixing most of the customer's basic
993 CCU problems I focused on the 993 conversion. The mod being mentioned was to jump
G1 & G19 on the 993 CCU. This seemed to work until the fan speed was increased to about
the '3' position at which point the F/R blowers cycled to low and then high speed.

At this point the Porsche tester was used to evaluate the CCU fault codes and then to reset
them. Once the fault codes were reset, both the 993 CCU (993 659 047 01) and the 964
CCU (964 659 047 00) functioned identically in the 964. So there shouldn't be any problem
using a 993 CCU in a 964. When strange CCU problems occur, the Porsche tester needs
to be used to evaluate and reset any fault codes to prevent abnormal CCU functioning.

Bottom line: To assure compatibility, minor mods are necessary as noted in a later post.

Lorenfb

The Porsche document (87.27) about jumping pins G1 & G19 only applies when
using a later 964 CCU, e.g. 964 659 047 01, in an early 964 where the wiring
didn't jump those pins. That mod does not facilitate using a 993 CCU in a 964.
This mod was needed because of the 964 659 047 01 being make available for
the 965 (turbo) with dual rear blowers and the early 964 (pre '91) wiring not
having the adequate wiring to interface with the '01' pre-993 CCU.

Partisan

It depends on the software release. The early 993 units contain H03/H04, which runs without issues in the 964. If necessary, G1/G19 must be shorted (turbo not, later 964 not).
The safest way is to make an OBD scan to be sure about the release. Sometimes the CCUs cases do not contain what they should...

H07/H08 (which is the last) can be used, when an outside temp sensor is added. Condenser and oil cooler feedback must be disconnected.

I think the best way is to downgrade a 993 CCU to release H03/H04. Then the car can stay in its original state.

Lorenfb

The wiring is as follows:

1. all 964s (964 659 047 0X), early 993s (993 659 047 00)

G7 - condenser blower feedback
G9 - oil cooler feedback

2. late 993s (95/2) (993 659 047 01)

G7 - backup light switch
G9 - outside temp sensor

A simple solution to using a late CCU is the following:

1. Cut G7 input track and ground the other side of the cut.
2. Cut G9 input track and add a 2.7K resistor to ground on the other side of the cut.

"I think the best way is to downgrade a 993 CCU to release H03/H04."

This is not possible without re-programming the microcontroller and probably
not at all possible because it's mask programmed.

Partisan

Hi Loren,

yes, this is the most simple solution. With a 2k7 fixed resistor the outside temp will read as 27°C (80°F)
What does the software with this value? I don't know exactly.

Me personally, I don't like doing quick modifications. If this CCU will be later mounted in a 993, some functions will not work correctly.

Sure the processor can not be reprogrammed. This technology is from the early '90. Embedded Flash was far away.
The processor module has an (mostly) unpopulated place for an EEPROM. There you can put any code you want. Sometimes there is a H07/H08 mask programmed processor together with a H03/H04 EEPROM. By Jumper the processor is told which code to use.


Cheers,
Michael

Lorenfb

"The processor module has an (mostly) unpopulated place for an EEPROM. There you can put any code you want. Sometimes there is a H07/H08 mask programmed processor together with a H03/H04 EEPROM. By Jumper the processor is told which code to use."

Actually, a basic EPROM could be used with the most likely Intel 8397 16 bit
processor by grounding the PLCC pin 2. Non-volatile data memory for fault
codes is stored in the 256 bit serial EEPROM. Probably during development
or early production, an external EPROM was used. This also gave Porsche
the option to have a generic programmable CCU available for low production
models if they were ever released to manufacturing.

ToreB

I've seen several CPU's used in the CCU, mostly Siemens 80C515/80C535. Here's a couple of examples.
Cheers,
Tore