ataman

Dear Adrian,

First of all, I really appreciate your help and advice.

General Information:

1. I am living in Ankara, Turkey.
2. I bought my 993 1995 C2, LHD, Manual transmission three months ago. So it is a used car.
3. Since its CCU was not working, I replaced it with brand new one. I bought the CCU online, www.vertexauto.com during my trip to USA. The part number is: 993 659 047 01. I have checked it again when I got your email. I am sure on its part number. It is made by Hella, Made in Germany. Old CCU had not AC MAX button. The new one, mine, has.
4. I tried to find the model label on the underside of luggage compartment lid. But unfortunately, I could not. I think my car¡¦s old owner was removed it during painting.
5. Here is my car information which might help your analysis:
1. Chassis No: WP0ZZZ99ZSS314686
2. Motor no: 63504612
6. My car is in my closed garage when I don¡¦t drive it.
7. During your suggestion test; the environment temperature was 18 degrees C

Here is my test report according your instruction:

Since I had pull out the fuse of blower inside compartment (which is located in the trunk fuse box, #1 position) in order to prevent potential battery flat situation; firstly, I replaced the fuse. The fan did NOT begin to run spontaneously at that moment.

1. Before applying power to the 993 turn the temp control **** to the blue dot position and check the rear blower fan is not running
„³ No, it is not running at that moment.
2. With the engine running turn the temp **** to the red dot position and ensure the fan starts running at low speed.
„³Yes, fan starts running at low speed
3. With engine running turn the temp **** back to the blue dot position and make sure the rear blower fan turns off. This may take some time.
„³ No, the rear blower fan does NOT turn off. It is running. I waited for 5-7 minutes; still running.
4. Turn the temp control **** to 27. The rear blower fan should start running. The select the blower speed to 1 through 4 and make the fans run at the selected speed. Then turn fans off.
„³ Blower speed works, but unfortunately I could not manage to turn the fan off.
5. Turn the temp control **** back to the blue dot position. Make sure rear blower fan turns off.
„³ I turned control **** back to blue dot position; the fan did NOT turn off.
6. Select defrost. Make sure the rear blower fan cranks up, the aircon may also engage, make sure the fans up the front crank up to maximum speed and make sure hot air is blowing out of the side vents and the windshield vents.
„³ OK, everything is working well
7 Go for a drive. At least 15 minutes. Take a pen and paper with you. Keep the temp control **** at the 27 position or around this area. When you get home let the engine idle and record the engine temperature pointer position. Turn engine off. Does the rear blower fan keep running?
„³ I drove 25 minutes with temp control knot at 27 position. The engine temperature pointer was below the middle line. I mean, the pointer was showing the third line from bottom. After turning engine off, the rear blower fan kept running. It took 23 minutes to stop it by itself. Actually it stopped after 15 minutes; the pointer was lower than the original position. After a few seconds, it began to run again and finally it stopped at 23 minutes. The engine temperature pointer was showing the second line from the bottom.

Extra information:

1. During fan running, I removed the plug of the little fan in CCU; it did not affect the rear blower. I mean the rear blower was still running.
2. After finishing all of your tests; I turned on engine again for only 5-8 seconds and turned it off. The rear blower begun to run. Without doing anything it took 22 minutes for the rear blower stopped by itself.

I am waiting for your comments and contribution.

Many thanks and regards,

Adrian

Dear Ataman,
I am sure that your problem is the control unit. The fan time for shutting off tends to correspond to the power switching off on the control unit.
Seeing as you are in Turkey you have a full 1995 model. I believe that you have installed a 1996 model year control unit. I have no idea what you had originally because all the 993 units I have seen have the max AC button.
Either the unit you purchased is kaput or it is the wrong one.
I do not have any data on the 1996 and up 993s butr I have the 94 and 95 manual. Let me have a look tomorrow and see what I can find for you. I do not have the TSBs for the 993 aircon and heating control system. I wonder if the like some of the 964s that a modification is required for the 01 control unit.
Ciao,
Adrian
964C4

PS: The -00 unit works in a 964 (91-94) without modification. The -01 does not work in a 964 ever.

ataman

Dear Adrian,

I think the CCU unit which I replaced was not original. Because it did not have AC Max control and its serial number begins 964...... My car's old owner had replaced it.
I have an idea but since I am not sure; I need your comment on it. Whenever I unplugged CCU unit, the rear blower fan stops.
Suppose I install a manual electric switch to (+) pole of the wire which is coming to CCU. I can install this switch a place on the dashboard. As soon as I stopped engine, I can turn this new switch off. ( The logic behind this idea is to create a user friendly fuse plug/unplug procedure)
Do you think it works and it is unharmful solution for my car?
Regards,

Adrian

Dear Ataman,
Yes the 964 unit will not work in your 993. Have you kept it. It will be easily sold into the 964 community. We have to use 993 units nowadays if one fails.
I have checked the parts catalogue and the unit you have is correct for the model year 1995.
I do not like modifying cars to fix problems. In the short term this may be the way to go especially as you live in Turkey.
I would like to you to confirm the operation of the rear blower fan relay. This relay is installed in the engine bay electrical panel. I think in the 993 it is on the left side of the engine bay. When you open it up you will see a large relay. Now open up the central electric in the luggage compartment (where you find fuse No 1) and find the oil cooler fan or aircon condenser-mixer fan relay. These relays should be the same part number as the rear blower fan relay. Swap them over and see if the problem continues.
The next test is to again disconnect and leave disconnected the temp sensor in the engine bay for the rear blower fan. Confirm the problem still occurs by doing the tests I have already supplied.
If the problem continues after checking the relay and the sensor I am afraid the failure can only be in the control unit.
You will then have to decide what to do next. I am wondering if the previous owner attempted to change the wiring to suit the 964 control unit. This sadly starts to get complicated.
I would if you confirm that the ccu has a problem contact the people who sold it to you and see if there is any warranty.
There is a place in Italy that claims to fix these control units. I wish I could be of more help but this is where we are limited by location.
Ciao,
Adrian
964C4

ataman

Dear Adrian,

Concerning the rear fan relay; I have already done this experiment what you advice me. I replaced it with both of oil cooler fan's and aircon condenser-mixer fan's relays. The rear fan was still running. That is the reason I thought the relay was intact.

I disconnected and left disconnected the temp sensor in the engine bay for the rear blower; nothing was changed.

I have contacted to previous owner. He told me that he did not remember. According to his explanation, maybe his mechanic might do some wiring adjustment in order to use 964 unit; but he is not sure. So I checked the cabling of the rear CCU and found no wiring adjustment.

On the other hand, whenever I turn ignition off, the rear blower fan is running for approximately 20 minutes. I tried more than 15 times. Every time fan stopped app. 20 minutes after ignition off. I decided not to modify the system obeying your advice. I will use my car as it is.

Many thanks for your friendly approach and spending your time for me.

bstephans

Hi all:

I'm brand new to this forum. I still have steam coming out my ears after just returning from my local porsche dealership in Westmont, IL. Hoping I might gain some perspective from you all.....

Here's my sad situation

I brought my 1995 993 c2 in for the engine wiring harness recall. For whatever reason, I didn't get the notice from porsche until now. So, I took the car in and had the work done. After getting the car back, I notice the engine fan staying on EXACTLY 20 minutes and then shutting off. ALso noticed the fan inside not working properly, heater not working, couldn't turn the engine fan off by turning temp control to cold, etc. Lots of stuff not working that worked before I took the car in for the recall.

SO, this morning I took the car back to get these issues looked at. THe service manager proceeds to tell me there were a bunch of faults they pulled on the car BEFORE the harness was replaced that point to this problem....AND that I need a new AC control unit (same as in this post...) They wanted $2,100 to do the work! I went through the roof...1) why weren't the faults pointed out to me before...and 2) the car worked fine BEFORE the harness was replaced. Am I suppose to think all of this is coincidental?? They stood behind the fact that the faults were there before... but admitted the service manager should have told me about them.

So...where I sit now is they agree to cover the labor for replacing the control until and will take $100 off a reman control unit. $930 for the part. I'm so pissed...

I have no way to prove the harness worked screwed up the control unit but I'm very suspicious since NONE of these issues appeared before I had the harness work done.

Thoughts appreciated...sorry for the long initial post.....

JasonAndreas

It's supposed to stay on for 20 minutes to help cool the engine after shutoff.

Pull the rear blower motor resistor out of the ducting and then reset the thermoswitch. It almost sounds like they tried to start your car with the battery maintainer still plugged in. Although the airbag control unit is usually the victim and not the CCU. Do the two front temperature mixing chamber blowers work at all?




Call fellow Rennlister Lorenfb at Systems Consulting. He handles control unit repairs for most shops in the USA. So if your CCU is actually damaged he might be able to repair it for probably 1/3 of what your dealer wants. Removing the CCU is very simple, the tools required to unlock the CCU from the dash can be purchased at any automotive shop for $2USD.

bstephans

Thanks for the reply....

see my comments below...

I sent lorenfb a private message... I'll see if I can't track down his number (or company number) and give him a call.

Thanks for all the advice..

Brian

bstephans

Jason:

One other comment on my reply... it doesn't seem to matter what fan setting I choose, very little to no air comes out of the vents. I hear something changing speeds as I go up the various fan settings, but nothing comes out of the vents...

Also, I've heard that turning the temp setting to the coldest setting is suppose to turn the engine fan off in back -- it doesn't on my car. The fan runs for 20 mins irregardless of temp setting.

Thanks.

JasonAndreas

Did they happen to tell you what the codes were? To properly troubleshoot the CCU based on the fault codes you need to (in most cases) erase the fault codes first and then rescan.

If both the left & right fans are not working then you need to check the "blower final stage" that is mounted on the firewall behind the fuel tank. Right behind the fuel expansion chamber (small black thing on top of the main fuel tank) there should be a small sheet of aluminum mounted to the firewall, make sure the blower final stage is plugged in, bolted to it and not just hanging loose.

Also make sure the temperature sensor in the rear ducting is plugged in and reset the rear blower motor resistor.

So it sounds like the fans are operating but nothing is coming out?

Sorta, with the ignition turned on the setting (potentiometer on the CCU) of the temperature mixing flaps controls the rear blower. If the flaps are closed (temp set to max cold) the rear blower is controlled by the temperature sensor in the rear ducting. 1st stage goes on at 45C and will turn off at 40C, 2nd stage turns on at 62C and turns off at 57C. If the ignition is turned off the rear blower motor will turn on the 1st stage for upto 20 minutes if the temperature rises above 75C and will shut back off when it drops to 70C.