Climate Control Unit (CCU) and OBD

jboult · Oct 31, 2012

My car has been at the indie for a few days having various bits and pieces done, including a new a/c condensor. While it was there I asked them to check a strange problem that I was having with the heating, whereby it was generally running fine, up until a certain road speed (or possibly distance travelled), and then I would only get cold air. I assumed a stuck servo or bad CCU fan was to blame. The indie also noticed that the OBD interface wasn't working and said they'd have a quick look at that as well.

Anyway... Just had a call to say the CCU seems to have a problem, possibly shorting, and this was effectively disabling the OBD. Replacing the CCU with a spare they happened to have for diagnostic purposes brought the OBD to life instantly. I don't know if it fixes the weird heating problem (I'll find out when I drive it). Anyway, the CCU unit they fitted will only be on temporary loan while I find a replacement or have mine repaired.

So - does anyone know a reliable repair service for these units? Alternatively anyone have a working a/c enabled 2nd hand unit they're selling?!

Also, any advice about the above. I'm thinking that the rear fan may have failed previously, which might account for the strange heating problem, and that over time something else inside the CCU has failed which causes the problem with the OBD.

Cheers/John

jboult · Nov 1, 2012

Maurice,

Yes, overloading was my thought too, but the fan seems to turn freely enough. Anyway, the only conclusive thing I can say is that with a different CCU in the OBD fires up fine and the heating works as expected.

So - if anyone knows of a reliable repair shop or has a CCu for sale let me know!

Cheers/John

colt · Nov 1, 2012

I don't know of any company who can repair the ccu, so it would appear to be a used item and taking a chance, I have only once experienced the exact same problem as you of a ccu control unit affecting the diagnosis plug,In this car also a targa metallic black with a cashmere interior from memory, no control units were visible until i disconnected the heating ccu.
Have you definitely been on a long enough journey to say the ccu was the cause of the heating regulation issue?

Regards Christian.................

jboult · Nov 2, 2012

Christian,

Thanks for the reply. As with a lot of these things on 993, we're left trying to piece together the evidence to find out what's going wrong. The only thing I can say with certainty is that with the old CCU plugged in, the OBD didn't work and on long journeys the air would just get colder and colder (it may also be speed related, as I'm sure when I slowed down e.g. leaving a motorway, the heater would blow warm again). I know that with the loan CCU in the OBD works and the heating is fine in normal use - I haven't been on a long enough journey yet to tell if the getting colder problem is cured, but it looks likely.

I've found a couple of places in the US that do repairs, but the only testimonials I've found are from their own site. Much cheaper than buying a new unit, even with the carriage charges, but obviously a gamble. Would prefer a known working 2nd hand unit at a reasonable price, if such a thing exists! Alternatively, I'll swap the old unit back in, put up with the cold air on long journeys and remind the indie to unplug it when checking fault codes!

Interestingly I found a large stack of bills for the car on the side at home last night. I suspect the wife is making some kind of point...

Cheers/John

colt · Nov 2, 2012

John, does winding up the temp dial a bit restore the heat or only if you turn up to the max??

With the car i worked on only the diagnosis was disturbed with the heating ccu fitted ,it worked fine in other respects as far as i can remember.........

jboult · Nov 2, 2012

My impression was that it got colder quite quickly, to the point where if you wanted any heat at all it needed to be on full. Driving down the M4 in the snow last winter wasn't much fun!

Cheers/John

Jamie Summers · Nov 6, 2012

John,
I know of several places that repair the CCUs, on Rennlist in the US there is a guy called Loren FB who does repairs. There is also a guy on 911uk.com called Torre B who is based in Scandinavia somewhere who repairs them (probably best bet) and there is a place in Italy that does them. No one in the UK that I am aware of though ........ Sorry don't have any websites to hand ...........
Otherwise look on eBay - they come up pretty frequently. I bought a 2nd hand 993 one which replaced the knackered one in my 964 RS. I keep meaning to get the old one repaired, but have never got round to it (won't be any use to you though as the 964 version wont talk to a 993 so I understand).

Jamie

colt · Nov 6, 2012

I don't think that all faults can be repaired ????? From what i can see only basic component faults can be repaired by third parties. The temp "drift off" problem affects lots of cars and apart from people suggesting that dust on the inside temp sensor and non functioning of the vent fan for it ,are known causes there appears to be little known about it. To my mind if one or two companies were able to fully test and repair these units then the cause of this common problem would have been long established and known to the enthusiasts many years ago?? I have used the official porsche software to diagnose and test the system on many occasions ,replacing items such as fresh air flap motor and left and right mixing flap motors as common causes(other than the aforementioned two), not always with total success. The temp sensors (rear engine air inlet to blower, evaporator(only Air/con), outside air,mixing chamber left&right) and cabin temp) rarely fail. It's a complicated system and of an old design and literature about exactly how i works is scarce. So it somewhat of a mystery at times.
Many owners only use the car in the warmer months and don't go far enough to realize that the system is not functioning quite as it was when it left the factory,indeed if we take the the number of owners who elect to leave the air /con side of it in a non working state then some would not be worried if the heating didn't work quite as it was designed to?
Christian.......

horse · Nov 8, 2012

Hi,agree with Colt. I have the problem with the passenger side footwell flap closing slowly over about a mile so no warm air is let through. I swapped the drivers side over and it did the same. Checked all the servos worked in the front and then sent the CCU unit to ECU doctors in the states, they replaced a couple of pots and some cold joints sent it back with a five year warranty. Does it work?. No. They sent me a lhd tester unit to see if the flap would work but I got the same problem.
Very good company refunded all costs bar postage. So what to do?. The system works fine apart from this one servo so I am going to put a manual control through the carpet on a dial system, shut to open. I would like to fix it but there you go.
For anybody interested there is a new CCU unit on Ebay at the moment, very rare indeed, keep trying. Horse.

jboult · Nov 12, 2012

Horse,

Out of interest, did the LHD unit fit Ok? I've seen a few up for sale, so this might be an option. Otherwise I may try the ECU Doctor route. I know mine is definitely a CCU problem as the loan unit makes everything work fine.

Interestingly, I've noticed that I get warm air much more quickly now, so I guess I had a long term problem without realising it, as ever since I bought the car (~4 years ago) it's always taken quite a while to get warm.

Cheers/John

horse · Nov 12, 2012

Hi, yes it did fit, but the fan is on the other side. Also the control panel is the wrong way round. I took the front part off mine and plugged it into the front of the l.h CCU. Not sure if the wring is the same but the chaps in the States were happy for me to try.
My advice would be to get the correct unit, remember up to 95 and after 95 are different units. Most of the breakers think they are all the same. Check the numbers out and only buy the same as the original. Horse