pchansen1

I've been having trouble with my defroster flap servo motor. This is the far left servo up against the firewall when viewed from the front of the car. Initially I diagnosed it as a faulty servo. I even went to the trouble of dissecting the servo and discovering a burned spot on the printed board that the contactors ride on (for those of you who have seen one of these things open). I ordered a used one from DC automotive for $117 (shipping included) and when I received it, I plugged it in and....nothing. I then took the DC automotive servo and plugged it into the far right servo motor's plug (this one controls the foot air) and....nothing. Plugged the right servo motor back in and....nothing. Oops! This also blew fuse #1 and killed the whole CCU. I replaced the fuse and the CCU will now run the fan and cycle the A/C normally but now NONE of the three servo motors that are in view up against the fire wall will function.
Here is what I now assume happened. The original malfunctioning defrost servo motor jammed and burned a spot on the printed board and then somehow back fed electricity into the CCU and damaged it some how. Then I plugged in a "good" servo. It still didn't work because of the damage to the CCU. By plugging in the "good" servo motor to the far right servo motor's plug (obviously not the same wire pattern although the plugs are identical) I damaged the CCU even more. So, my question is does anyone know where I might get my CCU repaired? I called around and found LA Dismanlers had one for $450 with a one week warranty! Anyone have one they'd like to sell?

Thanks,

Paul
'95 993

ToreB

Some repair info here:
http://www.porsche964.co.uk/technical/climate.htm

I've changed a couple of the Siemens TCA2465 inside CCU's with good results. I also agree with you, I suppose you've blown a PCB track or something as well as one or more of the Siemens IC's. It's obsolete I'm afraid, so you may have to get a defective CCU for spare parts.
I found out what was wrong by just looking on the PCB, it was slightly burnt around one of the TCA's, changed it and everything worked.
Good luck mate, keep us informed of any progress. If you decide to ditch your defective unit, I'll pay the shipping cost to my hardware graveyard in the basement instead...
Regards,
Tore

ninjabones

Dougherty's in West Chester PA is currently dismantling a 993 that wrecked a few weeks ago at Summit Point. Car was a friend of mine's and was in very good shape before the wreck. Give Bill Dougherty a call at 610-692-6039.

pchansen1

Glen,
Thanks, I will.

Tore,

Thanks for the response. I'll see what Bill Dougherty wants to do and we'll take it from there. I still can't believe switching servo motors would cause so much damage- especially when the plug patterns are the same.

pchansen1

Tore,
Please check this site out. http://www.1sourcecomponents.com/partinfo/tca2465.htm I haven't had to chance to pull the CCU yet but do you think these TCA 2465's would work?

Thanks in advance,
Paul

ToreB

I agree, but maybe the used servo you tried is defective? Pry it open and have a look.
I've seen a lot of notes on defective servos frying the TCA IC inside the CCU, including the one I linked to above. This is the driver for the servo, maybe the burnt tracks inside the servo feeds wrong feedback signals to the opamp control loop and fry the internals. I could easily see the heat marks on the PCB below the IC.
I've changed at least four of my servos, all of them had burn marks like all the other pictures I've seen, but my CCU have survived. :-)

If the supplier you linked to can deliver the IC in a P-SIP package I would think it would fit perfectly.
My experience with such multi-channel suppliers is that they really do not have the components in stock, only estimated numbers of components are given on initial contact. Contact them and ask, if they have them i SIP I would also be interested in some.
Regards,
Tore

Stealth 993

the servos burn out, that is normal. You may have purchased a bad one, I doubt they check them. What you can do, is remove one that you know works, then put it on the one that doesn't & see if it moves. Mine just burnt out as well, & was replaced. I found out from my duremetric software. when plugged it, it reads the CCU & tells you what servo isn't working.

pchansen1

I'm running into dead ends everywhere I look with respect to locating these pesky IC's.. Still trying.

ToreB

I was afraid of that, you have my sympathy mate...
Regards,
Tore