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Another CCU battery draw

My CCU seems to be drawing .3 amp after I turn the car off, it will eventually drain the battery. I traced the draw to fuse 1. If I pull the fuse and put it back the draw is gone; I have to run the car to cause the drain.

I put my head under the dash and the fan isn't running, I even unplugged it just to be sure it had no effect on the amp draw.

I've searched around the forums. Possible ideas include the fan is dead and the little transistor is still leaving the fan circuit energized, or perhaps the CCU is not turning off on its own.

Any ideas?

Also, I've been looking for a reasonably priced refurbishing service. Cosmetically my unit is in mint condition so I really don't want to exchange it.

I've got the Blaupunkt tools coming so I can pull the unit. If the fix is not too tricky I can probably fix it.
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'66 912 - Polo Red;
'74 911s - Silver Carrera RS clone
'77 911s - Peru red IROC Clone
'89 964 C4 - Guards red
Old 09-19-2017, 09:05 AM
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I am having a problem with battery drain on my 92 C2 which started with a residual drain of .47 amp. This draw was traced back to fuse 1. The ECU was pulled and a faulty transistor replaced (Thanks Tore B!). The draw was reduced to .05 amps, about normal I think with a aftermarket radio. A new battery was just installed. The alternator was pulled and tested ok but had the voltage regulator replaced anyway. The drain is still .05 amps and the battery is STILL discharging over a couple of days. How can this be? Anybody with any ideas would be greatly appreciated!
Old 09-19-2017, 10:15 AM
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I had a second drain earlier this year, my driver's side door switch for the cabin lights was intermittently touching the body. Perhaps your issue is not constant?
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'66 912 - Polo Red;
'74 911s - Silver Carrera RS clone
'77 911s - Peru red IROC Clone
'89 964 C4 - Guards red
Old 09-19-2017, 10:44 AM
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That's interesting. I actually thought that may have been a problem on my initial checks and even bought a couple of spares but didn't change them. If the door switch was intermittent would you not see the interior light go on and off? Is there a check for a faulty door switch?
Old 09-19-2017, 04:40 PM
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If your windows work after you open and shut the drivers door then the switch is bad, sometimes a spray of contact cleaner can remedy the problem
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what condition my condition is in
Old 09-19-2017, 05:09 PM
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My power window regulator remained energized, however not enough to operate the windows. The door switch had an inch of exposed wire that would come in contact with the body, but only periodically.
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'66 912 - Polo Red;
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'77 911s - Peru red IROC Clone
'89 964 C4 - Guards red
Old 09-19-2017, 05:27 PM
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Jeff777, do you have an aftermarket alarm installed? These can cause a draw even when functioning normally. Mine fitted by the previvious owner caused a draw over the frunk light circuit that took a while to localise. Got the draw down to about 35 mA. A general observation after 12 years ownership, these cars eat batteriets if not driven regularly.
Old 09-20-2017, 05:46 AM
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No, factory alarm. I'm the original owner so should be no surprises with the car. This battery issue just started this summer. Looking at door switch now.
Old 09-20-2017, 09:11 AM
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Anyone on the forum good at diagnosing CCUs? Once I have mine out, I'm hoping to figure out what's wrong with it at home.
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'66 912 - Polo Red;
'74 911s - Silver Carrera RS clone
'77 911s - Peru red IROC Clone
'89 964 C4 - Guards red
Old 09-20-2017, 11:29 AM
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https://www.bergvillfx.com/ccurepair Try this link for info.
My fan runs after changing out the ignition switch and R12 to 134, my problem might be the switch.
I cut into the 12v side with a toggle switch,flip it off if the car sits, on, the air and fans work fine.
Summer will be over soon then I'll look to see what the fix involves also try a battery tender.
Old 09-20-2017, 05:06 PM
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I removed and disconnected the CCU. The current drain went from .36 amps to .02. The battery is no longer discharging abnormally so the culprit would seem to be the CCU. Time for a rebuild?
Old 10-14-2017, 03:35 PM
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I had this problem on my 964. It was the transistor mentioned in this Rennlist thread. I replaced the transistor and it's working fine (for maybe 5+ years now) without draining my battery. I hope this helps.

https://rennlist.com/forums/964-forum/359909-strange-ccu-issue-opinions.html
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Old 10-16-2017, 11:45 AM
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Thanks for the info. I’m sending my CCU in for repair. Hopefully that solves the problem.
Old 10-16-2017, 04:46 PM
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BTW, the transistor (BC337) that I'm talking about costs less than $1. It's a nice DIY project.
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Old 10-16-2017, 04:50 PM
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Quote:
Originally Posted by Jim Richards View Post
BTW, the transistor (BC337) that I'm talking about costs less than $1. It's a nice DIY project.
Sounds great. Is it documented somewhere?
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Old 10-16-2017, 07:25 PM
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Somewhat, in the link I previously posted (above).
Old 10-17-2017, 09:17 AM
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