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YOUR RESEARCH996 C4 cab and battery drain
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Check quickly
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Suggestion · Original poster
just wanted to check that there isn't something obvious I can check quickly?
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Suggestion
I'm always a proponent of DIY repairs, but if it is a motor that's running continuously, I'd be worried about cooking it before you finish troubleshooting.
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Suggestion
I'm always a proponent of DIY repairs, but if it is a motor that's running continuously, I'd be worried about cooking it before you finish troubleshooting.
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Hi all,
When I park and lock the car, but with the top down... the car can barely start an hour or so later. With the top up it will start without any issues weeks later. Battery is fairly new and has no issues, other than when parking with the top down!
Before I go tracing this... just wanted to check that there isn't something obvious I can check quickly? Alarm sensors possibly draining the batter when the top is down?
This is on a 1998 996 C4 cab. Standard alarm etc. no other mods.
Thanks!
Welcome!
Since the battery drains in an hr, you'll be hunting for a big current consumer. It's possible but I doubt alarm sensors use that much. It's more likely some actuators like motors. Do you have a multimeter and plan to troubleshoot it yourself?
Ah interesting, very good point about big drain. Hm, could be then the roof motor not switching off even though the roof seems folded.
Yeah I have a multimeter, was going to try an initial troubleshooting myself for sheer scientific gratification. I'm guessing the fuses would give a good way to track it down?
Thanks!
From the wiring diagram, you have 5 motors plus a ton of related microswitches and potentiometers to operate the TOP and detect its position. Try fuse D3 (30A) first, the one that powers the TOP motors and the control unit. There are also B1 (15A) and B5 (7.5A) that supply power to the control unit.
Maybe just leave the TOP open, then remove D3 and lock the car and see if the drain happens again.
I ask because I don't see any reason to even lock a convertible car if you leave the top down. Are you having problems with the hood not going up? If you are, maybe that's the route of your drainage problem. If not then put the roof up and see does the problem go away. Save all your assing about looking for something that can be averted. 2 good reasons I would put the roof up on leaving the car would be:- To stop the jealous type from spitting on your seat and worse again in the case of a down pour of rain.
Classic Hurdi...How to fix a battery issue with the top down: don't put the top down.
ooo...one of those motors burning out may cost more than an hour or two of diagnostics @ an indy shop. I'm always a proponent of DIY repairs, but if it is a motor that's running continuously, I'd be worried about cooking it before you finish troubleshooting.
The alarm is armed and the car is immobilized when it's locked. If you invest in the "red clip," you even get even better alarm action...
Keep in mind that the C4 cabriolet has the most computers of any 996. It is also notorious for not wanting to "go to sleep." My C4 cab would last about 3 days with the alarm on when I was out of town and then be completely dead. They eat batteries for lunch. Go with the largest in the class that will fit. IIRC, you can get a 850-1050AH one that will fit...
As to Hurdi's comments- while I agree with the notion that locking a cab is a bad idea (and I left my '87 unlocked all the time) the 996 cab has to be locked or the computers will stay active. Locking it with the key will put it in full sleep mode. Are you locking with the remote or the key? If the not the key, I would start there and see what happens.
Cheers,
Tom
Thanks all for some great pointers! Yep agree with the comments about arming/immobilising with the roof down, that's why I've been locking. Not so worried about spitting, I'm the poor man "anomaly" in my area with a '98 911...
Good points. Re your question above, I'm locking with remote. Haven't tried with key, will give it a go too.
Ok my Google skills are failing me... what's a "red clip"?
BTW, if you have access to Durametric, you can retrieve error codes from the TOP control unit and that should give you a much better clue if something is not in working order.
Oh sorry I didn't realize he was having a battery issue. Wouldn't he hear a motor that was still running or at least HUMMING or at least smell it burning. Why the hell someone should lock a car with the convertible top DOWN beats me. The only time I would lock mine when the top was still down, would be in my own locked garage. (locked takes less from the battery than unlocked)... Explain the 'red clip' for us un-initiated. Do you mean steering lock which fits over the steering wheel and brake pedal. If you do, the 911 has the locking steering wheel anyway.
BTW if you hear the horn 'beep' when locking, then the car is not armed. (its still unlocked and taking more from the battery to keep it unlocked than locked).. Of course Schnell may know something more about the alarm system on these cars than I do. Or we may never hear from him again on this subject. Mine takes 5 days to go in full sleep mode. After that time I have to unlock via the key and all returns to normal. With the top down the 'movement detection' for inside the cab is not or cannot be working, so that will take more from the battery to keep that system open then it would when working. Makes sense to me.
From the Boxster forum:
"The Red Clip (PN# 986.504.986.00) was originally part of the Speedster Pkg.
It's function was to act as a Fail Safe to prevent the convertible top from being closed when the Speedster Humps were installed, which would have damaged the top mechanism and the Humps.
It was serrendipitously discovered that with this clip in place, in addition to preventing closing the top (because it disabled the top motor circuit), that it also activated the interior IR motion sensors.
The benefit of this was that with the clip in place, the top could be left open and the IR system offered some degree of protection from people reaching into the interior of the car. I say some protection because the system can be defeated by either swift or very slow motion which the system does not detect.
Porsche intentionally defaulted the IR sensors to inactive with the top down in order to prevent false alarms when say a bug flew into the interior, or a leaf fell into it, etc."
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