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Flat battery - head unit related?

stewart rix

Nurburgring
Joined
28 Sep 2010
Messages
397
Just got back from a week's holiday to find the 93's battery was completely flat - no lights, no clicking noises, no central locking response from the alarm fob etc. So I got the Ctek out to bring the battery back to life, which then brought the alarm back to life (slowly) - the chirping of the alarm got more and more frequent as the battery received the charge, but the alarm wouldn't shut off using the fob (either fob in fact). Eventually it did shut up.

So two questions:
1. does the PA1000 just go into spasms if the battery (and its own back up) has gone dead? Presume it will reset when all charged?

2. I've just had a second hand Becker Traffic Pro fitted - is it coincidence or could it have been wired to cause a constant/permanent drain on the battery? Sound and lights on the unit definitely shut off as normal when the ignition is turned off.
 
No battery issues before the fittment of the Becker? This is where I'd be looking as that's a major drain after only one week.

Ps do you have the iPod connected to the becker in the glove compartment as mine continued to charge when the ignition was off so disconnected it.
 
Did I miss something, have you got your car back?

I've got the PA1000 and never had any issues with dead battery. I disconnect my battery all the time and no issues.

I would have thought it was unlikely to be the head unit. If it was a latch or some thing then alarm would have gone off so you would know.

Glove box light?
 
Dream911 said:
Did I miss something, have you got your car back?

Ah yes, the old turbo. No. Written off. Gone. But replaced! Actually replaced pretty much like for like. Now a proud owner of a 38k mile arctic over midnight blue, R reg turbo, thanks to a contact made through this forum. Bought from a top bloke and clear Porsche enthusiast. Just got to get my GO R1X plate put on it now. :)
 
Connect a amperemeter in series with the battery and start pulling fuses to find the culprit. Normal current draw in a 993 with ignition off is 50 to 70 mA. (0.05A) An aftermarket alarm can introduce an additional 5 to 50mA.
When measuring, note that open doors will activate the interior lights as well as a relay for enabling the power windows. Also, an open bonnet and/or engine lid will activate the lights there too.
After ignition off the CCU with fan will continue to run for 1 to 10 minutes. (circa 500mA)
An unlocked car will also have the OBD LCD with light turned on in the tachometer.

Therefore, measure the current with all interior/bonnet/engine lights off, lock the doors, and wait for the CCU to turn off. You might consider opening the windows first to avoid having problems getting in due to a problem with immobilizer or similar.

A value of 100-200mA or so can indicate that some of the above mentioned points are active.

If the CCU does not turn off (0.5A) you may have a problem with an internal transistor. It's an easy fix for an electronic wiz.

Cheers,
Tore
 
stewart rix said:
Dream911 said:
Did I miss something, have you got your car back?

Ah yes, the old turbo. No. Written off. Gone. But replaced! Actually replaced pretty much like for like. Now a proud owner of a 38k mile arctic over midnight blue, R reg turbo, thanks to a contact made through this forum. Bought from a top bloke and clear Porsche enthusiast. Just got to get my GO R1X plate put on it now. :)

Sounds a great result :thumb:
 
Thanks for that level of detail Tore. Despite being relatively inept when it comes to electronics, I think I'll give that a shot.
 
Thanks for that level of detail Tore. Despite being relatively inept when it comes to electronics, I think I'll give that a shot.
 
It sounds silly, but it is very easy to knock an interior light on pulling a bag out from behind the seat.
 
Checked for anything drawing current today by bridging each fuse in turn with a multimeter. When I bridged the 'radio' fuse I got a fluctuating current - that left me and my neighbour somewhat bemused until his 8 year old some pointed out the flashing indicators. Doh! I'd turned off the alarm sounder so hadn't noticed - the alarm circuit must use that fuse well. So inconclusive for fault so far. Of course it could be just that the battery has reached the end of its life.
 
Checked for anything drawing current today by bridging each fuse in turn with a multimeter. When I bridged the 'radio' fuse I got a fluctuating current - that left me and my neighbour somewhat bemused until his 8 year old some pointed out the flashing indicators. Doh! I'd turned off the alarm sounder so hadn't noticed - the alarm circuit must use that fuse well. So inconclusive for fault so far. Of course it could be just that the battery has reached the end of its life.
 

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