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Flat battery again

944cabby

944cabby

New member
Guys, for the past 5 weeks i've been working away from home - 4 to 5 days plus at a time and every time i've got back and gone to start the cab the battery has been completely flat - no alarm, etc nothing.
I initially thought the battery was duff after charging it a couple of times so i bought a new one 3 weeks back - she turned over much better - really quickly, but again now after 6 days without starting her she's completely flat again.
Could it be the alternator isn't charging properly when it's being driven (the guage is between 12 to 13) or is it likely to be another issue?
What do you reckon chaps?
 
What is your voltmeter reading with just the ignition on, and then with the engine running? If it's higher (circa 13V) with the engine running then that's a fair indication the alternator is doing its job.

Check for current drain using the fuse box. It helps to have 2 people for this as one of you needs to hold an ammeter inline on the negative lead for the battery (rather than positive so you don't short out on the metalwork) whilst the other pulls each fuse in turn starting with the most likely candidates first (radio, central locking etc).

There will be some current draw naturally and for what it's worth mine is 3mA. If it's significantly more that shows you have a problem and pinning down which system it is located in by pulling the fuses will give you a good start in tracing the fault.
 
I remember reading something similar a while back, turned out to be the glove compartment light - the switch that turns it off had snapped but obviously you couldnt tell [:D]
Id say its best to try simple things like that before going after more expensive things like alternators. Would bad grounding cause something like this? i think i read that could cause the same problem??
 
Saw this on the Cab we had at MPH '06. Where the hood folds it had detatched two small black wires that were draining power, somewhere around the top of the rear seat IIRC. Somewhere to look, sorry I can't be more help!
 
I had a similar thing with my old 944S.
The ignition switch was (intermittently) "making" when the car was parked and locked. The interior passenger compartment ventilation fans would then come on and flatten the batttery in no time.

New switch contacts cured it (thanks GT-One [8D] )
 
Thanks all for the excellent replies.The hood sounds interesting as i've been leaving it down recently whilst it's locked in the garage, perhaps there's a trapped wire.
Thanks all!!
 
Admittedly mine is a Series 1, but I was faced with the same problem a few years ago and I traced it to the coolant fan thermo switch mounted in one of the radiator end tanks. In the "cold" (no fan) state it was allowing current to dissipate through the fan motor, but not enough current to rotate the fan.

I'm not sure how confident you are with automobile electrics, however, one method in determining where the power is "leaking away" would be to use a multimeter on, say a 10 amp current setting, with the ignition off and key removed. Then remove one fuse at a time and place the meter accross the fuse terminals to see how much, if any, that particular circuit is demanding.
 
Before I fitted a new alternator a few months back due to a noisy bearing, the dash gauge only ever used to show 12 volts, but since the change it rarely drops much below 14 volts.

I would check the alternator output to confirm it is within limits.

Good luck
 
Looks like this could have been the problem - i charged the battery and fitted it this morning, had a nose around and noticed some light coming from the glove compartment as Alexw mentioned.
Thanks again, hopefully she'll fire up when i return home next week.
 
Glove compartment light swithc sems like a weakness. Mine was draining the battery and so far I have resolved the problem by taking out the bulb... Must get round to fixing it properly. Its worth checking!
 
Well, tried to start her after 4 days and she was completely dead again - no light on the immobiliser, nothing.Tried to start her from jump leads but all she did was constantly "click" and try to turn over but wouldn't fire up.
Checked the glove compartment light again and removed the bulb and within a very short time she fired up fine.Annnoying or what!
 
It's funny you should bring this back up today as I was only thinking about this topic earlier on.

I thought my car was pretty spot on when it came to electrical drain, and indeed it was until yesterday but for some reason my glovebox light decided to jam on too!

I've taken the bulb out and shall have a proper look tonight, I'm just glad I noticed.
 
My glovebox light crumbled to bits when I removed it to get to the heater clip. I just sealed up the wires and figured I could live without a light in there, glad I did now!
 
Well, i left the hood up this time and it still did it.Although i went for a run this afternoon and she was starting up fine after, so i'll see what she starts like tomorrow.Fingers crossed.
 
I had a problem with mine where one of the micro switches wasn't switching in the down position. This meant the motor was still trying to run and the battery drained very quickly.
 
ORIGINAL: chrisdenton

I had a problem with mine where one of the micro switches wasn't switching in the down position. This meant the motor was still trying to run and the battery drained very quickly.
Click to expand...
Could you hear the motor running?
 
No, the motor is trying but it cant go anywhere as the roof was fully down. I proved the point by making and breaking one of the microswitches above the windscreen while measuring the current drawn from the battery. I cant remember the exact numbers but it was drawing something like 2 amps and dropped down to milliamps with the switch pressed.
 
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