944 Battery Drain

[Roger944]

My 1984 944 likes to drain it's fully charged battery in 3 days. I have checked the drain from the battery with everything switched off and I get 0.165 amps on the Fluke meter. I have pulled all the fuses, disconnected the alarm, if it's got a connector I have dis-connected it and still I get a 0.165 amp drain. Needless to say what hair I have left is gradually getting pulled out. Anybody got any ideas on what the battery drain should be at rest with everything switched off and what could be the possible cause of the drain. All the obvious things have been checked as far as I am aware.

Thanks in advance, Roger944.

 

[ukmastiff]

I dont have an 84 944 to compare or I would for you but a quick calculation tells me your battery would be flat at that rate in around 2 weeks not 3 days if its a 70 amp battery. Are you sure your battery is charging fully and also holding the charge. How old is this battery and is it a decent one.
Maybe its not a battery drain as such just a knackered battery ( technical term lol) . The recent temperatures have been very hard on poor batteries and will show the weekness in even a mediocre one. I'm thinking you know a bit about electronics anyway as you have a 'Fluke' , I have a rather nice one from my ex lecie engineer days []

 

[robwright]

Immobilisers and alarms cause a constant drain on the battery and your figure for current drain doesn't seem much at all. It may well be your battery. How old is it? Have you had it discharge tested? I would disconnect the terminals of the battery and repeat the exercise after three days. Even better see if you can borrow another battery and try that after three days. batteries especially old ones do not perform as well in the cold either.

 

[cococola]

try removing the heated rear window relay,I had the same trouble and the relay stuck intermittently.It was fine once I replaced it.

 

[rcsalmons]

Has it got a Porsche immobiliser? If so you will find 2 fuses under the dash in the steering wheel area.
Pull them and measure the current.

Rich

 

[Diver944]

Another common thing to check is if the glovebox light is switching off properly. Open the glovebox and feel if the bulb is already hot (I know it should be off with the fuses out but stranger things have happened [8|])

 

[pauljmcnulty]

I've seen a 944 with three alarms and two immobilisers, all fitted without removing the previous ones. Scary how quickly it drains a battery.

I'm with the others, though. The cars are very sensitive to a decent battery so if it's more than a couple of years old worth replacing. I've had rather a lot of calls over the last six weeks about cars that won't start, and almost every one had a baterry older than the owner could remember. []

 

[sulzeruk]

You could have a diode that has gone open circuit, try disconnecting the alternator, I have seen this on quite a few cars.
Alasdair

 

[944 man]

Id suggest checking each circuit on both fuse boards, with a mulitmeter, when everythings 'off'. Youre only going to find it if you know where to look.

 

[zcacogp]

Not sure if you have one on that early a car, but check the battery terminal post in the engine bay. I have seen those go bad and leak current to earth on a 928 (and it's the same part on a 944).


Oli.

 

[Roger944]

Hi Guys, Thanks for all the comments, a bit more from myself.
I have had the car for about 10 years now and have had to replace the battery about every 2 years as the first cell next to the positive terminal always seems to die - i.e. no bubbling etc, had this confirmed by a specialist too. Anyway the battery in the car at the moment is about 5 months old, fairly decent one too, well you would have thought so from the price. Over the years I have spent loads on batteries and bought cheaper ones too. Seem to have the same issue with all of them. The car is left for 2 weeks at a time as I work away alot. I have previously used trickle chargers but I think that these "cook" the battery after constant use. I am using a CTEK unit at the moment, which does seem to do the job when it has a mind too!!!
Right so I will soon be disconecting the alternator, then pulling the dash out to try and find the drain.
Anybody got any figures on what drain I should expect??

Thanks, Roger944.

 

[944 man]

ORIGINAL: zcacogp

Not sure if you have one on that early a car, but check the battery terminal post in the engine bay. I have seen those go bad and leak current to earth on a 928 (and it's the same part on a 944).


Oli.

Its only the later series two cars that have this: the ones who dont have a mechanically key-operated hatch lock.

How/where does this happen Oli, as my later car has one and Ive always been wary of them...

 

[944 man]

I don't think that you'll need to remove the dash Roger - there's very little electrical gubbins behind there on early cars, other than the ECU. Early cars have two fuse boxes one by the passengers left foot and the other above their shin. If you sit in the car with everything closed/turned off as you would normally leave it parked, you can then (more easily said than done: I have laid the passenger seat flat and lowered the rear seat back then laid on my back head first into the foot-well before!) take a reading across every fuse terminal. This way you should be able to identify which circuit is draining the battery; assuming that it isnt the alternator or another leak to earth as others have suggested. Even if it is you'll be able to establish this by ruling out all of the fused circuits.

 

[Roger944]

Yes, had fun with the fuse boxes before, think I'll take the passenger seat out to make life easier. Such a shame as I love driving the car, but after 2 weeks away I just don't trust it to start so it gets left until I can build up the enthusiasm again.

 

[944 man]

Id try not to take the seat out, because early cars use 10mm hex headed M6 bolts and theyre tricky (if you cant get a socket on then try sliding it in from the front of the channel, where its flared). The real issue ,though is the captives in the floor: they frequently come free and its an absolute b*stard of a job pinning them, so that you can bolt the set back in securely. If you do take them out then Id replace the fixings with M6 cap headed bolts, similar to those used in series two cars.

Simon

 

[zcacogp]

ORIGINAL: 944 man
Its only the later series two cars that have this: the ones who dont have a mechanically key-operated hatch lock.

How/where does this happen Oli, as my later car has one and Ive always been wary of them...

Simon,

Thanks.

I've only seen it once, on a 928S2 which had a battery draining problem. Not related to alarms, immobilisers or anything else that could be traced through the fusebox.

We ended up testing for current flow at various points of the live cable as it went along the car (battery in the boot, like the later 944's - as I'm sure you know). I unscrewed the live terminal post under the bonnet to get to the ring terminals underneath it, and the current drain dropped off immediately. I never did find an explanation for it as the terminal didn't appear to be shorting on the metalwork underneath (there was insulation there, and the current drain was too low for a dead short - although thinking about it the insulation could have been breaking down). However I cleaned it all up and re-assembled and all was well (and remains so to this day).

The whole car was a bit odd. Electrical maladies galore. Bought as a near basket-case for restoration. We spent a LOT of time chasing small electrical problems, and now it is all as it should be. Snag is that the owner now has no money left to tax and insure it, and it's SORN in his garage!


Oli.