Porsche Enthusiasts Club Forum

Hi all. About a month ago I put in a new battery and today the car would not start. I replaced the battery after the old one went flat a couple of times within a few weeks. I guess I could be looking at a new alternator. Do they die suddenly or do they gradually give up? Seems like mine is gradually giving up. Moday was the last time I drove it and it was a fairly long drive, had the lights on on the way home.

Edit:
Just had a look online found this

http://cgi.ebay.co.uk/Porsche-944-brush ... 3cb00f4265

Anyone replaced one on an S2. Can you do it from the bonnet?

What's the reading across the battery terminals when the cars running? That'll tell you if the alternators charging or not - I had mine rebuilt by a local technician for £37 I think it was - that was for new bearings and voltage regulator. It's a bit of a mare to get off if the bolt is seized in there like mine was but that only coct £25 to have pressed out then I bought a new one off ebay it's 130mm x 10mm shoulder bolt. (I wrote about it on my blog)

Currently I have the battery out charging so I cant test it. I just went out to maplin and picked up a multimeter for £4.99. Might have been cheaper to do that first time around rather than replace a good battery. Never used a multimeter before but have just looked around the web. I believe I need to set it to DC then do the check with the engine on. The site says 13.5 - 14.5 indicates the alternator is healthy anything below 12 and it won't charge. Does that sound right?

Could also be a battery drain problem - check usual suspects, glovebox light etc.

Rich

Yes Rich I had wondered if perhaps the battery is being drained. I read that if I take off the positive lead then I can use the multimeter to connect and get an amp reading. I will post the results of both tests tomorrow.

Mike

Depends what multimeter you bought from Maplins but I would check the current rating of the meter and leads before connecting it in series with the battery, you could find yourself with a piece of melted plastic or worse.

Usual suspects for draining are alarm/immobiliser, glove box light, alternator (diode pack).

Bad charging not always down to the alternator could more likely be a bad earth either at the battery to the bodywork or one of the many earths under the bonnet.

Like you said easiest test for charging is with the battery connected and the car running put your meter +ve to +ve and -ve to -ve (in parallel) and check the voltage as you said the battery should have just over 12vdc with the motor off and 13.5 - 14vdc with it running any more than 15vdc is usually a sign of overcharging and points to a faulty alternator (also screws your battery).

Like mentioned earlier if it is the alternator I would get it off the car (not so easy) and take it to a Bosch service center or your local auto electrician to get checked and repaired.

Take a look at the link below taken from PCGB website but it details a comprehensive list of parts from other vehicles which fit on 944s I think there is some alternator information there.
http://www.alanara.fi/Possu/ENosat.html

Ok just put the battery back after charging over night. The DC reading with the engine off is 13v. Does that seem a little high, could it be because it has been on the charger? With the engine on on idle I get 14.1. I will get the girlfriend to rev the engine a bit and I will take new readings. Also going for a drive so will check again with the engine off.

14.25 with a bit of revs.

14.25 with low revs seems OK I would increase the revs to over 2K to see if the voltage increases to around 14.5, it should not go up to 15 or above this is a sign of a dodgy alternator. So again 14.25 allowing for volt meter accuracy is ok normally around 13.5-14.5 on my interior volt meter in the car and just over 14vdc with a meter in parallel with the battery and car running.

You could set up to read the voltage with the car running and in turn switch on the electrical items i.e. lights until you get all of them on then the voltage may drop to around 13vdc at idle but should rise to 13.5-14 when the engine is revved over say 2k rpm.

If this is not the case the alternator may be on its way out or more lilkely you have a bad earth somewhere in the system.

Thanks David I will give it another go with higher revs and I will also try with lights on as well and post the results. The results that I posted were at 2k with no electrics on.