I am an owner of a 1990 944 S2 cabrio. My situation is that when the battery is freshly charged (a full charge) the motor turns over (a little slow) and starts great. The issue is when I drive the car or let it sit I and go back to start it, the motor is very slow and the battery quits. (seems to discharging the battery all the time) I have to go and fully charge the battery to be able to start it again. There is a new battery. Should I be looking at the alternator? The gauge in the car doesn't move very much, 11 on start to 12.5 on run.
Kinda confused and afraid of the cost of analysis at the porsche dealer.
Jim

 

Have you tested the load on the battery with the car off - It should draw very little - mine does 55mA. If it draws little, then you can look further. I had a similar problem, but it was the battery. Well, I guess that's what the shop who tested it said. I just replaced it so I won't know for awhile whether it discharges again.

 

I just saw the post about the relay for the windows being bad and stuck on so I need to say if it draws alot more than 50 mA, you need to look further also, but you know it's not the alternator!

 

Thanks, I am going to get into it this weekend.

 

Well, It has been a while, but while I was doing the clutch change, I found that the brand new battery was bad.. I looked in the glove compartment and found the warranty card. GUESS WHAT???? This is the second battery in my car. Looks as the previous owner had put in a new battery in April 04. got a free replacement battery in March 05. I purchased the car in April 05. Now it is March 06 and battery is bad (shorted out)... Do not know if it is a battery problem (bad luck) or a system problem (draining charge or shorting).
If it is the battery... They were Exide 41-60 Battery from NTB.

http://www.ntb.com/batteries.do

It is now a Interstate Battery MTP-91

http://www.ibsa.com/estore/search.as...CRank%7C1&js=1

I figure that I needed to change batteries, besides the Interstate says they have 700 CCA and the Exide is 600 CCA. and We all know more is better .

As for the charging system. Draw in the car was told that is not even an amp (probably the computer, alarm and stereo) and when running is charging at 13.5-14 amps. When I turn on the lights (heavy draw) guage drops below 12 amps but recovers and moves to 13.5-14. So I am assuming (bad thing to do ) that the alternator is doing it's job. So I am going to drive it and see what happens (I will keep my cell phone with me just in case)

NOW, all we need is some nice weather to drop the top and go...