I need help with this one

[IvorBankloan]

Misbehaving Boxster S

Day 1; Drove 40 miles, parked for 2 hours (everything switched off) and the battery was too flat to start the car when I returned. I rolled it to start and drove the 40 miles home but on arrival the battery was equally flat so its fair to assume I'd been running off the alternator and the battery was caput. New battery fitted and everything was back to normal.

Day 2; Brake pad warning light came on. Checked and found the front were a bit low but rears had life left in them. I ordered pads.

Day 3; ABS warning light came on quickly followed by the battery / charging light. Fitted the new front pads thinking the pad warning light would go out and hoping the ABS was linked to this circuit . . no such luck everything stayed on.

Day 5 and still trying to find the fault. I've had all ABS sensors disconnected and the light stays on. I've had all brake pads sensors disconected and the light stays on. The battery went flat again so I can safely assume it isn't charging. The battery I removed was fitted to a 944S2 cab' I have and guess what it worked and stayed working so the battery wasn't the fault with the Boxster.

I can't think of how these circuits are related but the chances of all theses faults happening in such quick scuccession is about zero. Any advice or ideas would be appreciated

[Matt Fredrikson]

Alternator 110%

Always change both alt and battery together if one fails. By driving on just your alt with a dead battery for that far you toasted it. Like I said 110% sure it will solve all you problems, most cars have the abs light plus others start to come on when the alt is toast.

[IvorBankloan]

Thanks Matt,
I did trace that and overhalled the alternator. That sorted the charge light but did nothing for the ABS warning light. There's no fault with the brake light circuit which is driectly linked to the ABS but I'm not sure if there is a fuse for the ABS system. Some kind Porsche mech took the fuse box plan last time it was with them and I hadn't noticed until now. Any idea if there is a fuse before I start pulling sensors out?

[IvorBankloan]

Hi Matt (and others) you'll need to read from the begining to make sense of it
Just for interest in case you get the same problem at some point.

The battery I though was kaput because it went flat without warning after a 40 mile drive and didn't charge after another 40 miles but the car run ok on the alternator was put on another Porsche I have and after standing for week with the alarm on started first time. The original fault wasn't the battery.

The alternator was the original problem, not the alternator being the result of running on a kaput battery. The regulator had given up but the windings were good. Incidentally the pulley wasn't free wheeling as it should so that was £50 plus the regulator and general overhaull £150 in total. Much cheaper than a new unit.

With the overhauled alternator fitted all warning lights went out except the ABS light so I went through that manually unhooking each socket and unhooking the ABS pump from its power supply. none of that put the light out so I cleaned up and refitted all 4 sockets & plugs until I came to the last one at the left rear. That was the fault and unrelated to the orginal charge, brake pad, and other lights coming on (all of whcih were caused by the alternator)
In UK the left wheels pick up more dirt then the right because thets the side in gutter all day.
So for future reference if you get a bunch of warning lights come on all at once your first check should be the alternator.