MDamen

I already searched on alternator light and got a lot of descriptions of alternator and belt failure. My problem is different. The alternator light does not come on when the engine is running, it comes on after I turn the engine off and stays on. I haven't been able to troubleshoot the charging system yet because the next time I went to start the car it was dead. No starter, no click. nothing. Battery voltage was down around 11 volts. Took the battery out and charged it overnight. Haven't had time to put it back in yet. Plan to put the battery in, start it up and check voltage with the car running. Checked belts and they are worn, but working. Battery ground strap is clean and tight.

I recall that the alternator light compares the alternator output voltage to the battery voltage and will go on if alternator is putting out less voltage than the battery. I have never seen one stay on after the car is turned off. Any ideas?

g_murray

A common "battery drainer" is the small fan at the back of the CCU (climate control unit) NOT turning off after the car has been shut off. (Sometimes it will stay on for a couple of minutes after shutdown - esp. if the engine is hot - coz it turns on/off the engine cooling fan -- but it DOES eventually totally stop.)

Often, if the CCU goes 'bad' the motor/fan at the back of the unit, as said, stays on, and on and on. This will deplete a battery in no time at all. I would suggest, the next time you go drive the car or have the engine on for a few mins., that you switch off the engine and then put your ear (or a stethescope) to the CCU and listen. You have to be in a quiet area to hear! It'll be a light whirring/buzzing sound - barely audible - but still discernable. If the 'sound' is still there after 15 mins -- you have found your culprit.

Gerry

JasonF

Bear in mind that the CCU fan will stay on for as long as 25 minutes after you turn off the engine. My current 993 CCU fan will run that long. My old 993 did the same...but they do turn off eventually.

MDamen

I charged up the battery and got it started. The alternator puts out less than 13 volts when the engine is revved. I think there is something bad in the alternator or voltage regulator.

Edward

You should be getting around 14v (+/- .4v) with RPMs above, say, 2K. The volt reg is built into your alternator. Address the issue ASAP as a bad battery OR bad alternator has a nasty habit of ruining the other otherwise good piece. Replace both and see where you are.

Edward

Garth S

The battery is always 'hot' to the alternator B+ post - 12v output: if a stator plate diode has failed open, the alternator will drain the battery to ground .... and fail to produce the ~14V at speeds above idle. A blown regulator can also do this .... regardless, time to check out the alt is my guess.

MDamen

I suspect a blown diode or other short in the regulator or alternaor which is causing the alternator light to come on when the car is off. I've orderd a new (rebuilt) alternator from Pelican and will not be driving the car until I can get it installed. I've already seen plenty of DIY guides for the alternator install, so should not be a big problem.