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Re: electrical glitch Posted by eric in vermont [Email]  (#2058) [Profile/Gallery]
(more from eric in vermont) on Wed, 3 Dec 2008 17:44:50
In Reply to: Re: electrical glitch, patquin  [Profile/Gallery]
, Wed, 3 Dec 2008 16:51:49
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Yes, this is exactly what to do.
When the car is off, the voltage should just be the battery voltage- about 12VDC or so. During starting, it will drop down by several volts.
Once the car starts, the alternator/regulator should take over. You should have a voltage that is relatively fixed around 13.5 or 14.0 VDC. This voltage can vary car to car, but it should be a constant voltage with engine RPM. This voltage is above the nominal battery voltage and charges it up. The alternator supplies the voltage and the regulator regulates it- keeps it at a relatively fixed value so the lights stay the same brightness no matter what the engine RPM. Usually, if the voltage is low and increases with engine speed up to a fixed point, say 14.0 VDC, then the alternator is bad and the regulator is fine- could be what you describe with your car. If the voltage rises up and up above 14 VDC, then its probably the regulator that is unable to control the voltage. (The regulator is that small silver box mounted on the passenger fender inside the engine compartment. It connects right to the alternator.)
But not always! I had a problem a couple of years ago with high voltage on one of my VSaabs- it was running around 16.5 VDC- obviously a screwed up regulator, right? After swapping in spare regulators twice, I realized it was the alternator that it had to be the alternator. I can't recall if it was a bad diode or a bad winding. I went back to the original regulator and swapped in a spare alternator. Problem fixed.
If you do have a bad alternator, its a good time to consider changing over to a Saab 900 alternator. It has twice the current output of the original (70A vs 35A) and is a bolt in replacement. It has an internal regulator, so you no longer need the external one.
Why do this? 35A is not much juice if you have added things like driving lights, an electric fan, a 400 watt killer stereo system, heated seats from a 900 or that hair curling iron so you can save time and drive to work AND curl your hair (a little known but popular option). Here's a link to show you how to swap in the 900 alternator:
http://tubbs.cc/saab/alternator_conversion.htm
eric in vermont
posted by 72.248.78...
, Wed, 3 Dec 2008 16:40:25, Wed, 3 Dec 2008 16:51:49, Wed, 3 Dec 2008 17:44:50 <-- Viewing This Message, Wed, 3 Dec 2008 20:40:46, Thu, 4 Dec 2008 03:21:31, Thu, 4 Dec 2008 09:01:55, Thu, 4 Dec 2008 11:12:55, Thu, 4 Dec 2008 12:00:06, Sun, 7 Dec 2008 10:04:28, Sat, 6 Dec 2008 05:04:39, Sat, 6 Dec 2008 21:19:24, Sun, 7 Dec 2008 06:37:47, Sun, 7 Dec 2008 09:58:13
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