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Re: Cooling Elec Fan, Headlights & Idle with 100amp Alterat Posted by eric in vermont [Email]  (#2058) [Profile/Gallery]
(more from eric in vermont) on Thu, 13 Aug 2015 16:58:41
In Reply to: Cooling Elec Fan, Headlights & Idle with 100amp Alterat, 88SPGClone1, Tue, 11 Aug 2015 20:06:09 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Wow. Not a nice problem.
Have you measured voltage when this problem occurs? I would recommend measuring the voltage directly at the alternator to see what it's doing. From the B+ terminal to the alternator case. If that voltage is good, IE is around 13 to 14 VDC or so and rock steady, then the problem is elsewhere. Like a bad ground connection which can dissipate a lot of power.
So if your alternator output is good, then try to find the voltage drop.
Another method is to try and find out what is sucking the power and dragging down the alternator. You can do this by removing fuses- but to me, if its dragging down a 100A source, then the fuse would blow! The other item that can draw a lot of power is a motor, like your starter motor. If partially failed, it can draw a ton of current even when not turning. So it could be loading down your alternator such that the majority of power is being dissipated in that, and when you start turning on accessories, the alternator can't keep up. Carefully lay a hand on it to feel if it's hot. Or you can get one of those clamp on ammeters and go wire by wire to see where the power draw is.
I have a Saab 900 alternator on two of my VSaabs (about 85A rating) and they are both rock solid. Like 13.82 VDC and it doesn't change 10 millivolts over the full rev range of the motor.
So in sum, these Saab electric systems are pretty simple. You have one of the following:
1) A bad connection like a major ground.
2) A component sucking a ton of power when it shouldn't- and the starter motor is the one that comes to mind.
3) You have two bad alternators in a row, however unlikely.
eric in vermont
posted by 209.99.195...
, Thu, 13 Aug 2015 16:58:41 <-- Viewing This Message, Fri, 14 Aug 2015 10:59:40
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