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Old 4th November 2004
Grant Grant is offline
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Join Date: Apr 2004                                                
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Default Alternator output

I have a 1991 2.1L NA 900. Over the summer, with the help of my friend John at SAAB Savior, I installed some of the VDO guages in the center console slot....oil pressure, oil temp(completely useless gauge it seems, but it looks cool) and voltmeter. The voltmeter came in really handy right before I left home to go back to college cause I was able to watch my alternator slowly die as the volts dropped below 12. Anyhow, I bought and installed a brand new alternator from the local auto parts store. Now my gauge reads right at 14 when I first start the car and slightly lower after she warms up. If I turn on the headlights it sits a little above 13 and when the cooling fans cycle off and on the volts might drop to 13. I don't think it ever drops below 13, but on all the other cars I have ever driven the voltmeter never really moves off of 14. Are my volt readings normal?
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Old 4th November 2004
sulloj's Avatar
sulloj sulloj is offline
Join Date: Mar 2004                                                
Location: Pine Bush NY 12566 USA
My Saabs: 2005 9.3 Linear; 1989 900 Turbo
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Default voltage readings

If you have an external volt meter, hook it up to the battery and compare with the dash gauge for accuracy.
The alternator is going to supply enough power to run the demands placed on it and keep the battery up to surface charge. You might try checking the surface charge of the battery before you start the car, then make comparisons based on the surface charge reading. The bottom line though, I think you're in good shape as long as the readings are not dropping below 12.5v
Keep in mind the voltage is moved by the amps and if the amps are not up to snuff, the voltage will drop. This is what usually kills an alternator's output! One should never replace an alternator with one that has a lower amp output than designed for the application.
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Old 5th November 2004
cdaly's Avatar
cdaly cdaly is offline
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My Saabs: '92 900LPT, '90 900i vert
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What's much more useful with the alternator is an ammeter. This will show you the state/rate of charging output from the alt. In normal running, it should be a little positive of centre, just after starting on a cold morning, with lights, demister and battery to charge, it should be well over to the right (positive). If it ever goes left (apart from starting) you're draining the battery.
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Old 5th November 2004
dakinebusa dakinebusa is offline
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Join Date: Nov 2004                                                
Location: Northern Michigan
Posts: 9

European cars generally have 13 volt regulators.
US ones run much as 14 volts.
Make sure the ground strap that connects the alternator to the block is in place and has clean connections.
13 volts at the battery with the lights on is fine.
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