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Discussion Starter · #1 · (Edited)
I'd heard this done before. Anyone on here do it? The commem's battery is 5 years old and pretty much not holding its charge anymore, but also the in-dash voltmeter was only registering about 12.5 volts. Time for a new alt, but thinking of going to the larger output.

Doable? Any tricks I need to do to make it work in a 900?
 

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Sounds like your Brushes are worn out. If you want to see the Voltage on your Dash Gauge to say what ever you want get the old Volvo 26o adjustable regulator kit. I Actually remember working on those cars. The kit works, the 260 just happen to have come with them stock. Link http://www.davebarton.com/AdjustableVoltage.html
 

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Discussion Starter · #3 ·
How does that thing work? Does it drop right into the Saab/Bosch alternator?
 

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Your Brush holder is little more than two brushes and a Simple transinstor to regulate output voltage. This unit goes in place of the stock brush holder "Regulator" and gives you an externaly controled Voltage regulator. You set the output to what ever you want.
 

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Discussion Starter · #5 ·
Yah, I know about the stock VR and brushes (I've changed countless ones over the years). Cool to know about this thing. I think I'll give it a try.
 

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I put the alternator for a '91 9K Turbo (115 amps) in my '88 SPG years ago. I think the only oddball thing I had to do was ground the alternator case to the block.
 

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Discussion Starter · #8 · (Edited)
Your Brush holder is little more than two brushes and a Simple transinstor to regulate output voltage. This unit goes in place of the stock brush holder "Regulator" and gives you an externaly controled Voltage regulator. You set the output to what ever you want.
Off topic a bit, but I was in the area yesterday(Finksburg) returning from a client meeting, looked for your shop wanted to drop in, say "hi". Not sure which building on Industrial was yours though, and couldn't find you (looked for signs, or address numbers).

Anywho, thanks for the tip on the adjustible/remote VR.

BTW, you know you haven't driven your c900 in a while when there are spiderwebs on the wheels.... <sigh>
 

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Discussion Starter · #10 · (Edited)
Jeezus Effiing KEEERIST!!! I do not remember the VR being this inaccessible.... I was hoping I wouldn't have to pull the alternator out to get to it. Bought the remote adjustible VR from Dave Barton and got it in yesterday, was hoping to install it today. One mounting screw for the VR is sitting behind the oil filter mount/oil pressure switch. Can't get to it--not even with a ratcheing 90* screwdriver...

Looks like the Alternaor is coming out. Crap.
 

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I have heard of people installing alternators from 9000s without any trouble (they are higher output). I believe the member breakin5speeds or breaking5speeds had mentioned it on SC a few times if you wind up searching for that route.

I'm too late obviously, but did you make sure that the battery and ground connections everywhere are 100% clean? I had a corroded terminal that prevented the battery from charging properly, and it got so bad that I literally went about a mile down a hill, in gear, and could not get the engine going. 3 minutes later with a round file and sandpaper, and it started right up.
 

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Discussion Starter · #12 ·
Hey, man. Yeah, terminals are clean. Pristine, in fact. Did some research into both batteries as well as alternators/VR's: Batteries are really only good for about 4-5 years. My battery was installed in 2005.

New battery now installed, and rechecked voltage at the battery with the engine off, engine idling, at 1500 RPM both unloaded (no power devices on) and loaded (AC, headlights, stereo all on). Under full load, voltage drops down to 10 volts.

Ummm. Not good. So definitely the VR. Got the adjustible one, just didn't have the energy to tackle it this weekend.

I did buy a 90* screwdriver as mentioned above. It's still so tight, I can't get the head in there to unscrew the VR. Going to have to pull the alternator, or at the very least get it loose enough on the mounts to shift the alt over a bit to fit the driver in there.

Kinda committed to the VR kit now that I've made the purchase (does anyone know if the voltage regulator on the 80 amp alt also fits the 115 amp alternator?)...

Just don't have much of a window to work on the car now with the kids. Get to it when I get to it I suppose. Just don't want to waste the entire summer not driving it...

<<sigh>>
 

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Discussion Starter · #14 ·
Yup.
 

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Discussion Starter · #15 ·
Success at last. Got the brush assembly in -- a true biotch to get in there. Remote adjustible VR works like a champ. 14.3 volts at about 1900 RPM, and down to about 13.3volts under load.

I knew headlights were a hit, but never really realized out much of a hit. Anyway, great little kit. Thanks Harvey for suggesting this little trick piece.
 

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OK...I tried to use the remote VR and couldn't get it to fire up...tried it twice w/no luck. The supplier can't figure it out either. I think my alt has a worn out slip ring set [ I get quite a bi tof drop off with everything on] so I am thinking of installing the 9000 alt w/115 amps. Should be better when all the stuff is on.

When fitting the 900 alternator I know the pully needs to be swapped...what else is involved?
 

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Success at last. Got the brush assembly in -- a true biotch to get in there. Remote adjustible VR works like a champ. 14.3 volts at about 1900 RPM, and down to about 13.3volts under load.

I knew headlights were a hit, but never really realized out much of a hit. Anyway, great little kit. Thanks Harvey for suggesting this little trick piece.
There should be no need at all to go with an adjustable vreg as the standard output range is specified as 13.5 to 14.5 volts under all situations once the vreg has become active. It should not matter what revs the engine is doing.

Remember too that a volt gauge in the dash will, unless it connects direct to the unswitched 'terminal 30' circuit, never display the battery terminal voltage as the voltage on the switched circuits will always be less due to the voltage drops at the ignition switch and elsewhere.

In my 81 turbo car, for example, when the battery has about 12.5 volts at the terminals, the volt gauge in the dash (connected to the terminal 15 circuit) measures about 10.5 volts. When the vreg becomes active after starting and the engine revving above about 1000 rpm, the battery voltage is usually between 13.5 and 13.9, with the volt meter in the dash showing just on 12 volts.

Craig.
 

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Typically in order to easily change the alternator brush / VR pack on a turbo 900, you need to pull the pressure sender & one of the oil cooler lines. Once that's done you can fairly easily replace the brush pack in about 30 seconds with standard screwdrivers.

Also, FYI unless you have some sort of high power stereo or an electric heater in the car the standard output Bosch alternator will work just fine. These cars do not have alll that much fancy electronic gadgetry. Now... Upgrading it is just as easy as replacing the unit, so if you have a 115 amp 9000 unit, no reason not to use it. If you were order a replacement unit however, the 115 is significantly more expensive and IMO, not worth it.
 
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