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Discussion Starter · #1 ·
When I start the car and let it warm up a bit the voltage reads 13.5. As I drive I look at it and it gets down to about 12.5, and when I am parked and the engine is idle, it can go all the way down to 12.0-12.1,12.2 it fluctuates until I start driving and then it can go all the way back to 13.0.
Is this an indication of something failing? I am going to clean the battery terminals tonight and see if that helps, any ideas.
Thanks
 

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Probably your alternator is failing. The diode pack ( regulator) is likely failing. Possibly your accessory drive belt is not tensioning which means the idler/tensioner may be failing.
 

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Voltage regulator assembly at Rock Auto - $68:





http://www.rockauto.com/catalog/moreinfo.php?pk=445582

To replace a regulator remove the black cover (3 phillips screws, and disengage the 3 pry tabs on the side of the cover).
Carefully lift and remove the cover, set it aside.​




You'll see that the voltage regulator is secured by 2 phillips screws.

Remove them and set aside, and carefully lift up the old regulator and place it someplace secure (if you will reuse it







You can do the regulator R&R without pulling the alternator. Just reach down behind the intake manifold and remove the 2 wires and the plastic cap, release the regulator screws. Pull the old regulator,brush assembly out and pop in the new one.

 

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Thanks chengny. The regulator approaches the cost of a remanufactured unit minus core, which will probably have new bearings as well.
 

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Thats because modern alternators are built to last. Generally it is the regulator pack that dies usually due to heat. Note that the regulator assembly comes complete with the other consumable item: the brushes.

The bearing will wear if the drive belt tension is too high, otherwise those alternator bearings last a looooong time.

Touch wood but I have never replaced an alternator on a European or Japanese built car. My Alfa has a 21 year old Bosch alternator. 209,000 km.
 

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Discussion Starter · #9 ·
My voltage reg assem should be coming today, I am going to assume that i need to disconnect both the pos and neg cable attached to the battery, right?
 

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Just the pulling the negative is okay.

When you get the old regulator out compare the length of the brushes with the new one. The old brushes will be little stubs that barely make contact with the slip rings. That is the cause of inconsistent charging.

Also notice that the outer brush will be shorter than the inner. That is due to it's proximity to the (heat generated by) the rotor bearing.
 

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Discussion Starter · #11 ·
Cool thanks Chengny. I tried to just pull the cover off without taking the alt out, but the fit is tight, so it didn't work, but I'll try again.
 

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Discussion Starter · #13 ·
I did , but I think the back side of the cylinder case in is the way. I was thinking of maybe just loosening the alt, pulling it out just enough so I can pull the back cover off, doing it that way. What do you think?
 

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Yeah - there is a wireway bolted to the engine block under the intake manifold that makes it difficult to remove the cover. You'll never move that. So if you can't squeeze/twist the cover by the wireway, you'll need to flop the alternator back.

Gets more involved.

Remove wheel arch trim and rear half of inner fender

Release tension on the auxiliary belt (use a locking tool on the tensioner if you have one) and take belt off alternator

Completely remove the upper alternator mounting bolt and loosen the lower. That should allow you to pry the alternator back towards the firewall and provide sufficient clearance to do the regulator.

 
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