SaabCentral Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
242 Posts
Discussion Starter · #1 ·
So I have just arrived home back in Newcastle after a weekend in Sydney. Car was going fine, but as soon as I left the freeway (slowing down at the end of the off ramp) the battery light came on on the dash. It remained on for the rest of my 10 km or so trip home. Didn't notice the car running any differently. The battery light is on quite dull, but all my other lights work fine at the moment.

So I opened my bonnet when I got home and had a look with the engine and ignition turned off. The alternator belts are both fine, and all the wires seem to be ok. I checked the black earth wire from the alternator to the engine and there was continuity across it, so I assume it is also fine. I turned the ignition on and have about 5 V at the green (I think it's the "field voltage" wire?) and have about 12.3 at the big red wire coming from the alternator. I noticed this joins to the power cable that runs to the starter, which in turn runs to the battery, so I guessed that this was probably battery voltage I was seeing. When I checked the battery this was about right.
When I started the car and checked the battery voltage, it had dropped to about 11.9 V.
I think all signs point to either worn brushes, or alternator windings that have burnt out. I have done some reading to see if there are any common issues other than these that could be causing it, but couldn't find anything.
I have pretty much resigned myself to pulling the alternator out, checking the brushes, and most probably needing to replace the whole alternator, but thought I'd check here first in case anyone knew anything else to check.

Now I think about it, I had an old Niva that suffered failure of the voltage regulator- what sort of system do our cars use to achieve this? Does this go wrong very often?

As always any help would be great
 

·
Registered
Joined
·
242 Posts
Discussion Starter · #2 ·
I was thinking that I could maybe remove a battery lead whilst the car is running, but wasn't sure if this could damage electronics in the car when there was a sudden change in voltage
 

·
Registered
Joined
·
441 Posts
I'll add this:
http://www.saabcentral.com/forums/showpost.php?p=274451&postcount=3

Very very handy and uncovered the fault I had with mine, just got a 2nd hand one off 16saabs :)

My battery light was dim too and at the terminals at battery was only showing battery voltage when running. What swung it was touching this field wire to an earth on the engine, light immediately went bright
 

·
Registered
Joined
·
7,033 Posts
You can get a new voltage regulator which comes with new brushes for less then $10 and swap it out in about 10 minutes.
 

·
Registered
Joined
·
978 Posts
I was thinking that I could maybe remove a battery lead whilst the car is running, but wasn't sure if this could damage electronics in the car when there was a sudden change in voltage
NEVER, EVER dis connect a battery while the engine is running. IT can and will cause a voltage spike which may damage a lot of stuff. The battery, along with its many other funtions, is kind of a spike absorber, it prevents large swings in voltage, absorbing a power surge and mitagateing a drop in output from the chargeing system.

Your problem could be caused by brushes or a failed diode or even winding in the alternator. The brushes and regulator (yes they do have a regulator, its integal to the alternator) can be changed without removeing the alternator. Those two parts come togther and are cheap to try if you don't what to go thru the complete diagoises.
Best thing to do is to take it to someone who can tell you what the problems is. A good auto electrician should be able to test on the car and give you a soild diagnoisis. You can then decide if you want to rebiuld youself (if you are confident in your abilitys) or exchange for a rebiuld, of if it just needs brushes and/or regulator.
The test should show reg set voltage, amps at idle, amps and voltage at rated speed, and whether or not all phases are generating power (diodes/stator ok). All of this can be done with the altenator on the car, and can also test the wireing and connections between the alternator and the rest of the car. Remember, the saabs alternator is electically isolated from the engine block and must have a ground wire, the same size as the output wire, to connect it to the block.
 

·
Registered
Joined
·
104 Posts
Many alt faults are repairable, so you probably don't need a new one...
...but reconditioned ones are so cheap, that you may as well just replace the whole unit - if you want to repair yours, then you car is going to be off the road for as long as it takes.
I got the US $88 one from these guys
http://www.ebay.com/sch/bnrparts/m.html?_nkw=SAAB%20900%20Alternator and it did the job for me !

Note : Mine came with the single pulley, but it was a simple job to swap the dual-pulley from my dying one.
 

·
Registered
Joined
·
8,923 Posts
As Nomgle says, check out the price of a re-manned alt before you go too deep. They can be quite reasonable.
 

·
Registered
Joined
·
3,720 Posts
RE: the remanufactured alternators. One caveat- make sure that your model/part number is what you are getting. One of my 83's got a remanufactured one and it turned out to be for the later years. Difference is in the diameter and thickness of the adjuster mounting. Had to improvise an adjuster for it to work as I have no spares of that year available. Pulleys may or may not be included, and if they are, are part of the core charge. So if you swap pulleys, include the removed one with the core.
 

·
Registered
Joined
·
242 Posts
Discussion Starter · #11 · (Edited)
So I got my alternators brushes out, and think they are looking a bit on the worn down side, and may not be contacting the slip rings sufficiently. Anyone with an eye for small carbon blocks know if these ones look problematic?
 

·
Registered
Joined
·
8,923 Posts
So I got my alternators brushes out, and think they are looking a bit on the worn down side, and may not be contacting the slip rings sufficiently. Anyone with an eye for small carbon blocks know if these ones look problematic?
Does look worn. Should stick out more then that. Think you've found your problem. New brushes please. Check the brush movement in the holder to check it springs in and out freely.
 

·
Registered
Joined
·
242 Posts
Discussion Starter · #13 ·
Yeah, they both spring freely, although the shorter one has very little travel because it is so worn. Hopefully shouldn't have too much trouble picking up some new brushes, or even a new brush holder/diode part if that's all that's around
 

·
Registered
Joined
·
2,537 Posts
Most auto electricians around Newcastle will have stock of those.
I've bought them from Charlestown , Newcastle Auto Electrics and even Repco........
 

·
Registered
Joined
·
3,720 Posts
Definitely worn. Replacement should be at 5mm (measured at bottom of curve). Your voltage regulator is part of the brush assembly.
 

·
Registered
Joined
·
242 Posts
Discussion Starter · #16 ·
So, good news! Managed to the two new brushes for $15, put them in, and the alternator is once again motivating some electrons.

For the benefit of any future readers of this post with the same problem, I found it easiest to take the belts off the alternator pulley and allow it to swing as far as it can downwards. The outer screw will be easy to get at with a screwdriver, but the inside one will still be very difficult. I used a pair of vice grips to grab it and rotate it. Once it's loose you can undo it with a screwdriver on a crazy angle.
 

·
Registered
Joined
·
3,570 Posts
So I got my alternators brushes out, and think they are looking a bit on the worn down side, and may not be contacting the slip rings sufficiently. Anyone with an eye for small carbon blocks know if these ones look problematic?
Definitely worn. Brushes should be a minimum of 5 mm long where they extend out of the vreg body. Replacement voltage regs are cheap so probably not worth replacing the brushes if the vreg itself is quite old. Go for a complete new one.

Craig.
 

·
Registered
Joined
·
3,720 Posts
So, good news! Managed to the two new brushes for $15, put them in, and the alternator is once again motivating some electrons.

For the benefit of any future readers of this post with the same problem, I found it easiest to take the belts off the alternator pulley and allow it to swing as far as it can downwards. The outer screw will be easy to get at with a screwdriver, but the inside one will still be very difficult. I used a pair of vice grips to grab it and rotate it. Once it's loose you can undo it with a screwdriver on a crazy angle.
It will depend on the age of your alternator. Earlier ones use a 7(?)mm head and no phillips cut. I also use 12" phillips to remove in place, or mini ratchets and bits. Did you check for wobble in your mount bushing while you were there?
 

·
Registered
Joined
·
8,923 Posts
It will depend on the age of your alternator. Earlier ones use a 7(?)mm head and no phillips cut. I also use 12" phillips to remove in place, or mini ratchets and bits.
I think you'll find that Bosch use Pozidriv screws not Phillips, although they look similar, and on the alt they are normally no 2 Pozidriv. We haven't used Phillips head in the rest of the world for many years. The drivers are not interchangeable although may people try and bugger the heads up.
 
1 - 20 of 22 Posts
Top