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900 battery warning light

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’89 SAAB 900 Auto sedan Battery warning light

Over the last couple of years I’ve been trying to trace an irritating fault that never seems to get any worse and never causes any distress apart from on two occasions finding the battery flat after a short period of being idle.

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During a longer than normal drive, say 50 miles plus, the battery warning light would start glowing just enough to make it’s presence known. The intensity of the light would only vary slightly whilst driving, sometimes extinguishing completely.

My first thoughts turned to the brushes within the alternator as I doubt that they have been looked at since the car was built 31 years ago. I should point out that the car has only covered just under 60k. miles. Trying to remove the alternator from the engine (B202) proved too much for me, no access and Allen key bolts that would not shift. So an “on bench” inspection was thwarted right from the start. Obviously the drive belts had been checked right from the start even to replacing them but to no avail.

After the flat battery instances it was thought that there may be a faulty cell within it so a new battery was tried and this seemed to cure it for a little while. But no, on another run the glowing warning light returned.

After a few years of this I learned to live with it, now and again when going for a short break packing a spare fully charged battery.

During the lockdown period thoughts again returned to this problem. All the main electrical connections were cleaned and checked but before starting this job I removed the battery from the car and put it on the bench connected to the charger. With the two battery terminal clamps now free I cleaned the inside faces which were quite well coated in years of grime. Whenever these terminals have been removed I have always given them a cursory wipe over but this time used a small wire brush and degreasing agent and brought them up to a fine shine,at the same time the clamp jaws were carefully prized apart as over the years with constant tightening of the holding bolts the clamps were getting smaller and not fully sitting down on the battery terminals.The battery terminals were then given the same thorough cleaning. After that a light smeer of petroleum jelly was applied to the terminals and all reconnected.

This all happened a few days before a family reunion 60 miles away. So with a keen eye on the warning lights we set off and all was well, no sign of any malfunction. I would like to have thought that was the last of the dimly glowing light.

But no, on a short journey across town a couple of weeks later the dim light re-appeared so it is back to square one.

I shall now have a concerted try at removing the alternator and looking at the brush-gear.

A few weeks have passed since the last sentence was written, things like medical procedures and lockdowns having interfered with life.

However when the time came to investigate the removal of the alternator again I completely failed, even trying to remove the brush holder together with the diode defeated me.In this case it would seem that a previous attempt in the past had also failed as one of the brass 2BA screw heads had been damaged so was I was not able to get a good grip on it. As for the alternator I shall have to fashion a special tool to attack the three holding bolts on the alternator mounting bracket. Clayton Spears

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