89 240 Wagon---charging issue. Alternator or voltage regulator?

shutterbugpaul · Post by **shutterbugpaul** » 17 Sep 2019, 07:10

I took off the alternator and took it into a discount auto parts store to have it tested, they said it passed their test all 3 times. I reattached it, same issue. When car is on and idling, voltage reads 10.75-11.25. Shut car off and it rises to about 12v. Eventually battery will not have enough juice to start the car. What is the most likely culprit? The car has the original Bosch alternator and the outside looks very old, but the black voltage regulator on the side of it looks much newer like it's been replaced before. I would like to have this car roadtrip worthy within a week's time. Any pointers?

Thank you all kindly.

Post by **jimmy57** » 17 Sep 2019, 08:08

Does the battery light come on when the ignition is switched on but engine not started? The alternator will not charge without the warning light current flow being used to make the rotor in alternator get magnetized. If you rev engine past 3000 RPM it ill start charging without that current usually due to faint residual magnetism of the rotor. The small gauge red wire that plugs onto alternator is this wire. It should be plugged onto spade terminal marked "B+/61" on back pf alternator. If it got plugged on the "w" terminal it will not charge.
Another issue on that car can be the ground wire. The alternator mounts on rubber bushings and it must have a ground wire attached between block and one of the 5 mm studs sticking out of periphery of alternator case on back end. It needs to be a 10 gauge wire but larger is OK.

Post by **volvolugnut** » 17 Sep 2019, 12:39

If this model has the replaceable contact brushes like the earlier Volvos, then the first thing I would check is the brushes. They can wear down and make poor contact. A quick check of IPD information shows the 89 model likely has the brushes made as part of the voltage regulator. Remove 2 screws to inspect the brushes.
volvolugnut

Post by **jimmy57** » 17 Sep 2019, 19:41

The brushes on that one are part of the regulator but can be sourced separately if you want to solder them in place. It would not have passed 3 times on tester with worn out brushes and failed to charge at least for a few minutes installed on car if brushes were the problem. When the cars with this generation charging system littered the service bays at my dealer the things I listed were the usual fixes are were what was checked before the alternator itself was condemned. On ones where brushe were worn out the alternator would charge for a time, maybe 20 minutes, and then stop charging with no warning lamp lit when warning light did work. The alternator would get hot enough, expand and the brushes, being tethered by the wire leads, would no longer touch slip rings. On those the diagnosis was watch voltmeter while you reach down and put pressure inward on voltage regulator. If it started charging then it needed a voltage regulator with integrated brush set.