85 300 SD sometimes won't start

I replaced the alternator not long ago, and had the battery replaced just about 4 or 5 months ago. Every once in a while (not even every day) it fails
to start. It will click once (sounds like a relay....I guess it has a "bendix" solenoid for the starter?), and that is all...starter is not even being energized. Jump it from another car, and it will start immediately, and the first time cranked. I checked the alternator output, it is 14 volts. Haven't checked amps yet. When the starting has failed, the battery voltage is still reading 12.5 volts, which I think is normal. Is the bendix solenoid going out possibly? In such a way that it sometimes doesn't pull in to energize the starter at 12.5 v. , but does work at abt. 14 v.?
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It's your starter.

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little more info: checked the charge amperage to the battery, it is abt 8.5 amps 5 min after start, no lights or A/C on.
If indeed it is the starter.....seems like it could be the bendix relay ON the starter, not the starter itself....www.thebenzbins.com has one for 130.00 plus 60.00 core value. Is this a good price? They do not show a separate bendix relay, the bendix comes as a part of the starter. I assume you can't get JUST a bendix relay, then? thanks, Jim

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When the starter does nothing hit/tap the starter with a 2x4 or hammer. If it then starts the problem is definitely there.
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If it click, the selenoid is good.. the starter motor is bad... usually due to bad brushes. You need to change the starter.
Autozone has starter for $110 with lifetime warranty on special order... I'd go with that instead... due to lifetime warranty.
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Can someone give me a source for purchasing new brushes? Of course, I am not running a repair business, I'm just a car owner, so it has to be a supplier that will sell retail to the public.

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It is not just the brushes.. sometime the bearings are shot too... and then there is a possibility that the stator is cracked or unusable... Just buy a rebuilt one with lifetime warranty.
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starter are fine. For example, do you try to turn the key more than once? If so, do you get only a solenoid type click every time or just once? When you jump from another battery do you jump just to the battery terminals? Turn on your headlights, interior lights, or something else electrical that you can observe when you turn the key and get the ignition click. If your headlights (or whatever) ceases to work at this point your problem is probably nothing more than loose terminals on your battery. This would be my first guess since you say the car starts when you jump from another battery. Doing so will make current available from the other battery directly to the cable terminals at the battery, thus providing adequate starting current even if you have no contact between your battery terminals and the cable connections. Once the car is running you would normally have enough current to make the connection at the battery terminals, although certainly not a good one. If this doesnt work respond back. Well all try to go from there. Also, make sure youre very specific about what you have tried. But clean those terminals good before trying anything else.
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