hey guys,

help me find the culprit. this is the 3rd Bosch alternator it has eaten in the last 13 months. the bearings are shot again. this time it is so bad that there is play on the alternator pulley if i pull it on any axis (x, y, and z).

my observations:
-the belt size and length are correct. it is a continental 21.36 x 2120.
- but even after the tensioner is 'unhooked', it is still very difficult (tight) to get the belt onto the pulleys. is this normal?
- however, when the tensioner is hooked back on, the tension seems fine. i can depress the topmost section of the belt about 1/2 inch with no problem.

the belt accessory parts for this car are expensive. spring, dampener, pulley tensioner.

clearly, something isn't right. it is unlikely to get 3 bad Bosch alternators in a row. please help if you can.

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Jennifer
90 350sdl

Just had this problem on a Ford diesel truck. The problem turned out to be one of the batterys (these trucks have 2 batterys in parallel) was defective. I actually have seen this many times on other vehicles. The battery will not take a FULL charge but will take the amperage. This truck was charging at about 90 amps but could not get the voltage up. I unhooked the bad battery and the voltage came up as it should and the amperage droped as it should. This is the type problem that normal battery testing will not find. Alternators may be able to supply a certain maxium amperage but they can't supply it for long periods of time in extreme heat. And by the way, this truck had 2 new batterys installed at the same time the first new alternator was replaced and the alternator was a Bosch reman. The alternator had already been replaced again before I got the truck. You will need to find a meter that can read voltage and at least 100 amp. These tend to be expensive (the one I use now was about $1000). See if you can find a shop that has this type of equipment and someone that knows how to use it.

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84 500 SEL (307,xxx miles)

Unfortunately, it is not so unusual to get three bad remanufactured alternators in a row. I've had it happen twice (once on a Benz, once on a VW).

That said, each of the alternators failed for different reasons (bad diode, bad voltage regulator, case screws came undone, etc.). If yours are all failing the same way (bearings), then I'd look to the belt/pulley tension/position (as it sounds like you are).

Sorry that I can't be of more help. Just wanted to share that it may not be your car that is at fault.