6B belt spring tensioner mystery

[Robert Cart]

I have an old (circa 1994) 6B5.9M. When I went to replace the alternator, I discovered that the spring tensioner is on the loaded side of the alternator. From memory and the specs, the engine should be turning clockwise when facing the front of the engine, i.e. the crankshaft and alternator end. Take a look at the attached. The belt is removed in the photo but if you look to the right of the alternator you’ll see the spring tensioner there. I believe that’s the loaded side and the tensioner needs to be moved under the alternator to the left of the crankshaft.

Does anyone have any advise about this? Any photos of the correct way to mount it? Any ideas about what to bolt it to? Any clues about why it was installed incorrectly? The old alternator was installed without any tension adjustment so the tensioner at least served that role. However, I also found a lot of belt dust which I can imagine could be caused by the improper tensioner mounting. Any ideas or clues appreciated.

Topic

[Tony Athens]

The “system” is generally reliable and overall trouble free.. Removing the belt and checking this every 2-3 years or every 1000 hours would be prudent with replacement of everything that spins at 2000 hours intervals should be considered. In a car, 2000 hours at an average speed of just 30 MPH is 60,000 miles..

Tony

[Robert Cart]

Thanks, Tony. The photo you sent is what I have. This means it os intentional for the tensioner to be on the loaded side of the crankshaft. That means it is only making the belt tight enough most of the time. However, sometimes, especially with a rapid disengage of a high output alternator, the load can drop fast enough to cause slack on the unloaded side which can whip and reduce belt life. However, I am happy to just assume all is well with this design especially considering the zillions of them put is service. Cheers!

[Tony Athens]

Proper belt wrap pic attached.. Looking at the crankshaft, CW is its rotating.

Tony

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