wheres my power going?

[beero]

Yes, there is something wrong if you can turn the alternator pulley and not move the belt. Looks like BMC was right!

[phurn]

Seems so, now I wonder if its the same size belt with an alternator conversion as standard....

[bmcecosse]

Told you so........ It would have taken 5 minutes to fit a NEW belt and would have saved you all the other messing about you have done.......

[phurn]

Tbh I haven't really done anything so far I wouldn't have done anyway, just cleared up a few earths and found some confusing wires. By christ the wirings bad =( there was a short aswell, as it goes. and tbf I never said you were wrong, I simply wanted to understand why, as it had always been my understanding fanbelt problems became more prevelent at high revs, not low.

[bmcecosse]

It's very definitely not right if you can turn the alternator drive pulley..........

[phurn]

I figured as much. Weirdly the belt shows no sign of age though, its not freyed at the edges, there's no cracks or smooth glazed sections. I wonder why its slipping....

[bmcecosse]

May be wrong section/glazed due to running slack/contaminated with oil/worn grooves in the pulley - or even wrong pulley on the alternator.......

[Roni]

I found the belt I needed when I put an alternator on mine was a different size to std. I guess it was down to the different pulley size on the new alternator. The std size belt would not tighten enough.

[MarkyB]

If the belt is running at the bottom of the pulley it wont work properly, it needs to be riding in the V section,with the pulley sides and making good contact with the belts sides.

Try and ascertain where wear is taking place, if it's just on the top "corners" of the belt then there isn't enough contact area.

[phurn]

what wer there is does appear to be in those top corners, so would i require a slightly thicker repalcement belt?

[MikeHA4]

A further thought on 'principles' to bear in mind, relates to belt tension when the engine is stationary. It should be possible to deflect the longest belt run between pulleys, at its middle, by up to half an inch (12mm) max. using a finger.

When the engine is running, centrifugal force will act on the belt, tending to throw it off of its pulleys, thereby reducing the friction and effective drive. So if incorrectly adjusted, they can more easily slip at speed.

[MarkyB]

would I require a slightly thicker replacement belt?

A better solution would probably be to get a pulley that matches the others, if that is the cause.
Any idea what the alternator came off? European cars use metric belts as far as I can tell.

[phurn]

i have no idea what it came off =[ was already fitted when i buaght the car. the belt also slips on the fan blade pulley aswell though so maybe its the wrong belt altogether?

[MarkyB]

You can get a belt to suit a Minor with an alternator from the normal suppliers.
As MikeHA4 says the belt shouldn't be bar tight, that just wears the belt and bearings faster than necessary.