Fanbaelt and flat spot?

[streetboy]

Ok, I had some charge light issues which turned out to be adjustment of the fanbelt. Prior to that the bus developed a very slight flat spot, with the belt done it went. :?
I recently gave did a 300 mile round trip and noticed after a couple of days the flat spot had returned. The charge light stayed on this morning and it seems the belt had stretched again.

Fitted a new belt, charge light off, and the flat spot has gone again.

My question is, how by adjusting the belt can it effect the running so much?

 

[lard]

My guess (cause I'm no expert!) is that the "flat spot" is caused when the fan belt is slipping and not supplying charge to the battery via the alternator and hence voltage drop and ignition circuit does not have the correct/enough voltage to run efficiently - that or sone other electrical device suffering low power (fuel pump)?

 

[streetboy]

Hiya Lard yeah it must cause quite a drop in voltage on the ignition side. I never realized how critical the belt adjustment was on these engines, apart from the obvious and the cooling side of things.
Two spare belts under the seat and I'll be making regular checks now.
And its a right fiddly job and all :roll: