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I got recovered home by the RAC as they did not know what sort of belt it was. 
I can see how to change the alteernator belt but cannot see a tensioner on the other one. Any tips or advice would be great as I need to get it fixed for Trax The other belt is for the aircon and the power-steering pump is electrically driven and is situated in the front boot. The tensioner for the aircon is the little wheel at the top of the belt. You slacken the bolt in the centre of the tensioner wheel (don't take it out just slacken it a couple of turns) then unscrew the bolt just behind the wheel on the holding bracket. You'll see the bolt as it is on the same vertical centre as the tensioner wheel. Then, as you slacken this bolt, you will see the tensioner wheel move downwards as you turn, thus slackening the belt. (note the direction so you can replace it the same way around). Fit new alternator belt and refit aircon belt and retension. When you are retensioning the aircon belt, tighten the tensioner-wheel centre bolt so it's just meeting the wheel, in other words no slack between bolt and wheel. Because if you have slack then you set the belt to the right tension, but the wheel will be at a slight angle. So when you come to tighten the centre nut it will tighten the tension even more and could overtension the belt. So you don't want the wheel flopping about when you are tensioning the belt. Make sure both the top and bottom fasteners are done right up when you are tensioning the belt. But not tight, obviously, as the alternator wont move. Then, when it's tensioned, you just nip up the bolts. sall i just leave this one alone? go befire i pay a garage to do it! 
But, then again, if your alternator belt is really slack then it will not squeal. It just simply will not transmit the rotary movement of the crank pulley to alternator pulley. It'll just be flapping around like nobody's business and, at some stage, it will disintegrate for various reasons that are difficult to put into words. Then, adjust the top tensioner. If you can move it up and down by about a centimetre (without going into all the specifics laid down by Toyota) that's "about" right. If it still squeals at this tension then the belt or the alternator is f*cked. got worse, and then it must have got so slack, it doesnt even squeel now.., ? is this right? sorry for being a pain! Just need to get a part number as I bet Toyota charge a fortune.loosen the top and bottom alternator mounting bolts. Don't take them out just slacken them them off a turn. Now, go to the tensioner and release the locknut and begin tensioning the belt. You need to tighten the belt to a particular spec using a belt-tension gauge. Then tighten the alternator mounting bolts. Now take up the tiny amount of slack that will appear on the tensioner bolt and tighten the tensioner bolt locknut. Then put the wheel back on. http://www.ayrpark.plus.com/epc/toyota/ ... 01_19.htmlhttp://www.ayrpark.plus.com/epc/mr2epc.html Can't remember who posted it up originally, but it's been a godsend to me when rebuilding my engine.