Indesit is7oc takes ages to dry clothes?

I've noticed recently that the heat is low although the switch is on high. I've tryed resetting the thermo switch but it's ok.What i've noticed is when i remove the fan cover and switch it on (i know this is dangerous but i'm extremely carefull) the four elements light up to full heat. But as i slowely replace it,the two elements nearer the fan go out.It seems like a loose connection but i've tried all the cables and they're tight. HELP !! i'm going mad.