Alernator/charging light coming on dimmly

if suggestion by my fixya collegue shows vm reading at 14v check belt tension before proceeding

may i suggest you test the charge to battery using volt meter should be around 14 volts if alt is working ok also check the wires and connections to alternator are clean and secure? if alternator is faulty it is reasonably eay diy to change and you can obtain yourself from motor store if you have local tyre/battery depot near you pop along and have them check alt output/condition if you have no v/meter? they normally do not charge here in uk for quick check if they are not busy hope this helps