JLWD1612 dryer cycle wont stay on for more than 20mins

Hi gent prod 914604700/01 when dryer selected time dry 1hr works fine but when it goes to 30mins it then finishes with 3peeps and time noen flashes all elements ok fan ok no blockages but i can only get 240v to 1 element on cotton dry does the anti crease tumble for 5mins and then door unlocks as thou its finished no fault codes on display showing can anyone help on tech for this machine and is there a test prog i can get into all the wash side works fine on any wash prog cheers alro