My vivaro 2007 blow heater works good when the van is cold but if you turn the engine off and back on when the engine has warmed up the blow heater will not work , you have to pop the bonnet and give the blower unit a VERY light tap and it comes on straight away ... Can anybody help
the fact you have to give it a tap when it`s hot may be your clue,you may have a sticky bush which may expand when hot slightly,enough to seize up motor or a faulty electrical connection,if you can see any bearings/bushes try giving them a lube,also check electrical connections are clean.