hi mark thanks for reply when i tested the supply to each of the heaters i checked for voltage drop/loss and there was about .5v at the hearters and that is from the heater relay to the glow plugs.

i did find that one of the heater fires had been rubbing on the air filter housing i have put some insulation tape to cover the damage to OUTER casing and routed so as not to cause any further problems.

i diddnt check the imv valve at the pump.

at the moment my customers customer has the car back to try and make the fault reocur wth the hope that infomation can be passed on as to how to make the fault show itself.