Refrigeration

another problem i have encountered,my howden is tripping on high oil seperator tempreture-70degrees,but my discharge tempreture from the compressor is less than that ranging around 65degrees that means inlet oil tempreture will be higherwhich will be flowing towards the compressor and then automatically it will trip on high oil tempereture.The set is 68.5degrees.my question is i can not figure out where the temreture rise is coming from in the seperator.The oil is cooled by direct ingection of ammonia from the condensorsinto the compressor.might my RTDs be not working?pliz help me with areas i can focuse on..my oil heater in the seperator is working perfectly