Fault Finding Testing for Insulation Resistance. Low Reading Insulation Resistance Fault How to test for insulation resistance inside a consumer unit. Marcus is carrying out an electrical inspection and testing when he come across a fault giving him a low reading during the insulation resistance test. These videos will help with AM2, AM2S, AM2E and your apprenticeship end point assessments. The testing and fault finding is carried out with a Megger MFT tester in controlled conditions at Tresham